[v6,4/4] colo: Update Documentation for continuous replication

Commit Message

Lukas Straub Oct. 5, 2019, 1:05 p.m. UTC

Document the qemu command-line and qmp commands for continuous replication

Signed-off-by: Lukas Straub <[e-mail]>
---
 docs/COLO-FT.txt           | 213 +++++++++++++++++++++++++++----------
 docs/block-replication.txt |  28 +++--
 2 files changed, 174 insertions(+), 67 deletions(-)

Comments

Zhang Chen Oct. 9, 2019, 8:36 a.m. UTC | #1

> -----Original Message-----
> From: Lukas Straub <[e-mail]>
> Sent: Saturday, October 5, 2019 9:06 PM
> To: qemu-devel <[e-mail]>
> Cc: Zhang, Chen <[e-mail]>; Jason Wang
> <[e-mail]>; Wen Congyang <[e-mail]>;
> Xie Changlong <[e-mail]>; Kevin Wolf
> <[e-mail]>; Max Reitz <[e-mail]>; qemu-block
> <[e-mail]>
> Subject: [PATCH v6 4/4] colo: Update Documentation for continuous
> replication
> 
> Document the qemu command-line and qmp commands for continuous
> replication
> 
> Signed-off-by: Lukas Straub <[e-mail]>
> ---
>  docs/COLO-FT.txt           | 213 +++++++++++++++++++++++++++----------
>  docs/block-replication.txt |  28 +++--
>  2 files changed, 174 insertions(+), 67 deletions(-)
> 
> diff --git a/docs/COLO-FT.txt b/docs/COLO-FT.txt index
> ad24680d13..bc1a0ccb99 100644
> --- a/docs/COLO-FT.txt
> +++ b/docs/COLO-FT.txt
> @@ -145,35 +145,65 @@ The diagram just shows the main qmp command,
> you can get the detail  in test procedure.
> 
>  == Test procedure ==
> -1. Startup qemu
> -Primary:
> -# qemu-system-x86_64 -accel kvm -m 2048 -smp 2 -qmp stdio -name
> primary \
> -  -device piix3-usb-uhci -vnc :7 \
> -  -device usb-tablet -netdev tap,id=hn0,vhost=off \
> -  -device virtio-net-pci,id=net-pci0,netdev=hn0 \
> -  -drive if=virtio,id=primary-disk0,driver=quorum,read-pattern=fifo,vote-
> threshold=1,\
> -         children.0.file.filename=1.raw,\
> -         children.0.driver=raw -S
> -Secondary:
> -# qemu-system-x86_64 -accel kvm -m 2048 -smp 2 -qmp stdio -name
> secondary \
> -  -device piix3-usb-uhci -vnc :7 \
> -  -device usb-tablet -netdev tap,id=hn0,vhost=off \
> -  -device virtio-net-pci,id=net-pci0,netdev=hn0 \
> -  -drive if=none,id=secondary-disk0,file.filename=1.raw,driver=raw,node-
> name=node0 \
> -  -drive if=virtio,id=active-disk0,driver=replication,mode=secondary,\
> -         file.driver=qcow2,top-id=active-disk0,\
> -         file.file.filename=/mnt/ramfs/active_disk.img,\
> -         file.backing.driver=qcow2,\
> -         file.backing.file.filename=/mnt/ramfs/hidden_disk.img,\
> -         file.backing.backing=secondary-disk0 \
> -  -incoming tcp:0:8888
> -
> -2. On Secondary VM's QEMU monitor, issue command
> +Note: Here we are running both instances on the same Host for testing,
> +change the IP Addresses if you want to run it on two Hosts. Initally
> +127.0.0.1 is the Primary Host and 127.0.0.2 is the Secondary Host.
> +
> +== Startup qemu ==
> +1. Primary:
> +Note: Initally, $imagefolder/primary.qcow2 needs to be copied to all Hosts.
> +# imagefolder="/mnt/vms/colo-test-primary"
> +
> +# qemu-system-x86_64 -enable-kvm -cpu qemu64,+kvmclock -m 512 -smp
> 1 -qmp stdio \
> +   -device piix3-usb-uhci -device usb-tablet -name primary \
> +   -netdev tap,id=hn0,vhost=off,helper=/usr/lib/qemu/qemu-bridge-helper
> \
> +   -device rtl8139,id=e0,netdev=hn0 \
> +   -chardev socket,id=mirror0,host=0.0.0.0,port=9003,server,nowait \
> +   -chardev socket,id=compare1,host=0.0.0.0,port=9004,server,wait \

We should change the host=127.0.0.1 consistent with the expression below.

> +   -chardev socket,id=compare0,host=127.0.0.1,port=9001,server,nowait \
> +   -chardev socket,id=compare0-0,host=127.0.0.1,port=9001 \
> +   -chardev socket,id=compare_out,host=127.0.0.1,port=9005,server,nowait
> \
> +   -chardev socket,id=compare_out0,host=127.0.0.1,port=9005 \
> +   -object filter-mirror,id=m0,netdev=hn0,queue=tx,outdev=mirror0 \
> +   -object filter-
> redirector,netdev=hn0,id=redire0,queue=rx,indev=compare_out \
> +   -object filter-
> redirector,netdev=hn0,id=redire1,queue=rx,outdev=compare0 \
> +   -object iothread,id=iothread1 \
> +   -object
> +colo-compare,id=comp0,primary_in=compare0-
> 0,secondary_in=compare1,\
> +outdev=compare_out0,iothread=iothread1 \
> +   -drive
> +if=ide,id=colo-disk0,driver=quorum,read-pattern=fifo,vote-threshold=1,\
> +children.0.file.filename=$imagefolder/primary.qcow2,children.0.driver=q
> +cow2 -S
> +
> +2. Secondary:
> +# imagefolder="/mnt/vms/colo-test-secondary"
> +# primary_ip=127.0.0.1
> +
> +# qemu-img create -f qcow2 $imagefolder/secondary-active.qcow2 10G
> +
> +# qemu-img create -f qcow2 $imagefolder/secondary-hidden.qcow2 10G
> +

The active disk and hidden disk just need create one time, we can note that here.

> +# qemu-system-x86_64 -enable-kvm -cpu qemu64,+kvmclock -m 512 -smp
> 1 -qmp stdio \
> +   -device piix3-usb-uhci -device usb-tablet -name secondary \
> +   -netdev tap,id=hn0,vhost=off,helper=/usr/lib/qemu/qemu-bridge-helper
> \
> +   -device rtl8139,id=e0,netdev=hn0 \
> +   -chardev socket,id=red0,host=$primary_ip,port=9003,reconnect=1 \
> +   -chardev socket,id=red1,host=$primary_ip,port=9004,reconnect=1 \
> +   -object filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0 \
> +   -object filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1 \
> +   -object filter-rewriter,id=rew0,netdev=hn0,queue=all \
> +   -drive
> if=none,id=parent0,file.filename=$imagefolder/primary.qcow2,driver=qcow
> 2 \
> +   -drive
> +if=none,id=childs0,driver=replication,mode=secondary,file.driver=qcow2,
> +\
> +top-id=childs0,file.file.filename=$imagefolder/secondary-active.qcow2,\
> +file.backing.driver=qcow2,file.backing.file.filename=$imagefolder/secon
> +dary-hidden.qcow2,\
> +file.backing.backing=parent0 \
> +   -drive
> +if=ide,id=colo-disk0,driver=quorum,read-pattern=fifo,vote-threshold=1,\
> +children.0=childs0 \
> +   -incoming tcp:0.0.0.0:9998
> +
> +
> +3. On Secondary VM's QEMU monitor, issue command
>  {'execute':'qmp_capabilities'}
> -{ 'execute': 'nbd-server-start',
> -  'arguments': {'addr': {'type': 'inet', 'data': {'host': 'xx.xx.xx.xx', 'port':
> '8889'} } } -}
> -{'execute': 'nbd-server-add', 'arguments': {'device': 'secondary-disk0',
> 'writable': true } }
> +{'execute': 'nbd-server-start', 'arguments': {'addr': {'type': 'inet',
> +'data': {'host': '0.0.0.0', 'port': '9999'} } } }
> +{'execute': 'nbd-server-add', 'arguments': {'device': 'parent0',
> +'writable': true } }
> 
>  Note:
>    a. The qmp command nbd-server-start and nbd-server-add must be run
> @@ -182,44 +212,113 @@ Note:
>       same.
>    c. It is better to put active disk and hidden disk in ramdisk.
> 
> -3. On Primary VM's QEMU monitor, issue command:
> +4. On Primary VM's QEMU monitor, issue command:
>  {'execute':'qmp_capabilities'}
> -{ 'execute': 'human-monitor-command',
> -  'arguments': {'command-line': 'drive_add -n buddy
> driver=replication,mode=primary,file.driver=nbd,file.host=xx.xx.xx.xx,file.p
> ort=8889,file.export=secondary-disk0,node-name=nbd_client0'}}
> -{ 'execute':'x-blockdev-change', 'arguments':{'parent': 'primary-disk0',
> 'node': 'nbd_client0' } } -{ 'execute': 'migrate-set-capabilities',
> -      'arguments': {'capabilities': [ {'capability': 'x-colo', 'state': true } ] } }
> -{ 'execute': 'migrate', 'arguments': {'uri': 'tcp:xx.xx.xx.xx:8888' } }
> +{'execute': 'human-monitor-command', 'arguments': {'command-line':
> +'drive_add -n buddy
> +driver=replication,mode=primary,file.driver=nbd,file.host=127.0.0.2,fil
> +e.port=9999,file.export=parent0,node-name=replication0'}}
> +{'execute': 'x-blockdev-change', 'arguments':{'parent': 'colo-disk0',
> +'node': 'replication0' } }
> +{'execute': 'migrate-set-capabilities', 'arguments': {'capabilities': [
> +{'capability': 'x-colo', 'state': true } ] } }
> +{'execute': 'migrate', 'arguments': {'uri': 'tcp:127.0.0.2:9998' } }
> 
>    Note:
>    a. There should be only one NBD Client for each primary disk.
> -  b. xx.xx.xx.xx is the secondary physical machine's hostname or IP
> -  c. The qmp command line must be run after running qmp command line in
> +  b. The qmp command line must be run after running qmp command line in
>       secondary qemu.
> 
> -4. After the above steps, you will see, whenever you make changes to PVM,
> SVM will be synced.
> +5. After the above steps, you will see, whenever you make changes to PVM,
> SVM will be synced.
>  You can issue command '{ "execute": "migrate-set-parameters" ,
> "arguments":{ "x-checkpoint-delay": 2000 } }'
> -to change the checkpoint period time
> +to change the idle checkpoint period time
> +
> +6. Failover test
> +You can kill one of the VMs and Failover on the surviving VM:
> +
> +If you killed the Secondary, then follow "Primary Failover". After
> +that, if you want to resume the replication, follow "Primary resume
> replication"
> +
> +If you killed the Primary, then follow "Secondary Failover". After
> +that, if you want to resume the replication, follow "Secondary resume
> replication"
> +
> +== Primary Failover ==
> +The Secondary died, resume on the Primary
> +
> +{'execute': 'x-blockdev-change', 'arguments':{ 'parent': 'colo-disk0',
> +'child': 'children.1'} }
> +{'execute': 'human-monitor-command', 'arguments':{ 'command-line':
> +'drive_del replication0' } }
> +{'execute': 'object-del', 'arguments':{ 'id': 'comp0' } }
> +{'execute': 'object-del', 'arguments':{ 'id': 'iothread1' } }
> +{'execute': 'object-del', 'arguments':{ 'id': 'm0' } }
> +{'execute': 'object-del', 'arguments':{ 'id': 'redire0' } }
> +{'execute': 'object-del', 'arguments':{ 'id': 'redire1' } }
> +{'execute': 'x-colo-lost-heartbeat' }
> +
> +== Secondary Failover ==
> +The Primary died, resume on the Secondary and prepare to become the
> new
> +Primary
> +
> +{'execute': 'nbd-server-stop'}
> +{'execute': 'x-colo-lost-heartbeat'}
> +
> +{'execute': 'object-del', 'arguments':{ 'id': 'f2' } }
> +{'execute': 'object-del', 'arguments':{ 'id': 'f1' } }
> +{'execute': 'chardev-remove', 'arguments':{ 'id': 'red1' } }
> +{'execute': 'chardev-remove', 'arguments':{ 'id': 'red0' } }
> +
> +{'execute': 'chardev-add', 'arguments':{ 'id': 'mirror0', 'backend':
> +{'type': 'socket', 'data': {'addr': { 'type': 'inet', 'data': { 'host':
> +'0.0.0.0', 'port': '9003' } }, 'server': true } } } }

Same like I said before.

Others statement looks good for me.

