diff mbox series

maintenance: add prune-remote-refs task

Message ID pull.1838.git.1734946566885.gitgitgadget@gmail.com (mailing list archive)
State Superseded
Headers show
Series maintenance: add prune-remote-refs task | expand

Commit Message

Shubham Kanodia Dec. 23, 2024, 9:36 a.m. UTC
From: Shubham Kanodia <shubham.kanodia10@gmail.com>

Remote-tracking refs can accumulate in local repositories even as branches
are deleted on remotes, impacting git performance negatively. Existing
alternatives to keep refs pruned have a few issues — 

1. The `fetch.prune` config automatically cleans up remote ref on fetch,
but also pulls in new ref from remote which is an undesirable side-effect.

2.`git remote prune` cleans up refs without adding to the existing list
but requires periodic user intervention.

This adds a new maintenance task 'prune-remote-refs' that runs
'git remote prune' for each configured remote daily. This provides an
automated way to clean up stale remote-tracking refs — especially when
users may not do a full fetch.

This task is disabled by default.

Signed-off-by: Shubham Kanodia <shubham.kanodia10@gmail.com>
---
    maintenance: add prune-remote-refs task
    
    As discussed previously on:
    https://lore.kernel.org/git/xmqqwmfr112w.fsf@gitster.g/T/#t
    
    Remote-tracking refs can accumulate in local repositories even as
    branches are deleted on remotes, impacting git performance negatively.
    Existing alternatives to keep refs pruned have a few issues — 
    
     1. The fetch.prune config automatically cleans up remote ref on fetch,
        but also pulls in new ref from remote which is an undesirable
        side-effect.
    
    2.git remote prune cleans up refs without adding to the existing list
    but requires periodic user intervention.
    
    This adds a new maintenance task 'prune-remote-refs' that runs 'git
    remote prune' for each configured remote daily. This provides an
    automated way to clean up stale remote-tracking refs — especially when
    users may not do a full fetch.
    
    This task is disabled by default.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1838%2Fpastelsky%2Fsk%2Fadd-remote-prune-maintenance-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1838/pastelsky/sk/add-remote-prune-maintenance-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/1838

 Documentation/git-maintenance.txt | 20 ++++++++++++++
 builtin/gc.c                      | 42 +++++++++++++++++++++++++++++
 t/t7900-maintenance.sh            | 44 +++++++++++++++++++++++++++++++
 3 files changed, 106 insertions(+)


base-commit: 063bcebf0c917140ca0e705cbe0fdea127e90086

Comments

Junio C Hamano Dec. 27, 2024, 9:07 a.m. UTC | #1
Thanks for a patch.


"Shubham Kanodia via GitGitGadget" <gitgitgadget@gmail.com> writes:

You'd want to check your procedure to tell GGG about addresses; I am
seeing these

    From: "Shubham Kanodia via GitGitGadget" <gitgitgadget@gmail.com>
    To: git@vger.kernel.org
    Cc: "mailto:gitster@pobox.com" <[gitster@pobox.com]>,
            "mailto:ps@pks.im" <[ps@pks.im]>,
            Shubham Kanodia <shubham.kanodia10@gmail.com>,
            Shubham Kanodia <shubham.kanodia10@gmail.com>

and Cc addresses in it would probably not work as-is (I've fixed
them up manually).

> From: Shubham Kanodia <shubham.kanodia10@gmail.com>
>
> Remote-tracking refs can accumulate in local repositories even as branches
> are deleted on remotes, impacting git performance negatively. Existing
> alternatives to keep refs pruned have a few issues:
>
> 1. The `fetch.prune` config automatically cleans up remote ref on fetch,
> but also pulls in new ref from remote which is an undesirable side-effect.

This makes it sound as if fetch.prune configuration makes new refs
pulled, but that is not what happens and that is not what you wanted
to hint.

	If you run "git fetch" with the "--prune" option (or with
	the fetch.prune configuration set to true) while having the
	default refspec "+refs/heads/*:refs/remotes/$name/*"
	configured in remote.$name.fetch, then ...

> diff --git a/Documentation/git-maintenance.txt b/Documentation/git-maintenance.txt
> index 6e6651309d3..0c8f1e01ccd 100644
> --- a/Documentation/git-maintenance.txt
> +++ b/Documentation/git-maintenance.txt
> @@ -158,6 +158,26 @@ pack-refs::
>  	need to iterate across many references. See linkgit:git-pack-refs[1]
>  	for more information.
>  
> +prune-remote-refs::
> +	The `prune-remote-refs` task runs `git remote prune` on each remote
> +	repository registered in the local repository. This task helps clean
> +	up deleted remote branches, improving the performance of operations
> +	that iterate through the refs. See linkgit:git-remote[1] for more
> +	information. This task is disabled by default.
> ++
> +NOTE: This task is opt-in to prevent unexpected removal of remote refs
> +for users of git-maintenance. For most users, configuring `fetch.prune=true`
> +is a acceptable solution, as it will automatically clean up stale remote-tracking
> +branches during normal fetch operations. However, this task can be useful in
> +specific scenarios:
> ++
> +--
> +* When using selective fetching (e.g., `git fetch origin +foo:refs/remotes/origin/foo`)
> +  where `fetch.prune` would not affect refs outside the fetched hierarchy

The word "hierarchy" hints that things under refs/remotes/origin/
(which is the hierarchy 'foo' is fetched into) that went away would
be pruned, but that is not what happens (otherwise you would not be
adding this feature).

> +* When third-party tools might perform unexpected full fetches, and you want
> +  periodic cleanup independently of fetch operations

You'd want a full-stop after these two sentences, by the way.

> diff --git a/builtin/gc.c b/builtin/gc.c
> index 4ae5196aedf..9acf1d29895 100644
> --- a/builtin/gc.c
> +++ b/builtin/gc.c
> @@ -20,6 +20,7 @@
>  #include "lockfile.