Thanks
Zhang Chen

> +{'execute': 'chardev-add', 'arguments':{ 'id': 'compare1', 'backend':
> +{'type': 'socket', 'data': {'addr': { 'type': 'inet', 'data': { 'host':
> +'0.0.0.0', 'port': '9004' } }, 'server': true } } } }
> +{'execute': 'chardev-add', 'arguments':{ 'id': 'compare0', 'backend':
> +{'type': 'socket', 'data': {'addr': { 'type': 'inet', 'data': { 'host':
> +'127.0.0.1', 'port': '9001' } }, 'server': true } } } }
> +{'execute': 'chardev-add', 'arguments':{ 'id': 'compare0-0', 'backend':
> +{'type': 'socket', 'data': {'addr': { 'type': 'inet', 'data': { 'host':
> +'127.0.0.1', 'port': '9001' } }, 'server': false } } } }
> +{'execute': 'chardev-add', 'arguments':{ 'id': 'compare_out',
> +'backend': {'type': 'socket', 'data': {'addr': { 'type': 'inet',
> +'data': { 'host': '127.0.0.1', 'port': '9005' } }, 'server': true } } }
> +}
> +{'execute': 'chardev-add', 'arguments':{ 'id': 'compare_out0',
> +'backend': {'type': 'socket', 'data': {'addr': { 'type': 'inet',
> +'data': { 'host': '127.0.0.1', 'port': '9005' } }, 'server': false } }
> +} }
> +
> +== Primary resume replication ==
> +Resume replication after new Secondary is up.
> +
> +Start the new Secondary (Steps 2 and 3 above), then on the Primary:
> +{'execute': 'drive-mirror', 'arguments':{ 'device': 'colo-disk0',
> +'job-id': 'resync', 'target': 'nbd://127.0.0.2:9999/parent0', 'mode':
> +'existing', 'format': 'raw', 'sync': 'full'} }
> +
> +Wait until disk is synced, then:
> +{'execute': 'stop'}
> +{'execute': 'block-job-cancel', 'arguments':{ 'device': 'resync'} }
> +
> +{'execute': 'human-monitor-command', 'arguments':{ 'command-line':
> +'drive_add -n buddy
> +driver=replication,mode=primary,file.driver=nbd,file.host=127.0.0.2,fil
> +e.port=9999,file.export=parent0,node-name=replication0'}}
> +{'execute': 'x-blockdev-change', 'arguments':{ 'parent': 'colo-disk0',
> +'node': 'replication0' } }
> +
> +{'execute': 'object-add', 'arguments':{ 'qom-type': 'filter-mirror',
> +'id': 'm0', 'props': { 'netdev': 'hn0', 'queue': 'tx', 'outdev':
> +'mirror0' } } }
> +{'execute': 'object-add', 'arguments':{ 'qom-type':
> +'filter-redirector', 'id': 'redire0', 'props': { 'netdev': 'hn0',
> +'queue': 'rx', 'indev': 'compare_out' } } }
> +{'execute': 'object-add', 'arguments':{ 'qom-type':
> +'filter-redirector', 'id': 'redire1', 'props': { 'netdev': 'hn0',
> +'queue': 'rx', 'outdev': 'compare0' } } }
> +{'execute': 'object-add', 'arguments':{ 'qom-type': 'iothread', 'id':
> +'iothread1' } }
> +{'execute': 'object-add', 'arguments':{ 'qom-type': 'colo-compare',
> +'id': 'comp0', 'props': { 'primary_in': 'compare0-0', 'secondary_in':
> +'compare1', 'outdev': 'compare_out0', 'iothread': 'iothread1' } } }
> +
> +{'execute': 'migrate-set-capabilities', 'arguments':{ 'capabilities': [
> +{'capability': 'x-colo', 'state': true } ] } }
> +{'execute': 'migrate', 'arguments':{ 'uri': 'tcp:127.0.0.2:9998' } }
> +
> +Note:
> +If this Primary previously was a Secondary, then we need to insert the
> +filters before the filter-rewriter by using the
> +"'insert': 'before', 'position': 'id=rew0'" Options. See below.
> +
> +== Secondary resume replication ==
> +Become Primary and resume replication after new Secondary is up. Note
> +that now 127.0.0.1 is the Secondary and 127.0.0.2 is the Primary.
> +
> +Start the new Secondary (Steps 2 and 3 above, but with
> +primary_ip=127.0.0.2), then on the old Secondary:
> +{'execute': 'drive-mirror', 'arguments':{ 'device': 'colo-disk0',
> +'job-id': 'resync', 'target': 'nbd://127.0.0.1:9999/parent0', 'mode':
> +'existing', 'format': 'raw', 'sync': 'full'} }
> +
> +Wait until disk is synced, then:
> +{'execute': 'stop'}
> +{'execute': 'block-job-cancel', 'arguments':{ 'device': 'resync' } }
> 
> -5. Failover test
> -You can kill Primary VM and run 'x_colo_lost_heartbeat' in Secondary VM's -
> monitor at the same time, then SVM will failover and client will not detect
> this -change.
> +{'execute': 'human-monitor-command', 'arguments':{ 'command-line':
> +'drive_add -n buddy
> +driver=replication,mode=primary,file.driver=nbd,file.host=127.0.0.1,fil
> +e.port=9999,file.export=parent0,node-name=replication0'}}
> +{'execute': 'x-blockdev-change', 'arguments':{ 'parent': 'colo-disk0',
> +'node': 'replication0' } }
> 
> -Before issuing '{ "execute": "x-colo-lost-heartbeat" }' command, we have to
> -issue block related command to stop block replication.
> -Primary:
> -  Remove the nbd child from the quorum:
> -  { 'execute': 'x-blockdev-change', 'arguments': {'parent': 'colo-disk0', 'child':
> 'children.1'}}
> -  { 'execute': 'human-monitor-command','arguments': {'command-line':
> 'drive_del blk-buddy0'}}
> -  Note: there is no qmp command to remove the blockdev now
> +{'execute': 'object-add', 'arguments':{ 'qom-type': 'filter-mirror',
> +'id': 'm0', 'props': { 'insert': 'before', 'position': 'id=rew0',
> +'netdev': 'hn0', 'queue': 'tx', 'outdev': 'mirror0' } } }
> +{'execute': 'object-add', 'arguments':{ 'qom-type':
> +'filter-redirector', 'id': 'redire0', 'props': { 'insert': 'before',
> +'position': 'id=rew0', 'netdev': 'hn0', 'queue': 'rx', 'indev':
> +'compare_out' } } }
> +{'execute': 'object-add', 'arguments':{ 'qom-type':
> +'filter-redirector', 'id': 'redire1', 'props': { 'insert': 'before',
> +'position': 'id=rew0', 'netdev': 'hn0', 'queue': 'rx', 'outdev':
> +'compare0' } } }
> +{'execute': 'object-add', 'arguments':{ 'qom-type': 'iothread', 'id':
> +'iothread1' } }
> +{'execute': 'object-add', 'arguments':{ 'qom-type': 'colo-compare',
> +'id': 'comp0', 'props': { 'primary_in': 'compare0-0', 'secondary_in':
> +'compare1', 'outdev': 'compare_out0', 'iothread': 'iothread1' } } }
> 
> -Secondary:
> -  The primary host is down, so we should do the following thing:
> -  { 'execute': 'nbd-server-stop' }
> +{'execute': 'migrate-set-capabilities', 'arguments':{ 'capabilities': [
> +{'capability': 'x-colo', 'state': true } ] } }
> +{'execute': 'migrate', 'arguments':{ 'uri': 'tcp:127.0.0.1:9998' } }
> 
>  == TODO ==
> -1. Support continuous VM replication.
> -2. Support shared storage.
> -3. Develop the heartbeat part.
> -4. Reduce checkpoint VM’s downtime while doing checkpoint.
> +1. Support shared storage.
> +2. Develop the heartbeat part.
> +3. Reduce checkpoint VM’s downtime while doing checkpoint.
> diff --git a/docs/block-replication.txt b/docs/block-replication.txt index
> 6bde6737fb..108e9166a8 100644
> --- a/docs/block-replication.txt
> +++ b/docs/block-replication.txt
> @@ -65,12 +65,12 @@ blocks that are already in QEMU.
>               ^            ||                            .----------
>               |            ||                            | Secondary
>          1 Quorum          ||                            '----------
> -         /      \         ||
> -        /        \        ||
> -   Primary    2 filter
> -     disk         ^                                                             virtio-blk
> -                  |                                                                  ^
> -                3 NBD  ------->  3 NBD                                               |
> +         /      \         ||                                                           virtio-blk
> +        /        \        ||                                                               ^
> +   Primary    2 filter                                                                     |
> +     disk         ^                                                                   7 Quorum
> +                  |                                                                    /
> +                3 NBD  ------->  3 NBD                                                /
>                  client    ||     server                                          2 filter
>                            ||        ^                                                ^
>  --------.                 ||        |                                                |
> @@ -106,6 +106,10 @@ any state that would otherwise be lost by the
> speculative write-through  of the NBD server into the secondary disk. So
> before block replication,  the primary disk and secondary disk should contain
> the same data.
> 
> +7) The secondary also has a quorum node, so after secondary failover it
> +can become the new primary and continue replication.
> +
> +
>  == Failure Handling ==
>  There are 7 internal errors when block replication is running:
>  1. I/O error on primary disk
> @@ -171,16 +175,18 @@ Primary:
>       leading whitespace.
>    5. The qmp command line must be run after running qmp command line in
>       secondary qemu.
> -  6. After failover we need remove children.1 (replication driver).
> +  6. After primary failover we need remove children.1 (replication driver).
> 
>  Secondary:
>    -drive if=none,driver=raw,file.filename=1.raw,id=colo1 \
> -  -drive if=xxx,id=topxxx,driver=replication,mode=secondary,top-
> id=topxxx\
> +  -drive
> + if=none,id=childs1,driver=replication,mode=secondary,top-id=childs1
>           file.file.filename=active_disk.qcow2,\
>           file.driver=qcow2,\
>           file.backing.file.filename=hidden_disk.qcow2,\
>           file.backing.driver=qcow2,\
>           file.backing.backing=colo1
> +  -drive if=xxx,driver=quorum,read-pattern=fifo,id=top-disk1,\
> +         vote-threshold=1,children.0=childs1
> 
>    Then run qmp command in secondary qemu:
>      { 'execute': 'nbd-server-start',
> @@ -234,6 +240,8 @@ Secondary:
>    The primary host is down, so we should do the following thing:
>    { 'execute': 'nbd-server-stop' }
> 
> +Promote Secondary to Primary:
> +  see COLO-FT.txt
> +
>  TODO:
> -1. Continuous block replication
> -2. Shared disk
> +1. Shared disk
> --
> 2.20.1

Lukas Straub Oct. 9, 2019, 3:16 p.m. UTC | #2

On Wed, 9 Oct 2019 08:36:52 +0000
"Zhang, Chen" <[e-mail]> wrote:

> > -----Original Message-----
> > From: Lukas Straub <[e-mail]>
> > Sent: Saturday, October 5, 2019 9:06 PM
> > To: qemu-devel <[e-mail]>
> > Cc: Zhang, Chen <[e-mail]>; Jason Wang
> > <[e-mail]>; Wen Congyang <[e-mail]>;
> > Xie Changlong <[e-mail]>; Kevin Wolf
> > <[e-mail]>; Max Reitz <[e-mail]>; qemu-block
> > <[e-mail]>
> > Subject: [PATCH v6 4/4] colo: Update Documentation for continuous
> > replication
> > 
> > Document the qemu command-line and qmp commands for continuous
> > replication
> > 
> > Signed-off-by: Lukas Straub <[e-mail]>
> > ---
> >  docs/COLO-FT.txt           | 213 +++++++++++++++++++++++++++----------
> >  docs/block-replication.txt |  28 +++--
> >  2 files changed, 174 insertions(+), 67 deletions(-)
> > 
> > diff --git a/docs/COLO-FT.txt b/docs/COLO-FT.txt index
> > ad24680d13..bc1a0ccb99 100644
> > --- a/docs/COLO-FT.txt
> > +++ b/docs/COLO-FT.txt
> > @@ -145,35 +145,65 @@ The diagram just shows the main qmp command,
> > you can get the detail  in test procedure.
> > 
> > ...
> >
> > +Note: Here we are running both instances on the same Host for testing,
> > +change the IP Addresses if you want to run it on two Hosts. Initally
> > +127.0.0.1 is the Primary Host and 127.0.0.2 is the Secondary Host.
> > +
> > +== Startup qemu ==
> > +1. Primary:
> > +Note: Initally, $imagefolder/primary.qcow2 needs to be copied to all Hosts.
> > +# imagefolder="/mnt/vms/colo-test-primary"
> > +
> > +# qemu-system-x86_64 -enable-kvm -cpu qemu64,+kvmclock -m 512 -smp
> > 1 -qmp stdio \
> > +   -device piix3-usb-uhci -device usb-tablet -name primary \
> > +   -netdev tap,id=hn0,vhost=off,helper=/usr/lib/qemu/qemu-bridge-helper
> > \
> > +   -device rtl8139,id=e0,netdev=hn0 \
> > +   -chardev socket,id=mirror0,host=0.0.0.0,port=9003,server,nowait \
> > +   -chardev socket,id=compare1,host=0.0.0.0,port=9004,server,wait \  
> 
> We should change the host=127.0.0.1 consistent with the expression below.

Hi,
This (and the IPs below in the QMP commands) needs to be this way, because 
it's a listening port and with 127.0.0.1 it would only listen on the loopback ip
and wouldn't be reachable from another node for example. With 0.0.0.0 it will
listen on all Interfaces.

> > +   -chardev socket,id=compare0,host=127.0.0.1,port=9001,server,nowait \
> > +   -chardev socket,id=compare0-0,host=127.0.0.1,port=9001 \
> > +   -chardev socket,id=compare_out,host=127.0.0.1,port=9005,server,nowait
> > \
> > +   -chardev socket,id=compare_out0,host=127.0.0.1,port=9005 \
> > +   -object filter-mirror,id=m0,netdev=hn0,queue=tx,outdev=mirror0 \
> > +   -object filter-
> > redirector,netdev=hn0,id=redire0,queue=rx,indev=compare_out \
> > +   -object filter-
> > redirector,netdev=hn0,id=redire1,queue=rx,outdev=compare0 \
> > +   -object iothread,id=iothread1 \
> > +   -object
> > +colo-compare,id=comp0,primary_in=compare0-
> > 0,secondary_in=compare1,\
> > +outdev=compare_out0,iothread=iothread1 \
> > +   -drive
> > +if=ide,id=colo-disk0,driver=quorum,read-pattern=fifo,vote-threshold=1,\
> > +children.0.file.filename=$imagefolder/primary.qcow2,children.0.driver=q
> > +cow2 -S
> > +
> > +2. Secondary:
> > +# imagefolder="/mnt/vms/colo-test-secondary"
> > +# primary_ip=127.0.0.1
> > +
> > +# qemu-img create -f qcow2 $imagefolder/secondary-active.qcow2 10G
> > +
> > +# qemu-img create -f qcow2 $imagefolder/secondary-hidden.qcow2 10G
> > +  
> 
> The active disk and hidden disk just need create one time, we can note that here.

Ok, I will Note that. But I will wait until the block changes are reviewed before sending the next version.

Regards,
Lukas Straub

> > +# qemu-system-x86_64 -enable-kvm -cpu qemu64,+kvmclock -m 512 -smp
> > 1 -qmp stdio \
> > +   -device piix3-usb-uhci -device usb-tablet -name secondary \
> > +   -netdev tap,id=hn0,vhost=off,helper=/usr/lib/qemu/qemu-bridge-helper
> > \
> > +   -device rtl8139,id=e0,netdev=hn0 \
> > +   -chardev socket,id=red0,host=$primary_ip,port=9003,reconnect=1 \
> > +   -chardev socket,id=red1,host=$primary_ip,port=9004,reconnect=1 \
> > +   -object filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0 \
> > +   -object filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1 \
> > +   -object filter-rewriter,id=rew0,netdev=hn0,queue=all \
> > +   -drive
> > if=none,id=parent0,file.filename=$imagefolder/primary.qcow2,driver=qcow
> > 2 \
> > +   -drive
> > +if=none,id=childs0,driver=replication,mode=secondary,file.driver=qcow2,
> > +\
> > +top-id=childs0,file.file.filename=$imagefolder/secondary-active.qcow2,\
> > +file.backing.driver=qcow2,file.backing.file.filename=$imagefolder/secon
> > +dary-hidden.qcow2,\
> > +file.backing.backing=parent0 \
> > +   -drive
> > +if=ide,id=colo-disk0,driver=quorum,read-pattern=fifo,vote-threshold=1,\
> > +children.0=childs0 \
> > +   -incoming tcp:0.0.0.0:9998
> > +
> > +
> > +3. On Secondary VM's QEMU monitor, issue command
> >  {'execute':'qmp_capabilities'}
> > -{ 'execute': 'nbd-server-start',
> > -  'arguments': {'addr': {'type': 'inet', 'data': {'host': 'xx.xx.xx.xx', 'port':
> > '8889'} } } -}
> > -{'execute': 'nbd-server-add', 'arguments': {'device': 'secondary-disk0',
> > 'writable': true } }
> > +{'execute': 'nbd-server-start', 'arguments': {'addr': {'type': 'inet',
> > +'data': {'host': '0.0.0.0', 'port': '9999'} } } }
> > +{'execute': 'nbd-server-add', 'arguments': {'device': 'parent0',
> > +'writable': true } }
> > 
> >  Note:
> >    a. The qmp command nbd-server-start and nbd-server-add must be run
> > @@ -182,44 +212,113 @@ Note:
> >       same.
> >    c. It is better to put active disk and hidden disk in ramdisk.
> > 
> > -3. On Primary VM's QEMU monitor, issue command:
> > +4. On Primary VM's QEMU monitor, issue command:
> >  {'execute':'qmp_capabilities'}
> > -{ 'execute': 'human-monitor-command',
> > -  'arguments': {'command-line': 'drive_add -n buddy
> > driver=replication,mode=primary,file.driver=nbd,file.host=xx.xx.xx.xx,file.p
> > ort=8889,file.export=secondary-disk0,node-name=nbd_client0'}}
> > -{ 'execute':'x-blockdev-change', 'arguments':{'parent': 'primary-disk0',
> > 'node': 'nbd_client0' } } -{ 'execute': 'migrate-set-capabilities',
> > -      'arguments': {'capabilities': [ {'capability': 'x-colo', 'state': true } ] } }
> > -{ 'execute': 'migrate', 'arguments': {'uri': 'tcp:xx.xx.xx.xx:8888' } }
> > +{'execute': 'human-monitor-command', 'arguments': {'command-line':
> > +'drive_add -n buddy
> > +driver=replication,mode=primary,file.driver=nbd,file.host=127.0.0.2,fil
> > +e.port=9999,file.export=parent0,node-name=replication0'}}
> > +{'execute': 'x-blockdev-change', 'arguments':{'parent': 'colo-disk0',
> > +'node': 'replication0' } }
> > +{'execute': 'migrate-set-capabilities', 'arguments': {'capabilities': [
> > +{'capability': 'x-colo', 'state': true } ] } }
> > +{'execute': 'migrate', 'arguments': {'uri': 'tcp:127.0.0.2:9998' } }
> > 
> >    Note:
> >    a. There should be only one NBD Client for each primary disk.
> > -  b. xx.xx.xx.xx is the secondary physical machine's hostname or IP
> > -  c. The qmp command line must be run after running qmp command line in
> > +  b. The qmp command line must be run after running qmp command line in
> >       secondary qemu.
> > 
> > -4. After the above steps, you will see, whenever you make changes to PVM,
> > SVM will be synced.
> > +5. After the above steps, you will see, whenever you make changes to PVM,
> > SVM will be synced.
> >  You can issue command '{ "execute": "migrate-set-parameters" ,
> > "arguments":{ "x-checkpoint-delay": 2000 } }'
> > -to change the checkpoint period time
> > +to change the idle checkpoint period time
> > +
> > +6. Failover test
> > +You can kill one of the VMs and Failover on the surviving VM:
> > +
> > +If you killed the Secondary, then follow "Primary Failover". After
> > +that, if you want to resume the replication, follow "Primary resume
> > replication"
> > +
> > +If you killed the Primary, then follow "Secondary Failover". After
> > +that, if you want to resume the replication, follow "Secondary resume
> > replication"
> > +
> > +== Primary Failover ==
> > +The Secondary died, resume on the Primary
> > +
> > +{'execute': 'x-blockdev-change', 'arguments':{ 'parent': 'colo-disk0',
> > +'child': 'children.1'} }
> > +{'execute': 'human-monitor-command', 'arguments':{ 'command-line':
> > +'drive_del replication0' } }
> > +{'execute': 'object-del', 'arguments':{ 'id': 'comp0' } }
> > +{'execute': 'object-del', 'arguments':{ 'id': 'iothread1' } }
> > +{'execute': 'object-del', 'arguments':{ 'id': 'm0' } }
> > +{'execute': 'object-del', 'arguments':{ 'id': 'redire0' } }
> > +{'execute': 'object-del', 'arguments':{ 'id': 'redire1' } }
> > +{'execute': 'x-colo-lost-heartbeat' }
> > +
> > +== Secondary Failover ==
> > +The Primary died, resume on the Secondary and prepare to become the
> > new
> > +Primary
> > +
> > +{'execute': 'nbd-server-stop'}
> > +{'execute': 'x-colo-lost-heartbeat'}
> > +
> > +{'execute': 'object-del', 'arguments':{ 'id': 'f2' } }
> > +{'execute': 'object-del', 'arguments':{ 'id': 'f1' } }
> > +{'execute': 'chardev-remove', 'arguments':{ 'id': 'red1' } }
> > +{'execute': 'chardev-remove', 'arguments':{ 'id': 'red0' } }
> > +
> > +{'execute': 'chardev-add', 'arguments':{ 'id': 'mirror0', 'backend':
> > +{'type': 'socket', 'data': {'addr': { 'type': 'inet', 'data': { 'host':
> > +'0.0.0.0', 'port': '9003' } }, 'server': true } } } }  
> 
> Same like I said before.
> 
> Others statement looks good for me.
> 
> Thanks
> Zhang Chen
> 
> > +{'execute': 'chardev-add', 'arguments':{ 'id': 'compare1', 'backend':
> > +{'type': 'socket', 'data': {'addr': { 'type': 'inet', 'data': { 'host':
> > +'0.0.0.0', 'port': '9004' } }, 'server': true } } } }
> > +{'execute': 'chardev-add', 'arguments':{ 'id': 'compare0', 'backend':
> > +{'type': 'socket', 'data': {'addr': { 'type': 'inet', 'data': { 'host':
> > +'127.0.0.1', 'port': '9001' } }, 'server': true } } } }
> > +{'execute': 'chardev-add', 'arguments':{ 'id': 'compare0-0', 'backend':
> > +{'type': 'socket', 'data': {'addr': { 'type': 'inet', 'data': { 'host':
> > +'127.0.0.1', 'port': '9001' } }, 'server': false } } } }
> > +{'execute': 'chardev-add', 'arguments':{ 'id': 'compare_out',
> > +'backend': {'type': 'socket', 'data': {'addr': { 'type': 'inet',
> > +'data': { 'host': '127.0.0.1', 'port': '9005' } }, 'server': true } } }
> > +}
> > +{'execute': 'chardev-add', 'arguments':{ 'id': 'compare_out0',
> > +'backend': {'type': 'socket', 'data': {'addr': { 'type': 'inet',
> > +'data': { 'host': '127.0.0.1', 'port': '9005' } }, 'server': false } }
> > +} }
> > +
> > +== Primary resume replication ==
> > +Resume replication after new Secondary is up.
> > +
> > +Start the new Secondary (Steps 2 and 3 above), then on the Primary:
> > +{'execute': 'drive-mirror', 'arguments':{ 'device': 'colo-disk0',
> > +'job-id': 'resync', 'target': 'nbd://127.0.0.2:9999/parent0', 'mode':
> > +'existing', 'format': 'raw', 'sync': 'full'} }
> > +
> > +Wait until disk is synced, then:
> > +{'execute': 'stop'}
> > +{'execute': 'block-job-cancel', 'arguments':{ 'device': 'resync'} }
> > +
> > +{'execute': 'human-monitor-command', 'arguments':{ 'command-line':
> > +'drive_add -n buddy
> > +driver=replication,mode=primary,file.driver=nbd,file.host=127.0.0.2,fil
> > +e.port=9999,file.export=parent0,node-name=replication0'}}
> > +{'execute': 'x-blockdev-change', 'arguments':{ 'parent': 'colo-disk0',
> > +'node': 'replication0' } }
> > +
> > +{'execute': 'object-add', 'arguments':{ 'qom-type': 'filter-mirror',
> > +'id': 'm0', 'props': { 'netdev': 'hn0', 'queue': 'tx', 'outdev':
> > +'mirror0' } } }
> > +{'execute': 'object-add', 'arguments':{ 'qom-type':
> > +'filter-redirector', 'id': 'redire0', 'props': { 'netdev': 'hn0',
> > +'queue': 'rx', 'indev': 'compare_out' } } }
> > +{'execute': 'object-add', 'arguments':{ 'qom-type':
> > +'filter-redirector', 'id': 'redire1', 'props': { 'netdev': 'hn0',
> > +'queue': 'rx', 'outdev': 'compare0' } } }
> > +{'execute': 'object-add', 'arguments':{ 'qom-type': 'iothread', 'id':
> > +'iothread1' } }
> > +{'execute': 'object-add', 'arguments':{ 'qom-type': 'colo-compare',
> > +'id': 'comp0', 'props': { 'primary_in': 'compare0-0', 'secondary_in':
> > +'compare1', 'outdev': 'compare_out0', 'iothread': 'iothread1' } } }
> > +
> > +{'execute': 'migrate-set-capabilities', 'arguments':{ 'capabilities': [
> > +{'capability': 'x-colo', 'state': true } ] } }
> > +{'execute': 'migrate', 'arguments':{ 'uri': 'tcp:127.0.0.2:9998' } }
> > +
> > +Note:
> > +If this Primary previously was a Secondary, then we need to insert the
> > +filters before the filter-rewriter by using the
> > +"'insert': 'before', 'position': 'id=rew0'" Options. See below.
> > +
> > +== Secondary resume replication ==
> > +Become Primary and resume replication after new Secondary is up. Note
> > +that now 127.0.0.1 is the Secondary and 127.0.0.2 is the Primary.
> > +
> > +Start the new Secondary (Steps 2 and 3 above, but with
> > +primary_ip=127.0.0.2), then on the old Secondary:
> > +{'execute': 'drive-mirror', 'arguments':{ 'device': 'colo-disk0',
> > +'job-id': 'resync', 'target': 'nbd://127.0.0.1:9999/parent0', 'mode':
> > +'existing', 'format': 'raw', 'sync': 'full'} }
> > +
> > +Wait until disk is synced, then:
> > +{'execute': 'stop'}
> > +{'execute': 'block-job-cancel', 'arguments':{ 'device': 'resync' } }
> > 
> > -5. Failover test
> > -You can kill Primary VM and run 'x_colo_lost_heartbeat' in Secondary VM's -
> > monitor at the same time, then SVM will failover and client will not detect
> > this -change.
> > +{'execute': 'human-monitor-command', 'arguments':{ 'command-line':
> > +'drive_add -n buddy
> > +driver=replication,mode=primary,file.driver=nbd,file.host=127.0.0.1,fil
> > +e.port=9999,file.export=parent0,node-name=replication0'}}
> > +{'execute': 'x-blockdev-change', 'arguments':{ 'parent': 'colo-disk0',
> > +'node': 'replication0' } }
> > 
> > -Before issuing '{ "execute": "x-colo-lost-heartbeat" }' command, we have to
> > -issue block related command to stop block replication.
> > -Primary:
> > -  Remove the nbd child from the quorum:
> > -  { 'execute': 'x-blockdev-change', 'arguments': {'parent': 'colo-disk0', 'child':
> > 'children.1'}}
> > -  { 'execute': 'human-monitor-command','arguments': {'command-line':
> > 'drive_del blk-buddy0'}}
> > -  Note: there is no qmp command to remove the blockdev now
> > +{'execute': 'object-add', 'arguments':{ 'qom-type': 'filter-mirror',
> > +'id': 'm0', 'props': { 'insert': 'before', 'position': 'id=rew0',
> > +'netdev': 'hn0', 'queue': 'tx', 'outdev': 'mirror0' } } }
> > +{'execute': 'object-add', 'arguments':{ 'qom-type':
> > +'filter-redirector', 'id': 'redire0', 'props': { 'insert': 'before',
> > +'position': 'id=rew0', 'netdev': 'hn0', 'queue': 'rx', 'indev':
> > +'compare_out' } } }
> > +{'execute': 'object-add', 'arguments':{ 'qom-type':
> > +'filter-redirector', 'id': 'redire1', 'props': { 'insert': 'before',
> > +'position': 'id=rew0', 'netdev': 'hn0', 'queue': 'rx', 'outdev':
> > +'compare0' } } }
> > +{'execute': 'object-add', 'arguments':{ 'qom-type': 'iothread', 'id':
> > +'iothread1' } }
> > +{'execute': 'object-add', 'arguments':{ 'qom-type': 'colo-compare',
> > +'id': 'comp0', 'props': { 'primary_in': 'compare0-0', 'secondary_in':
> > +'compare1', 'outdev': 'compare_out0', 'iothread': 'iothread1' } } }
> > 
> > -Secondary:
> > -  The primary host is down, so we should do the following thing:
> > -  { 'execute': 'nbd-server-stop' }
> > +{'execute': 'migrate-set-capabilities', 'arguments':{ 'capabilities': [
> > +{'capability': 'x-colo', 'state': true } ] } }
> > +{'execute': 'migrate', 'arguments':{ 'uri': 'tcp:127.0.0.1:9998' } }
> > 
> >  == TODO ==
> > -1. Support continuous VM replication.
> > -2. Support shared storage.
> > -3. Develop the heartbeat part.
> > -4. Reduce checkpoint VM’s downtime while doing checkpoint.
> > +1. Support shared storage.
> > +2. Develop the heartbeat part.
> > +3. Reduce checkpoint VM’s downtime while doing checkpoint.

Zhang Chen Oct. 10, 2019, 10:34 a.m. UTC | #3

> -----Original Message-----
> From: Lukas Straub <[e-mail]>
> Sent: Wednesday, October 9, 2019 11:17 PM
> To: Zhang, Chen <[e-mail]>
> Cc: qemu-devel <[e-mail]>; Jason Wang
> <[e-mail]>; Wen Congyang <[e-mail]>;
> Xie Changlong <[e-mail]>; Kevin Wolf
> <[e-mail]>; Max Reitz <[e-mail]>; qemu-block
> <[e-mail]>
> Subject: Re: [PATCH v6 4/4] colo: Update Documentation for continuous
> replication
> 
> On Wed, 9 Oct 2019 08:36:52 +0000
> "Zhang, Chen" <[e-mail]> wrote:
> 
> > > -----Original Message-----
> > > From: Lukas Straub <[e-mail]>
> > > Sent: Saturday, October 5, 2019 9:06 PM
> > > To: qemu-devel <[e-mail]>
> > > Cc: Zhang, Chen <[e-mail]>; Jason Wang
> > > <[e-mail]>; Wen Congyang
> <[e-mail]>; Xie
> > > Changlong <[e-mail]>; Kevin Wolf
> <[e-mail]>;
> > > Max Reitz <[e-mail]>; qemu-block <qemu-
> [e-mail]>
> > > Subject: [PATCH v6 4/4] colo: Update Documentation for continuous
> > > replication
> > >
> > > Document the qemu command-line and qmp commands for continuous
> > > replication
> > >
> > > Signed-off-by: Lukas Straub <[e-mail]>
> > > ---
> > >  docs/COLO-FT.txt           | 213 +++++++++++++++++++++++++++----------
> > >  docs/block-replication.txt |  28 +++--
> > >  2 files changed, 174 insertions(+), 67 deletions(-)
> > >
> > > diff --git a/docs/COLO-FT.txt b/docs/COLO-FT.txt index
> > > ad24680d13..bc1a0ccb99 100644
> > > --- a/docs/COLO-FT.txt
> > > +++ b/docs/COLO-FT.txt
> > > @@ -145,35 +145,65 @@ The diagram just shows the main qmp
> command,
> > > you can get the detail  in test procedure.
> > >
> > > ...
> > >
> > > +Note: Here we are running both instances on the same Host for
> > > +testing, change the IP Addresses if you want to run it on two
> > > +Hosts. Initally
> > > +127.0.0.1 is the Primary Host and 127.0.0.2 is the Secondary Host.
> > > +
> > > +== Startup qemu ==
> > > +1. Primary:
> > > +Note: Initally, $imagefolder/primary.qcow2 needs to be copied to all
> Hosts.
> > > +# imagefolder="/mnt/vms/colo-test-primary"
> > > +
> > > +# qemu-system-x86_64 -enable-kvm -cpu qemu64,+kvmclock -m 512 -
> smp
> > > 1 -qmp stdio \
> > > +   -device piix3-usb-uhci -device usb-tablet -name primary \
> > > +   -netdev
> > > + tap,id=hn0,vhost=off,helper=/usr/lib/qemu/qemu-bridge-helper
> > > \
> > > +   -device rtl8139,id=e0,netdev=hn0 \
> > > +   -chardev socket,id=mirror0,host=0.0.0.0,port=9003,server,nowait \
> > > +   -chardev socket,id=compare1,host=0.0.0.0,port=9004,server,wait \
> >
> > We should change the host=127.0.0.1 consistent with the expression below.
> 
> Hi,
> This (and the IPs below in the QMP commands) needs to be this way,
> because it's a listening port and with 127.0.0.1 it would only listen on the
> loopback ip and wouldn't be reachable from another node for example. With
> 0.0.0.0 it will listen on all Interfaces.

Yes, I know.  For this command demo, maybe use 192.168.0.1/192.168.0.2 are more clear.

> 
> > > +   -chardev socket,id=compare0,host=127.0.0.1,port=9001,server,nowait
> \
> > > +   -chardev socket,id=compare0-0,host=127.0.0.1,port=9001 \
> > > +   -chardev
> > > + socket,id=compare_out,host=127.0.0.1,port=9005,server,nowait
> > > \
> > > +   -chardev socket,id=compare_out0,host=127.0.0.1,port=9005 \
> > > +   -object filter-mirror,id=m0,netdev=hn0,queue=tx,outdev=mirror0 \
> > > +   -object filter-
> > > redirector,netdev=hn0,id=redire0,queue=rx,indev=compare_out \
> > > +   -object filter-
> > > redirector,netdev=hn0,id=redire1,queue=rx,outdev=compare0 \
> > > +   -object iothread,id=iothread1 \
> > > +   -object
> > > +colo-compare,id=comp0,primary_in=compare0-
> > > 0,secondary_in=compare1,\
> > > +outdev=compare_out0,iothread=iothread1 \
> > > +   -drive
> > > +if=ide,id=colo-disk0,driver=quorum,read-pattern=fifo,vote-threshold
> > > +=1,\
> > > +children.0.file.filename=$imagefolder/primary.qcow2,children.0.driv
> > > +er=q
> > > +cow2 -S
> > > +
> > > +2. Secondary:
> > > +# imagefolder="/mnt/vms/colo-test-secondary"
> > > +# primary_ip=127.0.0.1
> > > +
> > > +# qemu-img create -f qcow2 $imagefolder/secondary-active.qcow2 10G
> > > +
> > > +# qemu-img create -f qcow2 $imagefolder/secondary-hidden.qcow2
> 10G
> > > +
> >
> > The active disk and hidden disk just need create one time, we can note that
> here.
> 
> Ok, I will Note that. But I will wait until the block changes are reviewed
> before sending the next version.

That's fine for me.

Thanks
Zhang Chen

> 
> Regards,
> Lukas Straub
> 
> > > +# qemu-system-x86_64 -enable-kvm -cpu qemu64,+kvmclock -m 512 -
> smp
> > > 1 -qmp stdio \
> > > +   -device piix3-usb-uhci -device usb-tablet -name secondary \
> > > +   -netdev
> > > + tap,id=hn0,vhost=off,helper=/usr/lib/qemu/qemu-bridge-helper
> > > \
> > > +   -device rtl8139,id=e0,netdev=hn0 \
> > > +   -chardev socket,id=red0,host=$primary_ip,port=9003,reconnect=1 \
> > > +   -chardev socket,id=red1,host=$primary_ip,port=9004,reconnect=1 \
> > > +   -object filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0 \
> > > +   -object filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1 \
> > > +   -object filter-rewriter,id=rew0,netdev=hn0,queue=all \
> > > +   -drive
> > > if=none,id=parent0,file.filename=$imagefolder/primary.qcow2,driver=q
> > > cow
> > > 2 \
> > > +   -drive
> > > +if=none,id=childs0,driver=replication,mode=secondary,file.driver=qc
> > > +ow2,
> > > +\
> > > +top-id=childs0,file.file.filename=$imagefolder/secondary-active.qco
> > > +w2,\
> > > +file.backing.driver=qcow2,file.backing.file.filename=$imagefolder/s
> > > +econ
> > > +dary-hidden.qcow2,\
> > > +file.backing.backing=parent0 \
> > > +   -drive
> > > +if=ide,id=colo-disk0,driver=quorum,read-pattern=fifo,vote-threshold
> > > +=1,\
> > > +children.0=childs0 \
> > > +   -incoming tcp:0.0.0.0:9998
> > > +
> > > +
> > > +3. On Secondary VM's QEMU monitor, issue command
> > >  {'execute':'qmp_capabilities'}
> > > -{ 'execute': 'nbd-server-start',
> > > -  'arguments': {'addr': {'type': 'inet', 'data': {'host': 'xx.xx.xx.xx', 'port':
> > > '8889'} } } -}
> > > -{'execute': 'nbd-server-add', 'arguments': {'device':
> > > 'secondary-disk0',
> > > 'writable': true } }
> > > +{'execute': 'nbd-server-start', 'arguments': {'addr': {'type':
> > > +'inet',
> > > +'data': {'host': '0.0.0.0', 'port': '9999'} } } }
> > > +{'execute': 'nbd-server-add', 'arguments': {'device': 'parent0',
> > > +'writable': true } }
> > >
> > >  Note:
> > >    a. The qmp command nbd-server-start and nbd-server-add must be
> > > run @@ -182,44 +212,113 @@ Note:
> > >       same.
> > >    c. It is better to put active disk and hidden disk in ramdisk.
> > >
> > > -3. On Primary VM's QEMU monitor, issue command:
> > > +4. On Primary VM's QEMU monitor, issue command:
> > >  {'execute':'qmp_capabilities'}
> > > -{ 'execute': 'human-monitor-command',
> > > -  'arguments': {'command-line': 'drive_add -n buddy
> > > driver=replication,mode=primary,file.driver=nbd,file.host=xx.xx.xx.x
> > > x,file.p
> > > ort=8889,file.export=secondary-disk0,node-name=nbd_client0'}}
> > > -{ 'execute':'x-blockdev-change', 'arguments':{'parent':
> > > 'primary-disk0',
> > > 'node': 'nbd_client0' } } -{ 'execute': 'migrate-set-capabilities',
> > > -      'arguments': {'capabilities': [ {'capability': 'x-colo', 'state': true } ] } }
> > > -{ 'execute': 'migrate', 'arguments': {'uri': 'tcp:xx.xx.xx.xx:8888'
> > > } }
> > > +{'execute': 'human-monitor-command', 'arguments': {'command-line':
> > > +'drive_add -n buddy
> > > +driver=replication,mode=primary,file.driver=nbd,file.host=127.0.0.2
> > > +,fil e.port=9999,file.export=parent0,node-name=replication0'}}
> > > +{'execute': 'x-blockdev-change', 'arguments':{'parent':
> > > +'colo-disk0',
> > > +'node': 'replication0' } }
> > > +{'execute': 'migrate-set-capabilities', 'arguments':
> > > +{'capabilities': [
> > > +{'capability': 'x-colo', 'state': true } ] } }
> > > +{'execute': 'migrate', 'arguments': {'uri': 'tcp:127.0.0.2:9998' }
> > > +}
> > >
> > >    Note:
> > >    a. There should be only one NBD Client for each primary disk.
> > > -  b. xx.xx.xx.xx is the secondary physical machine's hostname or IP
> > > -  c. The qmp command line must be run after running qmp command
> > > line in
> > > +  b. The qmp command line must be run after running qmp command
> > > + line in
> > >       secondary qemu.
> > >
> > > -4. After the above steps, you will see, whenever you make changes
> > > to PVM, SVM will be synced.
> > > +5. After the above steps, you will see, whenever you make changes
> > > +to PVM,
> > > SVM will be synced.
> > >  You can issue command '{ "execute": "migrate-set-parameters" ,
> > > "arguments":{ "x-checkpoint-delay": 2000 } }'
> > > -to change the checkpoint period time
> > > +to change the idle checkpoint period time
> > > +
> > > +6. Failover test
> > > +You can kill one of the VMs and Failover on the surviving VM:
> > > +
> > > +If you killed the Secondary, then follow "Primary Failover". After
> > > +that, if you want to resume the replication, follow "Primary resume
> > > replication"
> > > +
> > > +If you killed the Primary, then follow "Secondary Failover". After
> > > +that, if you want to resume the replication, follow "Secondary
> > > +resume
> > > replication"
> > > +
> > > +== Primary Failover ==
> > > +The Secondary died, resume on the Primary
> > > +
> > > +{'execute': 'x-blockdev-change', 'arguments':{ 'parent':
> > > +'colo-disk0',
> > > +'child': 'children.1'} }
> > > +{'execute': 'human-monitor-command', 'arguments':{ 'command-line':
> > > +'drive_del replication0' } }
> > > +{'execute': 'object-del', 'arguments':{ 'id': 'comp0' } }
> > > +{'execute': 'object-del', 'arguments':{ 'id': 'iothread1' } }
> > > +{'execute': 'object-del', 'arguments':{ 'id': 'm0' } }
> > > +{'execute': 'object-del', 'arguments':{ 'id': 'redire0' } }
> > > +{'execute': 'object-del', 'arguments':{ 'id': 'redire1' } }
> > > +{'execute': 'x-colo-lost-heartbeat' }
> > > +
> > > +== Secondary Failover ==
> > > +The Primary died, resume on the Secondary and prepare to become the
> > > new
> > > +Primary
> > > +
> > > +{'execute': 'nbd-server-stop'}
> > > +{'execute': 'x-colo-lost-heartbeat'}
> > > +
> > > +{'execute': 'object-del', 'arguments':{ 'id': 'f2' } }
> > > +{'execute': 'object-del', 'arguments':{ 'id': 'f1' } }
> > > +{'execute': 'chardev-remove', 'arguments':{ 'id': 'red1' } }
> > > +{'execute': 'chardev-remove', 'arguments':{ 'id': 'red0' } }
> > > +
> > > +{'execute': 'chardev-add', 'arguments':{ 'id': 'mirror0', 'backend':
> > > +{'type': 'socket', 'data': {'addr': { 'type': 'inet', 'data': { 'host':
> > > +'0.0.0.0', 'port': '9003' } }, 'server': true } } } }
> >
> > Same like I said before.
> >
> > Others statement looks good for me.
> >
> > Thanks
> > Zhang Chen
> >
> > > +{'execute': 'chardev-add', 'arguments':{ 'id': 'compare1', 'backend':
> > > +{'type': 'socket', 'data': {'addr': { 'type': 'inet', 'data': { 'host':
> > > +'0.0.0.0', 'port': '9004' } }, 'server': true } } } }
> > > +{'execute': 'chardev-add', 'arguments':{ 'id': 'compare0', 'backend':
> > > +{'type': 'socket', 'data': {'addr': { 'type': 'inet', 'data': { 'host':
> > > +'127.0.0.1', 'port': '9001' } }, 'server': true } } } }
> > > +{'execute': 'chardev-add', 'arguments':{ 'id': 'compare0-0', 'backend':
> > > +{'type': 'socket', 'data': {'addr': { 'type': 'inet', 'data': { 'host':
> > > +'127.0.0.1', 'port': '9001' } }, 'server': false } } } }
> > > +{'execute': 'chardev-add', 'arguments':{ 'id': 'compare_out',
> > > +'backend': {'type': 'socket', 'data': {'addr': { 'type': 'inet',
> > > +'data': { 'host': '127.0.0.1', 'port': '9005' } }, 'server': true }
> > > +} } }
> > > +{'execute': 'chardev-add', 'arguments':{ 'id': 'compare_out0',
> > > +'backend': {'type': 'socket', 'data': {'addr': { 'type': 'inet',
> > > +'data': { 'host': '127.0.0.1', 'port': '9005' } }, 'server': false
> > > +} } } }
> > > +
> > > +== Primary resume replication ==
> > > +Resume replication after new Secondary is up.
> > > +
> > > +Start the new Secondary (Steps 2 and 3 above), then on the Primary:
> > > +{'execute': 'drive-mirror', 'arguments':{ 'device': 'colo-disk0',
> > > +'job-id': 'resync', 'target': 'nbd://127.0.0.2:9999/parent0', 'mode':
> > > +'existing', 'format': 'raw', 'sync': 'full'} }
> > > +
> > > +Wait until disk is synced, then:
> > > +{'execute': 'stop'}
> > > +{'execute': 'block-job-cancel', 'arguments':{ 'device': 'resync'} }
> > > +
> > > +{'execute': 'human-monitor-command', 'arguments':{ 'command-line':
> > > +'drive_add -n buddy
> > > +driver=replication,mode=primary,file.driver=nbd,file.host=127.0.0.2
> > > +,fil e.port=9999,file.export=parent0,node-name=replication0'}}
> > > +{'execute': 'x-blockdev-change', 'arguments':{ 'parent':
> > > +'colo-disk0',
> > > +'node': 'replication0' } }
> > > +
> > > +{'execute': 'object-add', 'arguments':{ 'qom-type':
> > > +'filter-mirror',
> > > +'id': 'm0', 'props': { 'netdev': 'hn0', 'queue': 'tx', 'outdev':
> > > +'mirror0' } } }
> > > +{'execute': 'object-add', 'arguments':{ 'qom-type':
> > > +'filter-redirector', 'id': 'redire0', 'props': { 'netdev': 'hn0',
> > > +'queue': 'rx', 'indev': 'compare_out' } } }
> > > +{'execute': 'object-add', 'arguments':{ 'qom-type':
> > > +'filter-redirector', 'id': 'redire1', 'props': { 'netdev': 'hn0',
> > > +'queue': 'rx', 'outdev': 'compare0' } } }
> > > +{'execute': 'object-add', 'arguments':{ 'qom-type': 'iothread', 'id':
> > > +'iothread1' } }
> > > +{'execute': 'object-add', 'arguments':{ 'qom-type': 'colo-compare',
> > > +'id': 'comp0', 'props': { 'primary_in': 'compare0-0', 'secondary_in':
> > > +'compare1', 'outdev': 'compare_out0', 'iothread': 'iothread1' } } }
> > > +
> > > +{'execute': 'migrate-set-capabilities', 'arguments':{
> > > +'capabilities': [
> > > +{'capability': 'x-colo', 'state': true } ] } }
> > > +{'execute': 'migrate', 'arguments':{ 'uri': 'tcp:127.0.0.2:9998' }
> > > +}
> > > +
> > > +Note:
> > > +If this Primary previously was a Secondary, then we need to insert
> > > +the filters before the filter-rewriter by using the
> > > +"'insert': 'before', 'position': 'id=rew0'" Options. See below.
> > > +
> > > +== Secondary resume replication ==
> > > +Become Primary and resume replication after new Secondary is up.
> > > +Note that now 127.0.0.1 is the Secondary and 127.0.0.2 is the Primary.
> > > +
> > > +Start the new Secondary (Steps 2 and 3 above, but with
> > > +primary_ip=127.0.0.2), then on the old Secondary:
> > > +{'execute': 'drive-mirror', 'arguments':{ 'device': 'colo-disk0',
> > > +'job-id': 'resync', 'target': 'nbd://127.0.0.1:9999/parent0', 'mode':
> > > +'existing', 'format': 'raw', 'sync': 'full'} }
> > > +
> > > +Wait until disk is synced, then:
> > > +{'execute': 'stop'}
> > > +{'execute': 'block-job-cancel', 'arguments':{ 'device': 'resync' }
> > > +}
> > >
> > > -5. Failover test
> > > -You can kill Primary VM and run 'x_colo_lost_heartbeat' in
> > > Secondary VM's - monitor at the same time, then SVM will failover
> > > and client will not detect this -change.
> > > +{'execute': 'human-monitor-command', 'arguments':{ 'command-line':
> > > +'drive_add -n buddy
> > > +driver=replication,mode=primary,file.driver=nbd,file.host=127.0.0.1
> > > +,fil e.port=9999,file.export=parent0,node-name=replication0'}}
> > > +{'execute': 'x-blockdev-change', 'arguments':{ 'parent':
> > > +'colo-disk0',
> > > +'node': 'replication0' } }
> > >
> > > -Before issuing '{ "execute": "x-colo-lost-heartbeat" }' command, we
> > > have to -issue block related command to stop block replication.
> > > -Primary:
> > > -  Remove the nbd child from the quorum:
> > > -  { 'execute': 'x-blockdev-change', 'arguments': {'parent': 'colo-disk0',
> 'child':
> > > 'children.1'}}
> > > -  { 'execute': 'human-monitor-command','arguments': {'command-line':
> > > 'drive_del blk-buddy0'}}
> > > -  Note: there is no qmp command to remove the blockdev now
> > > +{'execute': 'object-add', 'arguments':{ 'qom-type':
> > > +'filter-mirror',
> > > +'id': 'm0', 'props': { 'insert': 'before', 'position': 'id=rew0',
> > > +'netdev': 'hn0', 'queue': 'tx', 'outdev': 'mirror0' } } }
> > > +{'execute': 'object-add', 'arguments':{ 'qom-type':
> > > +'filter-redirector', 'id': 'redire0', 'props': { 'insert':
> > > +'before',
> > > +'position': 'id=rew0', 'netdev': 'hn0', 'queue': 'rx', 'indev':
> > > +'compare_out' } } }
> > > +{'execute': 'object-add', 'arguments':{ 'qom-type':
> > > +'filter-redirector', 'id': 'redire1', 'props': { 'insert':
> > > +'before',
> > > +'position': 'id=rew0', 'netdev': 'hn0', 'queue': 'rx', 'outdev':
> > > +'compare0' } } }
> > > +{'execute': 'object-add', 'arguments':{ 'qom-type': 'iothread', 'id':
> > > +'iothread1' } }
> > > +{'execute': 'object-add', 'arguments':{ 'qom-type': 'colo-compare',
> > > +'id': 'comp0', 'props': { 'primary_in': 'compare0-0', 'secondary_in':
> > > +'compare1', 'outdev': 'compare_out0', 'iothread': 'iothread1' } } }
> > >
> > > -Secondary:
> > > -  The primary host is down, so we should do the following thing:
> > > -  { 'execute': 'nbd-server-stop' }
> > > +{'execute': 'migrate-set-capabilities', 'arguments':{
> > > +'capabilities': [
> > > +{'capability': 'x-colo', 'state': true } ] } }
> > > +{'execute': 'migrate', 'arguments':{ 'uri': 'tcp:127.0.0.1:9998' }
> > > +}
> > >
> > >  == TODO ==
> > > -1. Support continuous VM replication.
> > > -2. Support shared storage.
> > > -3. Develop the heartbeat part.
> > > -4. Reduce checkpoint VM’s downtime while doing checkpoint.
> > > +1. Support shared storage.
> > > +2. Develop the heartbeat part.
> > > +3. Reduce checkpoint VM’s downtime while doing checkpoint.

Lukas Straub Oct. 11, 2019, 4 p.m. UTC | #4

On Thu, 10 Oct 2019 10:34:15 +0000
"Zhang, Chen" <[e-mail]> wrote:

> > -----Original Message-----
> > From: Lukas Straub <[e-mail]>
> > Sent: Wednesday, October 9, 2019 11:17 PM
> > To: Zhang, Chen <[e-mail]>
> > Cc: qemu-devel <[e-mail]>; Jason Wang
> > <[e-mail]>; Wen Congyang <[e-mail]>;
> > Xie Changlong <[e-mail]>; Kevin Wolf
> > <[e-mail]>; Max Reitz <[e-mail]>; qemu-block
> > <[e-mail]>
> > Subject: Re: [PATCH v6 4/4] colo: Update Documentation for continuous
> > replication
> > 
> > On Wed, 9 Oct 2019 08:36:52 +0000
> > "Zhang, Chen" <[e-mail]> wrote:
> >   
> > > > -----Original Message-----
> > > > From: Lukas Straub <[e-mail]>
> > > > Sent: Saturday, October 5, 2019 9:06 PM
> > > > To: qemu-devel <[e-mail]>
> > > > Cc: Zhang, Chen <[e-mail]>; Jason Wang
> > > > <[e-mail]>; Wen Congyang  
> > <[e-mail]>; Xie  
> > > > Changlong <[e-mail]>; Kevin Wolf  
> > <[e-mail]>;  
> > > > Max Reitz <[e-mail]>; qemu-block <qemu-  
> > [e-mail]>  
> > > > Subject: [PATCH v6 4/4] colo: Update Documentation for continuous
> > > > replication
> > > >
> > > > Document the qemu command-line and qmp commands for continuous
> > > > replication
> > > >
> > > > Signed-off-by: Lukas Straub <[e-mail]>
> > > > ---
> > > >  docs/COLO-FT.txt           | 213 +++++++++++++++++++++++++++----------
> > > >  docs/block-replication.txt |  28 +++--
> > > >  2 files changed, 174 insertions(+), 67 deletions(-)
> > > >
> > > > diff --git a/docs/COLO-FT.txt b/docs/COLO-FT.txt index
> > > > ad24680d13..bc1a0ccb99 100644
> > > > --- a/docs/COLO-FT.txt
> > > > +++ b/docs/COLO-FT.txt
> > > > @@ -145,35 +145,65 @@ The diagram just shows the main qmp  
> > command,  
> > > > you can get the detail  in test procedure.
> > > >
> > > > ...
> > > >
> > > > +Note: Here we are running both instances on the same Host for
> > > > +testing, change the IP Addresses if you want to run it on two
> > > > +Hosts. Initally
> > > > +127.0.0.1 is the Primary Host and 127.0.0.2 is the Secondary Host.
> > > > +
> > > > +== Startup qemu ==
> > > > +1. Primary:
> > > > +Note: Initally, $imagefolder/primary.qcow2 needs to be copied to all  
> > Hosts.  
> > > > +# imagefolder="/mnt/vms/colo-test-primary"
> > > > +
> > > > +# qemu-system-x86_64 -enable-kvm -cpu qemu64,+kvmclock -m 512 -  
> > smp  
> > > > 1 -qmp stdio \
> > > > +   -device piix3-usb-uhci -device usb-tablet -name primary \
> > > > +   -netdev
> > > > + tap,id=hn0,vhost=off,helper=/usr/lib/qemu/qemu-bridge-helper
> > > > \
> > > > +   -device rtl8139,id=e0,netdev=hn0 \
> > > > +   -chardev socket,id=mirror0,host=0.0.0.0,port=9003,server,nowait \
> > > > +   -chardev socket,id=compare1,host=0.0.0.0,port=9004,server,wait \  
> > >
> > > We should change the host=127.0.0.1 consistent with the expression below.  
> > 
> > Hi,
> > This (and the IPs below in the QMP commands) needs to be this way,
> > because it's a listening port and with 127.0.0.1 it would only listen on the
> > loopback ip and wouldn't be reachable from another node for example. With
> > 0.0.0.0 it will listen on all Interfaces.  
> 
> Yes, I know.  For this command demo, maybe use 192.168.0.1/192.168.0.2 are more clear.

Hmm,
the compare0 and compare_out actually can be replaced by unix sockets. 
So what do you think about the following?

   -chardev socket,id=mirror0,host=127.0.0.1,port=9003,server,nowait \
   -chardev socket,id=compare1,host=127.0.0.1,port=9004,server,wait \
   -chardev socket,id=compare0,path=/tmp/compare0.sock,server,nowait \
   -chardev socket,id=compare0-0,path=/tmp/compare0.sock \
   -chardev socket,id=compare_out,path=/tmp/compare_out.sock,server,nowait \
   -chardev socket,id=compare_out0,path=/tmp/compare_out.sock \

> >   
> > > > +   -chardev socket,id=compare0,host=127.0.0.1,port=9001,server,nowait  
> > \  
> > > > +   -chardev socket,id=compare0-0,host=127.0.0.1,port=9001 \
> > > > +   -chardev
> > > > + socket,id=compare_out,host=127.0.0.1,port=9005,server,nowait
> > > > \
> > > > +   -chardev socket,id=compare_out0,host=127.0.0.1,port=9005 \
> > > > +   -object filter-mirror,id=m0,netdev=hn0,queue=tx,outdev=mirror0 \
> > > > +   -object filter-
> > > > redirector,netdev=hn0,id=redire0,queue=rx,indev=compare_out \
> > > > +   -object filter-
> > > > redirector,netdev=hn0,id=redire1,queue=rx,outdev=compare0 \
> > > > +   -object iothread,id=iothread1 \
> > > > +   -object
> > > > +colo-compare,id=comp0,primary_in=compare0-
> > > > 0,secondary_in=compare1,\
> > > > +outdev=compare_out0,iothread=iothread1 \
> > > > +   -drive
> > > > +if=ide,id=colo-disk0,driver=quorum,read-pattern=fifo,vote-threshold
> > > > +=1,\
> > > > +children.0.file.filename=$imagefolder/primary.qcow2,children.0.driv
> > > > +er=q
> > > > +cow2 -S
> > > > +
> > > > +2. Secondary:
> > > > +# imagefolder="/mnt/vms/colo-test-secondary"
> > > > +# primary_ip=127.0.0.1
> > > > +
> > > > +# qemu-img create -f qcow2 $imagefolder/secondary-active.qcow2 10G
> > > > +
> > > > +# qemu-img create -f qcow2 $imagefolder/secondary-hidden.qcow2  
> > 10G  
> > > > +  
> > >
> > > The active disk and hidden disk just need create one time, we can note that  
> > here.
> > 
> > Ok, I will Note that. But I will wait until the block changes are reviewed
> > before sending the next version.  
> 
> That's fine for me.
> 
> Thanks
> Zhang Chen
> 
> > 
> > Regards,
> > Lukas Straub
> >   
> > > > +# qemu-system-x86_64 -enable-kvm -cpu qemu64,+kvmclock -m 512 -  
> > smp  
> > > > 1 -qmp stdio \
> > > > +   -device piix3-usb-uhci -device usb-tablet -name secondary \
> > > > +   -netdev
> > > > + tap,id=hn0,vhost=off,helper=/usr/lib/qemu/qemu-bridge-helper
> > > > \
> > > > +   -device rtl8139,id=e0,netdev=hn0 \
> > > > +   -chardev socket,id=red0,host=$primary_ip,port=9003,reconnect=1 \
> > > > +   -chardev socket,id=red1,host=$primary_ip,port=9004,reconnect=1 \
> > > > +   -object filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0 \
> > > > +   -object filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1 \
> > > > +   -object filter-rewriter,id=rew0,netdev=hn0,queue=all \
> > > > +   -drive
> > > > if=none,id=parent0,file.filename=$imagefolder/primary.qcow2,driver=q
> > > > cow
> > > > 2 \
> > > > +   -drive
> > > > +if=none,id=childs0,driver=replication,mode=secondary,file.driver=qc
> > > > +ow2,
> > > > +\
> > > > +top-id=childs0,file.file.filename=$imagefolder/secondary-active.qco
> > > > +w2,\
> > > > +file.backing.driver=qcow2,file.backing.file.filename=$imagefolder/s
> > > > +econ
> > > > +dary-hidden.qcow2,\
> > > > +file.backing.backing=parent0 \
> > > > +   -drive
> > > > +if=ide,id=colo-disk0,driver=quorum,read-pattern=fifo,vote-threshold
> > > > +=1,\
> > > > +children.0=childs0 \
> > > > +   -incoming tcp:0.0.0.0:9998
> > > > +
> > > > +
> > > > +3. On Secondary VM's QEMU monitor, issue command
> > > >  {'execute':'qmp_capabilities'}
> > > > -{ 'execute': 'nbd-server-start',
> > > > -  'arguments': {'addr': {'type': 'inet', 'data': {'host': 'xx.xx.xx.xx', 'port':
> > > > '8889'} } } -}
> > > > -{'execute': 'nbd-server-add', 'arguments': {'device':
> > > > 'secondary-disk0',
> > > > 'writable': true } }
> > > > +{'execute': 'nbd-server-start', 'arguments': {'addr': {'type':
> > > > +'inet',
> > > > +'data': {'host': '0.0.0.0', 'port': '9999'} } } }
> > > > +{'execute': 'nbd-server-add', 'arguments': {'device': 'parent0',
> > > > +'writable': true } }
> > > >
> > > >  Note:
> > > >    a. The qmp command nbd-server-start and nbd-server-add must be
> > > > run @@ -182,44 +212,113 @@ Note:
> > > >       same.
> > > >    c. It is better to put active disk and hidden disk in ramdisk.
> > > >
> > > > -3. On Primary VM's QEMU monitor, issue command:
> > > > +4. On Primary VM's QEMU monitor, issue command:
> > > >  {'execute':'qmp_capabilities'}
> > > > -{ 'execute': 'human-monitor-command',
> > > > -  'arguments': {'command-line': 'drive_add -n buddy
> > > > driver=replication,mode=primary,file.driver=nbd,file.host=xx.xx.xx.x
> > > > x,file.p
> > > > ort=8889,file.export=secondary-disk0,node-name=nbd_client0'}}
> > > > -{ 'execute':'x-blockdev-change', 'arguments':{'parent':
> > > > 'primary-disk0',
> > > > 'node': 'nbd_client0' } } -{ 'execute': 'migrate-set-capabilities',
> > > > -      'arguments': {'capabilities': [ {'capability': 'x-colo', 'state': true } ] } }
> > > > -{ 'execute': 'migrate', 'arguments': {'uri': 'tcp:xx.xx.xx.xx:8888'
> > > > } }
> > > > +{'execute': 'human-monitor-command', 'arguments': {'command-line':
> > > > +'drive_add -n buddy
> > > > +driver=replication,mode=primary,file.driver=nbd,file.host=127.0.0.2
> > > > +,fil e.port=9999,file.export=parent0,node-name=replication0'}}
> > > > +{'execute': 'x-blockdev-change', 'arguments':{'parent':
> > > > +'colo-disk0',
> > > > +'node': 'replication0' } }
> > > > +{'execute': 'migrate-set-capabilities', 'arguments':
> > > > +{'capabilities': [
> > > > +{'capability': 'x-colo', 'state': true } ] } }
> > > > +{'execute': 'migrate', 'arguments': {'uri': 'tcp:127.0.0.2:9998' }
> > > > +}
> > > >
> > > >    Note:
> > > >    a. There should be only one NBD Client for each primary disk.
> > > > -  b. xx.xx.xx.xx is the secondary physical machine's hostname or IP
> > > > -  c. The qmp command line must be run after running qmp command
> > > > line in
> > > > +  b. The qmp command line must be run after running qmp command
> > > > + line in
> > > >       secondary qemu.
> > > >
> > > > -4. After the above steps, you will see, whenever you make changes
> > > > to PVM, SVM will be synced.
> > > > +5. After the above steps, you will see, whenever you make changes
> > > > +to PVM,
> > > > SVM will be synced.
> > > >  You can issue command '{ "execute": "migrate-set-parameters" ,
> > > > "arguments":{ "x-checkpoint-delay": 2000 } }'
> > > > -to change the checkpoint period time
> > > > +to change the idle checkpoint period time
> > > > +
> > > > +6. Failover test
> > > > +You can kill one of the VMs and Failover on the surviving VM:
> > > > +
> > > > +If you killed the Secondary, then follow "Primary Failover". After
> > > > +that, if you want to resume the replication, follow "Primary resume
> > > > replication"
> > > > +
> > > > +If you killed the Primary, then follow "Secondary Failover". After
> > > > +that, if you want to resume the replication, follow "Secondary
> > > > +resume
> > > > replication"
> > > > +
> > > > +== Primary Failover ==
> > > > +The Secondary died, resume on the Primary
> > > > +
> > > > +{'execute': 'x-blockdev-change', 'arguments':{ 'parent':
> > > > +'colo-disk0',
> > > > +'child': 'children.1'} }
> > > > +{'execute': 'human-monitor-command', 'arguments':{ 'command-line':
> > > > +'drive_del replication0' } }
> > > > +{'execute': 'object-del', 'arguments':{ 'id': 'comp0' } }
> > > > +{'execute': 'object-del', 'arguments':{ 'id': 'iothread1' } }
> > > > +{'execute': 'object-del', 'arguments':{ 'id': 'm0' } }
> > > > +{'execute': 'object-del', 'arguments':{ 'id': 'redire0' } }
> > > > +{'execute': 'object-del', 'arguments':{ 'id': 'redire1' } }
> > > > +{'execute': 'x-colo-lost-heartbeat' }
> > > > +
> > > > +== Secondary Failover ==
> > > > +The Primary died, resume on the Secondary and prepare to become the
> > > > new
> > > > +Primary
> > > > +
> > > > +{'execute': 'nbd-server-stop'}
> > > > +{'execute': 'x-colo-lost-heartbeat'}
> > > > +
> > > > +{'execute': 'object-del', 'arguments':{ 'id': 'f2' } }
> > > > +{'execute': 'object-del', 'arguments':{ 'id': 'f1' } }
> > > > +{'execute': 'chardev-remove', 'arguments':{ 'id': 'red1' } }
> > > > +{'execute': 'chardev-remove', 'arguments':{ 'id': 'red0' } }
> > > > +
> > > > +{'execute': 'chardev-add', 'arguments':{ 'id': 'mirror0', 'backend':
> > > > +{'type': 'socket', 'data': {'addr': { 'type': 'inet', 'data': { 'host':
> > > > +'0.0.0.0', 'port': '9003' } }, 'server': true } } } }  
> > >
> > > Same like I said before.
> > >
> > > Others statement looks good for me.
> > >
> > > Thanks
> > > Zhang Chen
> > >  
> > > > +{'execute': 'chardev-add', 'arguments':{ 'id': 'compare1', 'backend':
> > > > +{'type': 'socket', 'data': {'addr': { 'type': 'inet', 'data': { 'host':
> > > > +'0.0.0.0', 'port': '9004' } }, 'server': true } } } }
> > > > +{'execute': 'chardev-add', 'arguments':{ 'id': 'compare0', 'backend':
> > > > +{'type': 'socket', 'data': {'addr': { 'type': 'inet', 'data': { 'host':
> > > > +'127.0.0.1', 'port': '9001' } }, 'server': true } } } }
> > > > +{'execute': 'chardev-add', 'arguments':{ 'id': 'compare0-0', 'backend':
> > > > +{'type': 'socket', 'data': {'addr': { 'type': 'inet', 'data': { 'host':
> > > > +'127.0.0.1', 'port': '9001' } }, 'server': false } } } }
> > > > +{'execute': 'chardev-add', 'arguments':{ 'id': 'compare_out',
> > > > +'backend': {'type': 'socket', 'data': {'addr': { 'type': 'inet',
> > > > +'data': { 'host': '127.0.0.1', 'port': '9005' } }, 'server': true }
> > > > +} } }
> > > > +{'execute': 'chardev-add', 'arguments':{ 'id': 'compare_out0',
> > > > +'backend': {'type': 'socket', 'data': {'addr': { 'type': 'inet',
> > > > +'data': { 'host': '127.0.0.1', 'port': '9005' } }, 'server': false
> > > > +} } } }
> > > > +
> > > > +== Primary resume replication ==
> > > > +Resume replication after new Secondary is up.
> > > > +
> > > > +Start the new Secondary (Steps 2 and 3 above), then on the Primary:
> > > > +{'execute': 'drive-mirror', 'arguments':{ 'device': 'colo-disk0',
> > > > +'job-id': 'resync', 'target': 'nbd://127.0.0.2:9999/parent0', 'mode':
> > > > +'existing', 'format': 'raw', 'sync': 'full'} }
> > > > +
> > > > +Wait until disk is synced, then:
> > > > +{'execute': 'stop'}
> > > > +{'execute': 'block-job-cancel', 'arguments':{ 'device': 'resync'} }
> > > > +
> > > > +{'execute': 'human-monitor-command', 'arguments':{ 'command-line':
> > > > +'drive_add -n buddy
> > > > +driver=replication,mode=primary,file.driver=nbd,file.host=127.0.0.2
> > > > +,fil e.port=9999,file.export=parent0,node-name=replication0'}}
> > > > +{'execute': 'x-blockdev-change', 'arguments':{ 'parent':
> > > > +'colo-disk0',
> > > > +'node': 'replication0' } }
> > > > +
> > > > +{'execute': 'object-add', 'arguments':{ 'qom-type':
> > > > +'filter-mirror',
> > > > +'id': 'm0', 'props': { 'netdev': 'hn0', 'queue': 'tx', 'outdev':
> > > > +'mirror0' } } }
> > > > +{'execute': 'object-add', 'arguments':{ 'qom-type':
> > > > +'filter-redirector', 'id': 'redire0', 'props': { 'netdev': 'hn0',
> > > > +'queue': 'rx', 'indev': 'compare_out' } } }
> > > > +{'execute': 'object-add', 'arguments':{ 'qom-type':
> > > > +'filter-redirector', 'id': 'redire1', 'props': { 'netdev': 'hn0',
> > > > +'queue': 'rx', 'outdev': 'compare0' } } }
> > > > +{'execute': 'object-add', 'arguments':{ 'qom-type': 'iothread', 'id':
> > > > +'iothread1' } }
> > > > +{'execute': 'object-add', 'arguments':{ 'qom-type': 'colo-compare',
> > > > +'id': 'comp0', 'props': { 'primary_in': 'compare0-0', 'secondary_in':
> > > > +'compare1', 'outdev': 'compare_out0', 'iothread': 'iothread1' } } }
> > > > +
> > > > +{'execute': 'migrate-set-capabilities', 'arguments':{
> > > > +'capabilities': [
> > > > +{'capability': 'x-colo', 'state': true } ] } }
> > > > +{'execute': 'migrate', 'arguments':{ 'uri': 'tcp:127.0.0.2:9998' }
> > > > +}
> > > > +
> > > > +Note:
> > > > +If this Primary previously was a Secondary, then we need to insert
> > > > +the filters before the filter-rewriter by using the
> > > > +"'insert': 'before', 'position': 'id=rew0'" Options. See below.
> > > > +
> > > > +== Secondary resume replication ==
> > > > +Become Primary and resume replication after new Secondary is up.
> > > > +Note that now 127.0.0.1 is the Secondary and 127.0.0.2 is the Primary.
> > > > +
> > > > +Start the new Secondary (Steps 2 and 3 above, but with
> > > > +primary_ip=127.0.0.2), then on the old Secondary:
> > > > +{'execute': 'drive-mirror', 'arguments':{ 'device': 'colo-disk0',
> > > > +'job-id': 'resync', 'target': 'nbd://127.0.0.1:9999/parent0', 'mode':
> > > > +'existing', 'format': 'raw', 'sync': 'full'} }
> > > > +
> > > > +Wait until disk is synced, then:
> > > > +{'execute': 'stop'}
> > > > +{'execute': 'block-job-cancel', 'arguments':{ 'device': 'resync' }
> > > > +}
> > > >
> > > > -5. Failover test
> > > > -You can kill Primary VM and run 'x_colo_lost_heartbeat' in
> > > > Secondary VM's - monitor at the same time, then SVM will failover
> > > > and client will not detect this -change.
> > > > +{'execute': 'human-monitor-command', 'arguments':{ 'command-line':
> > > > +'drive_add -n buddy
> > > > +driver=replication,mode=primary,file.driver=nbd,file.host=127.0.0.1
> > > > +,fil e.port=9999,file.export=parent0,node-name=replication0'}}
> > > > +{'execute': 'x-blockdev-change', 'arguments':{ 'parent':
> > > > +'colo-disk0',
> > > > +'node': 'replication0' } }
> > > >
> > > > -Before issuing '{ "execute": "x-colo-lost-heartbeat" }' command, we
> > > > have to -issue block related command to stop block replication.
> > > > -Primary:
> > > > -  Remove the nbd child from the quorum:
> > > > -  { 'execute': 'x-blockdev-change', 'arguments': {'parent': 'colo-disk0',  
> > 'child':  
> > > > 'children.1'}}
> > > > -  { 'execute': 'human-monitor-command','arguments': {'command-line':
> > > > 'drive_del blk-buddy0'}}
> > > > -  Note: there is no qmp command to remove the blockdev now
> > > > +{'execute': 'object-add', 'arguments':{ 'qom-type':
> > > > +'filter-mirror',
> > > > +'id': 'm0', 'props': { 'insert': 'before', 'position': 'id=rew0',
> > > > +'netdev': 'hn0', 'queue': 'tx', 'outdev': 'mirror0' } } }
> > > > +{'execute': 'object-add', 'arguments':{ 'qom-type':
> > > > +'filter-redirector', 'id': 'redire0', 'props': { 'insert':
> > > > +'before',
> > > > +'position': 'id=rew0', 'netdev': 'hn0', 'queue': 'rx', 'indev':
> > > > +'compare_out' } } }
> > > > +{'execute': 'object-add', 'arguments':{ 'qom-type':
> > > > +'filter-redirector', 'id': 'redire1', 'props': { 'insert':
> > > > +'before',
> > > > +'position': 'id=rew0', 'netdev': 'hn0', 'queue': 'rx', 'outdev':
> > > > +'compare0' } } }
> > > > +{'execute': 'object-add', 'arguments':{ 'qom-type': 'iothread', 'id':
> > > > +'iothread1' } }
> > > > +{'execute': 'object-add', 'arguments':{ 'qom-type': 'colo-compare',
> > > > +'id': 'comp0', 'props': { 'primary_in': 'compare0-0', 'secondary_in':
> > > > +'compare1', 'outdev': 'compare_out0', 'iothread': 'iothread1' } } }
> > > >
> > > > -Secondary:
> > > > -  The primary host is down, so we should do the following thing:
> > > > -  { 'execute': 'nbd-server-stop' }
> > > > +{'execute': 'migrate-set-capabilities', 'arguments':{
> > > > +'capabilities': [
> > > > +{'capability': 'x-colo', 'state': true } ] } }
> > > > +{'execute': 'migrate', 'arguments':{ 'uri': 'tcp:127.0.0.1:9998' }
> > > > +}
> > > >
> > > >  == TODO ==
> > > > -1. Support continuous VM replication.
> > > > -2. Support shared storage.
> > > > -3. Develop the heartbeat part.
> > > > -4. Reduce checkpoint VM’s downtime while doing checkpoint.
> > > > +1. Support shared storage.
> > > > +2. Develop the heartbeat part.
> > > > +3. Reduce checkpoint VM’s downtime while doing checkpoint.

Zhang Chen Oct. 11, 2019, 5:39 p.m. UTC | #5

> -----Original Message-----
> From: Lukas Straub <[e-mail]>
> Sent: Saturday, October 12, 2019 12:01 AM
> To: Zhang, Chen <[e-mail]>
> Cc: qemu-devel <[e-mail]>; Jason Wang
> <[e-mail]>; Wen Congyang <[e-mail]>;
> Xie Changlong <[e-mail]>; Kevin Wolf
> <[e-mail]>; Max Reitz <[e-mail]>; qemu-block
> <[e-mail]>
> Subject: Re: [PATCH v6 4/4] colo: Update Documentation for continuous
> replication
> 
> On Thu, 10 Oct 2019 10:34:15 +0000
> "Zhang, Chen" <[e-mail]> wrote:
> 
> > > -----Original Message-----
> > > From: Lukas Straub <[e-mail]>
> > > Sent: Wednesday, October 9, 2019 11:17 PM
> > > To: Zhang, Chen <[e-mail]>
> > > Cc: qemu-devel <[e-mail]>; Jason Wang
> > > <[e-mail]>; Wen Congyang
> <[e-mail]>; Xie
> > > Changlong <[e-mail]>; Kevin Wolf
> <[e-mail]>;
> > > Max Reitz <[e-mail]>; qemu-block <qemu-
> [e-mail]>
> > > Subject: Re: [PATCH v6 4/4] colo: Update Documentation for
> > > continuous replication
> > >
> > > On Wed, 9 Oct 2019 08:36:52 +0000
> > > "Zhang, Chen" <[e-mail]> wrote:
> > >
> > > > > -----Original Message-----
> > > > > From: Lukas Straub <[e-mail]>
> > > > > Sent: Saturday, October 5, 2019 9:06 PM
> > > > > To: qemu-devel <[e-mail]>
> > > > > Cc: Zhang, Chen <[e-mail]>; Jason Wang
> > > > > <[e-mail]>; Wen Congyang
> > > <[e-mail]>; Xie
> > > > > Changlong <[e-mail]>; Kevin Wolf
> > > <[e-mail]>;
> > > > > Max Reitz <[e-mail]>; qemu-block <qemu-
> > > [e-mail]>
> > > > > Subject: [PATCH v6 4/4] colo: Update Documentation for
> > > > > continuous replication
> > > > >
> > > > > Document the qemu command-line and qmp commands for
> continuous
> > > > > replication
> > > > >
> > > > > Signed-off-by: Lukas Straub <[e-mail]>
> > > > > ---
> > > > >  docs/COLO-FT.txt           | 213 +++++++++++++++++++++++++++------
> ----
> > > > >  docs/block-replication.txt |  28 +++--
> > > > >  2 files changed, 174 insertions(+), 67 deletions(-)
> > > > >
> > > > > diff --git a/docs/COLO-FT.txt b/docs/COLO-FT.txt index
> > > > > ad24680d13..bc1a0ccb99 100644
> > > > > --- a/docs/COLO-FT.txt
> > > > > +++ b/docs/COLO-FT.txt
> > > > > @@ -145,35 +145,65 @@ The diagram just shows the main qmp
> > > command,
> > > > > you can get the detail  in test procedure.
> > > > >
> > > > > ...
> > > > >
> > > > > +Note: Here we are running both instances on the same Host for
> > > > > +testing, change the IP Addresses if you want to run it on two
> > > > > +Hosts. Initally
> > > > > +127.0.0.1 is the Primary Host and 127.0.0.2 is the Secondary Host.
> > > > > +
> > > > > +== Startup qemu ==
> > > > > +1. Primary:
> > > > > +Note: Initally, $imagefolder/primary.qcow2 needs to be copied
> > > > > +to all
> > > Hosts.
> > > > > +# imagefolder="/mnt/vms/colo-test-primary"
> > > > > +
> > > > > +# qemu-system-x86_64 -enable-kvm -cpu qemu64,+kvmclock -m
> 512 -
> > > smp
> > > > > 1 -qmp stdio \
> > > > > +   -device piix3-usb-uhci -device usb-tablet -name primary \
> > > > > +   -netdev
> > > > > + tap,id=hn0,vhost=off,helper=/usr/lib/qemu/qemu-bridge-helper
> > > > > \
> > > > > +   -device rtl8139,id=e0,netdev=hn0 \
> > > > > +   -chardev socket,id=mirror0,host=0.0.0.0,port=9003,server,nowait \
> > > > > +   -chardev
> > > > > + socket,id=compare1,host=0.0.0.0,port=9004,server,wait \
> > > >
> > > > We should change the host=127.0.0.1 consistent with the expression
> below.
> > >
> > > Hi,
> > > This (and the IPs below in the QMP commands) needs to be this way,
> > > because it's a listening port and with 127.0.0.1 it would only
> > > listen on the loopback ip and wouldn't be reachable from another
> > > node for example. With
> > > 0.0.0.0 it will listen on all Interfaces.
> >
> > Yes, I know.  For this command demo, maybe use 192.168.0.1/192.168.0.2
> are more clear.
> 
> Hmm,
> the compare0 and compare_out actually can be replaced by unix sockets.
> So what do you think about the following?
> 
>    -chardev socket,id=mirror0,host=127.0.0.1,port=9003,server,nowait \
>    -chardev socket,id=compare1,host=127.0.0.1,port=9004,server,wait \
>    -chardev socket,id=compare0,path=/tmp/compare0.sock,server,nowait \
>    -chardev socket,id=compare0-0,path=/tmp/compare0.sock \
>    -chardev
> socket,id=compare_out,path=/tmp/compare_out.sock,server,nowait \
>    -chardev socket,id=compare_out0,path=/tmp/compare_out.sock \

In this way, user must create the unix socket node before start COLO, it is very hard to use.
I re-considered the issue here, looks keep the 0.0.0.0 is a relatively reasonably choice.
We can add some note here like you said before, to make sure user know the means of 0.0.0.0. 

Thanks
Zhang Chen

> 
> > >
> > > > > +   -chardev
> > > > > + socket,id=compare0,host=127.0.0.1,port=9001,server,nowait
> > > \
> > > > > +   -chardev socket,id=compare0-0,host=127.0.0.1,port=9001 \
> > > > > +   -chardev
> > > > > + socket,id=compare_out,host=127.0.0.1,port=9005,server,nowait
> > > > > \
> > > > > +   -chardev socket,id=compare_out0,host=127.0.0.1,port=9005 \
> > > > > +   -object filter-mirror,id=m0,netdev=hn0,queue=tx,outdev=mirror0
> \
> > > > > +   -object filter-
> > > > > redirector,netdev=hn0,id=redire0,queue=rx,indev=compare_out \
> > > > > +   -object filter-
> > > > > redirector,netdev=hn0,id=redire1,queue=rx,outdev=compare0 \
> > > > > +   -object iothread,id=iothread1 \
> > > > > +   -object
> > > > > +colo-compare,id=comp0,primary_in=compare0-
> > > > > 0,secondary_in=compare1,\
> > > > > +outdev=compare_out0,iothread=iothread1 \
> > > > > +   -drive
> > > > > +if=ide,id=colo-disk0,driver=quorum,read-pattern=fifo,vote-thres
> > > > > +hold
> > > > > +=1,\
> > > > > +children.0.file.filename=$imagefolder/primary.qcow2,children.0.
> > > > > +driv
> > > > > +er=q
> > > > > +cow2 -S
> > > > > +
> > > > > +2. Secondary:
> > > > > +# imagefolder="/mnt/vms/colo-test-secondary"
> > > > > +# primary_ip=127.0.0.1
> > > > > +
> > > > > +# qemu-img create -f qcow2 $imagefolder/secondary-active.qcow2
> > > > > +10G
> > > > > +
> > > > > +# qemu-img create -f qcow2 $imagefolder/secondary-hidden.qcow2
> > > 10G
> > > > > +
> > > >
> > > > The active disk and hidden disk just need create one time, we can
> > > > note that
> > > here.
> > >
> > > Ok, I will Note that. But I will wait until the block changes are
> > > reviewed before sending the next version.
> >
> > That's fine for me.
> >
> > Thanks
> > Zhang Chen
> >
> > >
> > > Regards,
> > > Lukas Straub
> > >
> > > > > +# qemu-system-x86_64 -enable-kvm -cpu qemu64,+kvmclock -m
> 512 -
> > > smp
> > > > > 1 -qmp stdio \
> > > > > +   -device piix3-usb-uhci -device usb-tablet -name secondary \
> > > > > +   -netdev
> > > > > + tap,id=hn0,vhost=off,helper=/usr/lib/qemu/qemu-bridge-helper
> > > > > \
> > > > > +   -device rtl8139,id=e0,netdev=hn0 \
> > > > > +   -chardev socket,id=red0,host=$primary_ip,port=9003,reconnect=1
> \
> > > > > +   -chardev socket,id=red1,host=$primary_ip,port=9004,reconnect=1
> \
> > > > > +   -object filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0 \
> > > > > +   -object filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1
> \
> > > > > +   -object filter-rewriter,id=rew0,netdev=hn0,queue=all \
> > > > > +   -drive
> > > > > if=none,id=parent0,file.filename=$imagefolder/primary.qcow2,driv
> > > > > er=q
> > > > > cow
> > > > > 2 \
> > > > > +   -drive
> > > > > +if=none,id=childs0,driver=replication,mode=secondary,file.drive
> > > > > +r=qc
> > > > > +ow2,
> > > > > +\
> > > > > +top-id=childs0,file.file.filename=$imagefolder/secondary-active
> > > > > +.qco
> > > > > +w2,\
> > > > > +file.backing.driver=qcow2,file.backing.file.filename=$imagefold
> > > > > +er/s
> > > > > +econ
> > > > > +dary-hidden.qcow2,\
> > > > > +file.backing.backing=parent0 \
> > > > > +   -drive
> > > > > +if=ide,id=colo-disk0,driver=quorum,read-pattern=fifo,vote-thres
> > > > > +hold
> > > > > +=1,\
> > > > > +children.0=childs0 \
> > > > > +   -incoming tcp:0.0.0.0:9998
> > > > > +
> > > > > +
> > > > > +3. On Secondary VM's QEMU monitor, issue command
> > > > >  {'execute':'qmp_capabilities'}
> > > > > -{ 'execute': 'nbd-server-start',
> > > > > -  'arguments': {'addr': {'type': 'inet', 'data': {'host': 'xx.xx.xx.xx', 'port':
> > > > > '8889'} } } -}
> > > > > -{'execute': 'nbd-server-add', 'arguments': {'device':
> > > > > 'secondary-disk0',
> > > > > 'writable': true } }
> > > > > +{'execute': 'nbd-server-start', 'arguments': {'addr': {'type':
> > > > > +'inet',
> > > > > +'data': {'host': '0.0.0.0', 'port': '9999'} } } }
> > > > > +{'execute': 'nbd-server-add', 'arguments': {'device':
> > > > > +'parent0',
> > > > > +'writable': true } }
> > > > >
> > > > >  Note:
> > > > >    a. The qmp command nbd-server-start and nbd-server-add must
> > > > > be run @@ -182,44 +212,113 @@ Note:
> > > > >       same.
> > > > >    c. It is better to put active disk and hidden disk in ramdisk.
> > > > >
> > > > > -3. On Primary VM's QEMU monitor, issue command:
> > > > > +4. On Primary VM's QEMU monitor, issue command:
> > > > >  {'execute':'qmp_capabilities'}
> > > > > -{ 'execute': 'human-monitor-command',
> > > > > -  'arguments': {'command-line': 'drive_add -n buddy
> > > > > driver=replication,mode=primary,file.driver=nbd,file.host=xx.xx.
> > > > > xx.x
> > > > > x,file.p
> > > > > ort=8889,file.export=secondary-disk0,node-name=nbd_client0'}}
> > > > > -{ 'execute':'x-blockdev-change', 'arguments':{'parent':
> > > > > 'primary-disk0',
> > > > > 'node': 'nbd_client0' } } -{ 'execute': 'migrate-set-capabilities',
> > > > > -      'arguments': {'capabilities': [ {'capability': 'x-colo', 'state': true } ] } }
> > > > > -{ 'execute': 'migrate', 'arguments': {'uri': 'tcp:xx.xx.xx.xx:8888'
> > > > > } }
> > > > > +{'execute': 'human-monitor-command', 'arguments': {'command-
> line':
> > > > > +'drive_add -n buddy
> > > > > +driver=replication,mode=primary,file.driver=nbd,file.host=127.0
> > > > > +.0.2 ,fil
> > > > > +e.port=9999,file.export=parent0,node-name=replication0'}}
> > > > > +{'execute': 'x-blockdev-change', 'arguments':{'parent':
> > > > > +'colo-disk0',
> > > > > +'node': 'replication0' } }
> > > > > +{'execute': 'migrate-set-capabilities', 'arguments':
> > > > > +{'capabilities': [
> > > > > +{'capability': 'x-colo', 'state': true } ] } }
> > > > > +{'execute': 'migrate', 'arguments': {'uri':
> > > > > +'tcp:127.0.0.2:9998' } }
> > > > >
> > > > >    Note:
> > > > >    a. There should be only one NBD Client for each primary disk.
> > > > > -  b. xx.xx.xx.xx is the secondary physical machine's hostname
> > > > > or IP
> > > > > -  c. The qmp command line must be run after running qmp command
> > > > > line in
> > > > > +  b. The qmp command line must be run after running qmp
> command
> > > > > + line in
> > > > >       secondary qemu.
> > > > >
> > > > > -4. After the above steps, you will see, whenever you make
> > > > > changes to PVM, SVM will be synced.
> > > > > +5. After the above steps, you will see, whenever you make
> > > > > +changes to PVM,
> > > > > SVM will be synced.
> > > > >  You can issue command '{ "execute": "migrate-set-parameters" ,
> > > > > "arguments":{ "x-checkpoint-delay": 2000 } }'
> > > > > -to change the checkpoint period time
> > > > > +to change the idle checkpoint period time
> > > > > +
> > > > > +6. Failover test
> > > > > +You can kill one of the VMs and Failover on the surviving VM:
> > > > > +
> > > > > +If you killed the Secondary, then follow "Primary Failover".
> > > > > +After that, if you want to resume the replication, follow
> > > > > +"Primary resume
> > > > > replication"
> > > > > +
> > > > > +If you killed the Primary, then follow "Secondary Failover".
> > > > > +After that, if you want to resume the replication, follow
> > > > > +"Secondary resume
> > > > > replication"
> > > > > +
> > > > > +== Primary Failover ==
> > > > > +The Secondary died, resume on the Primary
> > > > > +
> > > > > +{'execute': 'x-blockdev-change', 'arguments':{ 'parent':
> > > > > +'colo-disk0',
> > > > > +'child': 'children.1'} }
> > > > > +{'execute': 'human-monitor-command', 'arguments':{ 'command-
> line':
> > > > > +'drive_del replication0' } }
> > > > > +{'execute': 'object-del', 'arguments':{ 'id': 'comp0' } }
> > > > > +{'execute': 'object-del', 'arguments':{ 'id': 'iothread1' } }
> > > > > +{'execute': 'object-del', 'arguments':{ 'id': 'm0' } }
> > > > > +{'execute': 'object-del', 'arguments':{ 'id': 'redire0' } }
> > > > > +{'execute': 'object-del', 'arguments':{ 'id': 'redire1' } }
> > > > > +{'execute': 'x-colo-lost-heartbeat' }
> > > > > +
> > > > > +== Secondary Failover ==
> > > > > +The Primary died, resume on the Secondary and prepare to become
> > > > > +the
> > > > > new
> > > > > +Primary
> > > > > +
> > > > > +{'execute': 'nbd-server-stop'}
> > > > > +{'execute': 'x-colo-lost-heartbeat'}
> > > > > +
> > > > > +{'execute': 'object-del', 'arguments':{ 'id': 'f2' } }
> > > > > +{'execute': 'object-del', 'arguments':{ 'id': 'f1' } }
> > > > > +{'execute': 'chardev-remove', 'arguments':{ 'id': 'red1' } }
> > > > > +{'execute': 'chardev-remove', 'arguments':{ 'id': 'red0' } }
> > > > > +
> > > > > +{'execute': 'chardev-add', 'arguments':{ 'id': 'mirror0', 'backend':
> > > > > +{'type': 'socket', 'data': {'addr': { 'type': 'inet', 'data': { 'host':
> > > > > +'0.0.0.0', 'port': '9003' } }, 'server': true } } } }
> > > >
> > > > Same like I said before.
> > > >
> > > > Others statement looks good for me.
> > > >
> > > > Thanks
> > > > Zhang Chen
> > > >
> > > > > +{'execute': 'chardev-add', 'arguments':{ 'id': 'compare1', 'backend':
> > > > > +{'type': 'socket', 'data': {'addr': { 'type': 'inet', 'data': { 'host':
> > > > > +'0.0.0.0', 'port': '9004' } }, 'server': true } } } }
> > > > > +{'execute': 'chardev-add', 'arguments':{ 'id': 'compare0', 'backend':
> > > > > +{'type': 'socket', 'data': {'addr': { 'type': 'inet', 'data': { 'host':
> > > > > +'127.0.0.1', 'port': '9001' } }, 'server': true } } } }
> > > > > +{'execute': 'chardev-add', 'arguments':{ 'id': 'compare0-0', 'backend':
> > > > > +{'type': 'socket', 'data': {'addr': { 'type': 'inet', 'data': { 'host':
> > > > > +'127.0.0.1', 'port': '9001' } }, 'server': false } } } }
> > > > > +{'execute': 'chardev-add', 'arguments':{ 'id': 'compare_out',
> > > > > +'backend': {'type': 'socket', 'data': {'addr': { 'type':
> > > > > +'inet',
> > > > > +'data': { 'host': '127.0.0.1', 'port': '9005' } }, 'server':
> > > > > +true } } } }
> > > > > +{'execute': 'chardev-add', 'arguments':{ 'id': 'compare_out0',
> > > > > +'backend': {'type': 'socket', 'data': {'addr': { 'type':
> > > > > +'inet',
> > > > > +'data': { 'host': '127.0.0.1', 'port': '9005' } }, 'server':
> > > > > +false } } } }
> > > > > +
> > > > > +== Primary resume replication == Resume replication after new
> > > > > +Secondary is up.
> > > > > +
> > > > > +Start the new Secondary (Steps 2 and 3 above), then on the Primary:
> > > > > +{'execute': 'drive-mirror', 'arguments':{ 'device':
> > > > > +'colo-disk0',
> > > > > +'job-id': 'resync', 'target': 'nbd://127.0.0.2:9999/parent0', 'mode':
> > > > > +'existing', 'format': 'raw', 'sync': 'full'} }
> > > > > +
> > > > > +Wait until disk is synced, then:
> > > > > +{'execute': 'stop'}
> > > > > +{'execute': 'block-job-cancel', 'arguments':{ 'device':
> > > > > +'resync'} }
> > > > > +
> > > > > +{'execute': 'human-monitor-command', 'arguments':{ 'command-
> line':
> > > > > +'drive_add -n buddy
> > > > > +driver=replication,mode=primary,file.driver=nbd,file.host=127.0
> > > > > +.0.2 ,fil
> > > > > +e.port=9999,file.export=parent0,node-name=replication0'}}
> > > > > +{'execute': 'x-blockdev-change', 'arguments':{ 'parent':
> > > > > +'colo-disk0',
> > > > > +'node': 'replication0' } }
> > > > > +
> > > > > +{'execute': 'object-add', 'arguments':{ 'qom-type':
> > > > > +'filter-mirror',
> > > > > +'id': 'm0', 'props': { 'netdev': 'hn0', 'queue': 'tx', 'outdev':
> > > > > +'mirror0' } } }
> > > > > +{'execute': 'object-add', 'arguments':{ 'qom-type':
> > > > > +'filter-redirector', 'id': 'redire0', 'props': { 'netdev':
> > > > > +'hn0',
> > > > > +'queue': 'rx', 'indev': 'compare_out' } } }
> > > > > +{'execute': 'object-add', 'arguments':{ 'qom-type':
> > > > > +'filter-redirector', 'id': 'redire1', 'props': { 'netdev':
> > > > > +'hn0',
> > > > > +'queue': 'rx', 'outdev': 'compare0' } } }
> > > > > +{'execute': 'object-add', 'arguments':{ 'qom-type': 'iothread', 'id':
> > > > > +'iothread1' } }
> > > > > +{'execute': 'object-add', 'arguments':{ 'qom-type':
> > > > > +'colo-compare',
> > > > > +'id': 'comp0', 'props': { 'primary_in': 'compare0-0', 'secondary_in':
> > > > > +'compare1', 'outdev': 'compare_out0', 'iothread': 'iothread1' }
> > > > > +} }
> > > > > +
> > > > > +{'execute': 'migrate-set-capabilities', 'arguments':{
> > > > > +'capabilities': [
> > > > > +{'capability': 'x-colo', 'state': true } ] } }
> > > > > +{'execute': 'migrate', 'arguments':{ 'uri':
> > > > > +'tcp:127.0.0.2:9998' } }
> > > > > +
> > > > > +Note:
> > > > > +If this Primary previously was a Secondary, then we need to
> > > > > +insert the filters before the filter-rewriter by using the
> > > > > +"'insert': 'before', 'position': 'id=rew0'" Options. See below.
> > > > > +
> > > > > +== Secondary resume replication == Become Primary and resume
> > > > > +replication after new Secondary is up.
> > > > > +Note that now 127.0.0.1 is the Secondary and 127.0.0.2 is the Primary.
> > > > > +
> > > > > +Start the new Secondary (Steps 2 and 3 above, but with
> > > > > +primary_ip=127.0.0.2), then on the old Secondary:
> > > > > +{'execute': 'drive-mirror', 'arguments':{ 'device':
> > > > > +'colo-disk0',
> > > > > +'job-id': 'resync', 'target': 'nbd://127.0.0.1:9999/parent0', 'mode':
> > > > > +'existing', 'format': 'raw', 'sync': 'full'} }
> > > > > +
> > > > > +Wait until disk is synced, then:
> > > > > +{'execute': 'stop'}
> > > > > +{'execute': 'block-job-cancel', 'arguments':{ 'device':
> > > > > +'resync' } }
> > > > >
> > > > > -5. Failover test
> > > > > -You can kill Primary VM and run 'x_colo_lost_heartbeat' in
> > > > > Secondary VM's - monitor at the same time, then SVM will
> > > > > failover and client will not detect this -change.
> > > > > +{'execute': 'human-monitor-command', 'arguments':{ 'command-
> line':
> > > > > +'drive_add -n buddy
> > > > > +driver=replication,mode=primary,file.driver=nbd,file.host=127.0
> > > > > +.0.1 ,fil
> > > > > +e.port=9999,file.export=parent0,node-name=replication0'}}
> > > > > +{'execute': 'x-blockdev-change', 'arguments':{ 'parent':
> > > > > +'colo-disk0',
> > > > > +'node': 'replication0' } }
> > > > >
> > > > > -Before issuing '{ "execute": "x-colo-lost-heartbeat" }'
> > > > > command, we have to -issue block related command to stop block
> replication.
> > > > > -Primary:
> > > > > -  Remove the nbd child from the quorum:
> > > > > -  { 'execute': 'x-blockdev-change', 'arguments': {'parent':
> > > > > 'colo-disk0',
> > > 'child':
> > > > > 'children.1'}}
> > > > > -  { 'execute': 'human-monitor-command','arguments': {'command-
> line':
> > > > > 'drive_del blk-buddy0'}}
> > > > > -  Note: there is no qmp command to remove the blockdev now
> > > > > +{'execute': 'object-add', 'arguments':{ 'qom-type':
> > > > > +'filter-mirror',
> > > > > +'id': 'm0', 'props': { 'insert': 'before', 'position':
> > > > > +'id=rew0',
> > > > > +'netdev': 'hn0', 'queue': 'tx', 'outdev': 'mirror0' } } }
> > > > > +{'execute': 'object-add', 'arguments':{ 'qom-type':
> > > > > +'filter-redirector', 'id': 'redire0', 'props': { 'insert':
> > > > > +'before',
> > > > > +'position': 'id=rew0', 'netdev': 'hn0', 'queue': 'rx', 'indev':
> > > > > +'compare_out' } } }
> > > > > +{'execute': 'object-add', 'arguments':{ 'qom-type':
> > > > > +'filter-redirector', 'id': 'redire1', 'props': { 'insert':
> > > > > +'before',
> > > > > +'position': 'id=rew0', 'netdev': 'hn0', 'queue': 'rx', 'outdev':
> > > > > +'compare0' } } }
> > > > > +{'execute': 'object-add', 'arguments':{ 'qom-type': 'iothread', 'id':
> > > > > +'iothread1' } }
> > > > > +{'execute': 'object-add', 'arguments':{ 'qom-type':
> > > > > +'colo-compare',
> > > > > +'id': 'comp0', 'props': { 'primary_in': 'compare0-0', 'secondary_in':
> > > > > +'compare1', 'outdev': 'compare_out0', 'iothread': 'iothread1' }
> > > > > +} }
> > > > >
> > > > > -Secondary:
> > > > > -  The primary host is down, so we should do the following thing:
> > > > > -  { 'execute': 'nbd-server-stop' }
> > > > > +{'execute': 'migrate-set-capabilities', 'arguments':{
> > > > > +'capabilities': [
> > > > > +{'capability': 'x-colo', 'state': true } ] } }
> > > > > +{'execute': 'migrate', 'arguments':{ 'uri':
> > > > > +'tcp:127.0.0.1:9998' } }
> > > > >
> > > > >  == TODO ==
> > > > > -1. Support continuous VM replication.
> > > > > -2. Support shared storage.
> > > > > -3. Develop the heartbeat part.
> > > > > -4. Reduce checkpoint VM’s downtime while doing checkpoint.
> > > > > +1. Support shared storage.
> > > > > +2. Develop the heartbeat part.
> > > > > +3. Reduce checkpoint VM’s downtime while doing checkpoint.

Patch

diff --git a/docs/COLO-FT.txt b/docs/COLO-FT.txt
index ad24680d13..bc1a0ccb99 100644
--- a/docs/COLO-FT.txt
+++ b/docs/COLO-FT.txt
@@ -145,35 +145,65 @@  The diagram just shows the main qmp command, you can get the detail
 in test procedure.
 
 == Test procedure ==
-1. Startup qemu
-Primary:
-# qemu-system-x86_64 -accel kvm -m 2048 -smp 2 -qmp stdio -name primary \
-  -device piix3-usb-uhci -vnc :7 \
-  -device usb-tablet -netdev tap,id=hn0,vhost=off \
-  -device virtio-net-pci,id=net-pci0,netdev=hn0 \
-  -drive if=virtio,id=primary-disk0,driver=quorum,read-pattern=fifo,vote-threshold=1,\
-         children.0.file.filename=1.raw,\
-         children.0.driver=raw -S
-Secondary:
-# qemu-system-x86_64 -accel kvm -m 2048 -smp 2 -qmp stdio -name secondary \
-  -device piix3-usb-uhci -vnc :7 \
-  -device usb-tablet -netdev tap,id=hn0,vhost=off \
-  -device virtio-net-pci,id=net-pci0,netdev=hn0 \
-  -drive if=none,id=secondary-disk0,file.filename=1.raw,driver=raw,node-name=node0 \
-  -drive if=virtio,id=active-disk0,driver=replication,mode=secondary,\
-         file.driver=qcow2,top-id=active-disk0,\
-         file.file.filename=/mnt/ramfs/active_disk.img,\
-         file.backing.driver=qcow2,\
-         file.backing.file.filename=/mnt/ramfs/hidden_disk.img,\
-         file.backing.backing=secondary-disk0 \
-  -incoming tcp:0:8888
-
-2. On Secondary VM's QEMU monitor, issue command
+Note: Here we are running both instances on the same Host for testing,
+change the IP Addresses if you want to run it on two Hosts. Initally
+127.0.0.1 is the Primary Host and 127.0.0.2 is the Secondary Host.
+
+== Startup qemu ==
+1. Primary:
+Note: Initally, $imagefolder/primary.qcow2 needs to be copied to all Hosts.
+# imagefolder="/mnt/vms/colo-test-primary"
+
+# qemu-system-x86_64 -enable-kvm -cpu qemu64,+kvmclock -m 512 -smp 1 -qmp stdio \
+   -device piix3-usb-uhci -device usb-tablet -name primary \
+   -netdev tap,id=hn0,vhost=off,helper=/usr/lib/qemu/qemu-bridge-helper \
+   -device rtl8139,id=e0,netdev=hn0 \
+   -chardev socket,id=mirror0,host=0.0.0.0,port=9003,server,nowait \
+   -chardev socket,id=compare1,host=0.0.0.0,port=9004,server,wait \
+   -chardev socket,id=compare0,host=127.0.0.1,port=9001,server,nowait \
+   -chardev socket,id=compare0-0,host=127.0.0.1,port=9001 \
+   -chardev socket,id=compare_out,host=127.0.0.1,port=9005,server,nowait \
+   -chardev socket,id=compare_out0,host=127.0.0.1,port=9005 \
+   -object filter-mirror,id=m0,netdev=hn0,queue=tx,outdev=mirror0 \
+   -object filter-redirector,netdev=hn0,id=redire0,queue=rx,indev=compare_out \
+   -object filter-redirector,netdev=hn0,id=redire1,queue=rx,outdev=compare0 \
+   -object iothread,id=iothread1 \
+   -object colo-compare,id=comp0,primary_in=compare0-0,secondary_in=compare1,\
+outdev=compare_out0,iothread=iothread1 \
+   -drive if=ide,id=colo-disk0,driver=quorum,read-pattern=fifo,vote-threshold=1,\
+children.0.file.filename=$imagefolder/primary.qcow2,children.0.driver=qcow2 -S
+
+2. Secondary:
+# imagefolder="/mnt/vms/colo-test-secondary"
+# primary_ip=127.0.0.1
+
+# qemu-img create -f qcow2 $imagefolder/secondary-active.qcow2 10G
+
+# qemu-img create -f qcow2 $imagefolder/secondary-hidden.qcow2 10G
+
+# qemu-system-x86_64 -enable-kvm -cpu qemu64,+kvmclock -m 512 -smp 1 -qmp stdio \
+   -device piix3-usb-uhci -device usb-tablet -name secondary \
+   -netdev tap,id=hn0,vhost=off,helper=/usr/lib/qemu/qemu-bridge-helper \
+   -device rtl8139,id=e0,netdev=hn0 \
+   -chardev socket,id=red0,host=$primary_ip,port=9003,reconnect=1 \
+   -chardev socket,id=red1,host=$primary_ip,port=9004,reconnect=1 \
+   -object filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0 \
+   -object filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1 \
+   -object filter-rewriter,id=rew0,netdev=hn0,queue=all \
+   -drive if=none,id=parent0,file.filename=$imagefolder/primary.qcow2,driver=qcow2 \
+   -drive if=none,id=childs0,driver=replication,mode=secondary,file.driver=qcow2,\
+top-id=childs0,file.file.filename=$imagefolder/secondary-active.qcow2,\
+file.backing.driver=qcow2,file.backing.file.filename=$imagefolder/secondary-hidden.qcow2,\
+file.backing.backing=parent0 \
+   -drive if=ide,id=colo-disk0,driver=quorum,read-pattern=fifo,vote-threshold=1,\
+children.0=childs0 \
+   -incoming tcp:0.0.0.0:9998
+
+
+3. On Secondary VM's QEMU monitor, issue command
 {'execute':'qmp_capabilities'}
-{ 'execute': 'nbd-server-start',
-  'arguments': {'addr': {'type': 'inet', 'data': {'host': 'xx.xx.xx.xx', 'port': '8889'} } }
-}
-{'execute': 'nbd-server-add', 'arguments': {'device': 'secondary-disk0', 'writable': true } }
+{'execute': 'nbd-server-start', 'arguments': {'addr': {'type': 'inet', 'data': {'host': '0.0.0.0', 'port': '9999'} } } }
+{'execute': 'nbd-server-add', 'arguments': {'device': 'parent0', 'writable': true } }
 
 Note:
   a. The qmp command nbd-server-start and nbd-server-add must be run
@@ -182,44 +212,113 @@  Note:
      same.
   c. It is better to put active disk and hidden disk in ramdisk.
 
-3. On Primary VM's QEMU monitor, issue command:
+4. On Primary VM's QEMU monitor, issue command:
 {'execute':'qmp_capabilities'}
-{ 'execute': 'human-monitor-command',
-  'arguments': {'command-line': 'drive_add -n buddy driver=replication,mode=primary,file.driver=nbd,file.host=xx.xx.xx.xx,file.port=8889,file.export=secondary-disk0,node-name=nbd_client0'}}
-{ 'execute':'x-blockdev-change', 'arguments':{'parent': 'primary-disk0', 'node': 'nbd_client0' } }
-{ 'execute': 'migrate-set-capabilities',
-      'arguments': {'capabilities': [ {'capability': 'x-colo', 'state': true } ] } }
-{ 'execute': 'migrate', 'arguments': {'uri': 'tcp:xx.xx.xx.xx:8888' } }
+{'execute': 'human-monitor-command', 'arguments': {'command-line': 'drive_add -n buddy driver=replication,mode=primary,file.driver=nbd,file.host=127.0.0.2,file.port=9999,file.export=parent0,node-name=replication0'}}
+{'execute': 'x-blockdev-change', 'arguments':{'parent': 'colo-disk0', 'node': 'replication0' } }
+{'execute': 'migrate-set-capabilities', 'arguments': {'capabilities': [ {'capability': 'x-colo', 'state': true } ] } }
+{'execute': 'migrate', 'arguments': {'uri': 'tcp:127.0.0.2:9998' } }
 
   Note:
   a. There should be only one NBD Client for each primary disk.
-  b. xx.xx.xx.xx is the secondary physical machine's hostname or IP
-  c. The qmp command line must be run after running qmp command line in
+  b. The qmp command line must be run after running qmp command line in
      secondary qemu.
 
-4. After the above steps, you will see, whenever you make changes to PVM, SVM will be synced.
+5. After the above steps, you will see, whenever you make changes to PVM, SVM will be synced.
 You can issue command '{ "execute": "migrate-set-parameters" , "arguments":{ "x-checkpoint-delay": 2000 } }'
-to change the checkpoint period time
+to change the idle checkpoint period time
+
+6. Failover test
+You can kill one of the VMs and Failover on the surviving VM:
+
+If you killed the Secondary, then follow "Primary Failover". After that,
+if you want to resume the replication, follow "Primary resume replication"
+
+If you killed the Primary, then follow "Secondary Failover". After that,
+if you want to resume the replication, follow "Secondary resume replication"
+
+== Primary Failover ==
+The Secondary died, resume on the Primary
+
+{'execute': 'x-blockdev-change', 'arguments':{ 'parent': 'colo-disk0', 'child': 'children.1'} }
+{'execute': 'human-monitor-command', 'arguments':{ 'command-line': 'drive_del replication0' } }
+{'execute': 'object-del', 'arguments':{ 'id': 'comp0' } }
+{'execute': 'object-del', 'arguments':{ 'id': 'iothread1' } }
+{'execute': 'object-del', 'arguments':{ 'id': 'm0' } }
+{'execute': 'object-del', 'arguments':{ 'id': 'redire0' } }
+{'execute': 'object-del', 'arguments':{ 'id': 'redire1' } }
+{'execute': 'x-colo-lost-heartbeat' }
+
+== Secondary Failover ==
+The Primary died, resume on the Secondary and prepare to become the new Primary
+
+{'execute': 'nbd-server-stop'}
+{'execute': 'x-colo-lost-heartbeat'}
+
+{'execute': 'object-del', 'arguments':{ 'id': 'f2' } }
+{'execute': 'object-del', 'arguments':{ 'id': 'f1' } }
+{'execute': 'chardev-remove', 'arguments':{ 'id': 'red1' } }
+{'execute': 'chardev-remove', 'arguments':{ 'id': 'red0' } }
+
+{'execute': 'chardev-add', 'arguments':{ 'id': 'mirror0', 'backend': {'type': 'socket', 'data': {'addr': { 'type': 'inet', 'data': { 'host': '0.0.0.0', 'port': '9003' } }, 'server': true } } } }
+{'execute': 'chardev-add', 'arguments':{ 'id': 'compare1', 'backend': {'type': 'socket', 'data': {'addr': { 'type': 'inet', 'data': { 'host': '0.0.0.0', 'port': '9004' } }, 'server': true } } } }
+{'execute': 'chardev-add', 'arguments':{ 'id': 'compare0', 'backend': {'type': 'socket', 'data': {'addr': { 'type': 'inet', 'data': { 'host': '127.0.0.1', 'port': '9001' } }, 'server': true } } } }
+{'execute': 'chardev-add', 'arguments':{ 'id': 'compare0-0', 'backend': {'type': 'socket', 'data': {'addr': { 'type': 'inet', 'data': { 'host': '127.0.0.1', 'port': '9001' } }, 'server': false } } } }
+{'execute': 'chardev-add', 'arguments':{ 'id': 'compare_out', 'backend': {'type': 'socket', 'data': {'addr': { 'type': 'inet', 'data': { 'host': '127.0.0.1', 'port': '9005' } }, 'server': true } } } }
+{'execute': 'chardev-add', 'arguments':{ 'id': 'compare_out0', 'backend': {'type': 'socket', 'data': {'addr': { 'type': 'inet', 'data': { 'host': '127.0.0.1', 'port': '9005' } }, 'server': false } } } }
+
+== Primary resume replication ==
+Resume replication after new Secondary is up.
+
+Start the new Secondary (Steps 2 and 3 above), then on the Primary:
+{'execute': 'drive-mirror', 'arguments':{ 'device': 'colo-disk0', 'job-id': 'resync', 'target': 'nbd://127.0.0.2:9999/parent0', 'mode': 'existing', 'format': 'raw', 'sync': 'full'} }
+
+Wait until disk is synced, then:
+{'execute': 'stop'}
+{'execute': 'block-job-cancel', 'arguments':{ 'device': 'resync'} }
+
+{'execute': 'human-monitor-command', 'arguments':{ 'command-line': 'drive_add -n buddy driver=replication,mode=primary,file.driver=nbd,file.host=127.0.0.2,file.port=9999,file.export=parent0,node-name=replication0'}}
+{'execute': 'x-blockdev-change', 'arguments':{ 'parent': 'colo-disk0', 'node': 'replication0' } }
+
+{'execute': 'object-add', 'arguments':{ 'qom-type': 'filter-mirror', 'id': 'm0', 'props': { 'netdev': 'hn0', 'queue': 'tx', 'outdev': 'mirror0' } } }
+{'execute': 'object-add', 'arguments':{ 'qom-type': 'filter-redirector', 'id': 'redire0', 'props': { 'netdev': 'hn0', 'queue': 'rx', 'indev': 'compare_out' } } }
+{'execute': 'object-add', 'arguments':{ 'qom-type': 'filter-redirector', 'id': 'redire1', 'props': { 'netdev': 'hn0', 'queue': 'rx', 'outdev': 'compare0' } } }
+{'execute': 'object-add', 'arguments':{ 'qom-type': 'iothread', 'id': 'iothread1' } }
+{'execute': 'object-add', 'arguments':{ 'qom-type': 'colo-compare', 'id': 'comp0', 'props': { 'primary_in': 'compare0-0', 'secondary_in': 'compare1', 'outdev': 'compare_out0', 'iothread': 'iothread1' } } }
+
+{'execute': 'migrate-set-capabilities', 'arguments':{ 'capabilities': [ {'capability': 'x-colo', 'state': true } ] } }
+{'execute': 'migrate', 'arguments':{ 'uri': 'tcp:127.0.0.2:9998' } }
+
+Note:
+If this Primary previously was a Secondary, then we need to insert the
+filters before the filter-rewriter by using the
+"'insert': 'before', 'position': 'id=rew0'" Options. See below.
+
+== Secondary resume replication ==
+Become Primary and resume replication after new Secondary is up. Note
+that now 127.0.0.1 is the Secondary and 127.0.0.2 is the Primary.
+
+Start the new Secondary (Steps 2 and 3 above, but with primary_ip=127.0.0.2),
+then on the old Secondary:
+{'execute': 'drive-mirror', 'arguments':{ 'device': 'colo-disk0', 'job-id': 'resync', 'target': 'nbd://127.0.0.1:9999/parent0', 'mode': 'existing', 'format': 'raw', 'sync': 'full'} }
+
+Wait until disk is synced, then:
+{'execute': 'stop'}
+{'execute': 'block-job-cancel', 'arguments':{ 'device': 'resync' } }
 
-5. Failover test
-You can kill Primary VM and run 'x_colo_lost_heartbeat' in Secondary VM's
-monitor at the same time, then SVM will failover and client will not detect this
-change.
+{'execute': 'human-monitor-command', 'arguments':{ 'command-line': 'drive_add -n buddy driver=replication,mode=primary,file.driver=nbd,file.host=127.0.0.1,file.port=9999,file.export=parent0,node-name=replication0'}}
+{'execute': 'x-blockdev-change', 'arguments':{ 'parent': 'colo-disk0', 'node': 'replication0' } }
 
-Before issuing '{ "execute": "x-colo-lost-heartbeat" }' command, we have to
-issue block related command to stop block replication.
-Primary:
-  Remove the nbd child from the quorum:
-  { 'execute': 'x-blockdev-change', 'arguments': {'parent': 'colo-disk0', 'child': 'children.1'}}
-  { 'execute': 'human-monitor-command','arguments': {'command-line': 'drive_del blk-buddy0'}}
-  Note: there is no qmp command to remove the blockdev now
+{'execute': 'object-add', 'arguments':{ 'qom-type': 'filter-mirror', 'id': 'm0', 'props': { 'insert': 'before', 'position': 'id=rew0', 'netdev': 'hn0', 'queue': 'tx', 'outdev': 'mirror0' } } }
+{'execute': 'object-add', 'arguments':{ 'qom-type': 'filter-redirector', 'id': 'redire0', 'props': { 'insert': 'before', 'position': 'id=rew0', 'netdev': 'hn0', 'queue': 'rx', 'indev': 'compare_out' } } }
+{'execute': 'object-add', 'arguments':{ 'qom-type': 'filter-redirector', 'id': 'redire1', 'props': { 'insert': 'before', 'position': 'id=rew0', 'netdev': 'hn0', 'queue': 'rx', 'outdev': 'compare0' } } }
+{'execute': 'object-add', 'arguments':{ 'qom-type': 'iothread', 'id': 'iothread1' } }
+{'execute': 'object-add', 'arguments':{ 'qom-type': 'colo-compare', 'id': 'comp0', 'props': { 'primary_in': 'compare0-0', 'secondary_in': 'compare1', 'outdev': 'compare_out0', 'iothread': 'iothread1' } } }
 
-Secondary:
-  The primary host is down, so we should do the following thing:
-  { 'execute': 'nbd-server-stop' }
+{'execute': 'migrate-set-capabilities', 'arguments':{ 'capabilities': [ {'capability': 'x-colo', 'state': true } ] } }
+{'execute': 'migrate', 'arguments':{ 'uri': 'tcp:127.0.0.1:9998' } }
 
 == TODO ==
-1. Support continuous VM replication.
-2. Support shared storage.
-3. Develop the heartbeat part.
-4. Reduce checkpoint VM’s downtime while doing checkpoint.
+1. Support shared storage.
+2. Develop the heartbeat part.
+3. Reduce checkpoint VM’s downtime while doing checkpoint.
diff --git a/docs/block-replication.txt b/docs/block-replication.txt
index 6bde6737fb..108e9166a8 100644
--- a/docs/block-replication.txt
+++ b/docs/block-replication.txt
@@ -65,12 +65,12 @@  blocks that are already in QEMU.
              ^            ||                            .----------
              |            ||                            | Secondary
         1 Quorum          ||                            '----------
-         /      \         ||
-        /        \        ||
-   Primary    2 filter
-     disk         ^                                                             virtio-blk
-                  |                                                                  ^
-                3 NBD  ------->  3 NBD                                               |
+         /      \         ||                                                           virtio-blk
+        /        \        ||                                                               ^
+   Primary    2 filter                                                                     |
+     disk         ^                                                                   7 Quorum
+                  |                                                                    /
+                3 NBD  ------->  3 NBD                                                /
                 client    ||     server                                          2 filter
                           ||        ^                                                ^
 --------.                 ||        |                                                |
@@ -106,6 +106,10 @@  any state that would otherwise be lost by the speculative write-through
 of the NBD server into the secondary disk. So before block replication,
 the primary disk and secondary disk should contain the same data.
 
+7) The secondary also has a quorum node, so after secondary failover it
+can become the new primary and continue replication.
+
+
 == Failure Handling ==
 There are 7 internal errors when block replication is running:
 1. I/O error on primary disk
@@ -171,16 +175,18 @@  Primary:
      leading whitespace.
   5. The qmp command line must be run after running qmp command line in
      secondary qemu.
-  6. After failover we need remove children.1 (replication driver).
+  6. After primary failover we need remove children.1 (replication driver).
 
 Secondary:
   -drive if=none,driver=raw,file.filename=1.raw,id=colo1 \
-  -drive if=xxx,id=topxxx,driver=replication,mode=secondary,top-id=topxxx\
+  -drive if=none,id=childs1,driver=replication,mode=secondary,top-id=childs1
          file.file.filename=active_disk.qcow2,\
          file.driver=qcow2,\
          file.backing.file.filename=hidden_disk.qcow2,\
          file.backing.driver=qcow2,\
          file.backing.backing=colo1
+  -drive if=xxx,driver=quorum,read-pattern=fifo,id=top-disk1,\
+         vote-threshold=1,children.0=childs1
 
   Then run qmp command in secondary qemu:
     { 'execute': 'nbd-server-start',
@@ -234,6 +240,8 @@  Secondary:
   The primary host is down, so we should do the following thing:
   { 'execute': 'nbd-server-stop' }
 
+Promote Secondary to Primary:
+  see COLO-FT.txt
+
 TODO:
-1. Continuous block replication
-2. Shared disk
+1. Shared disk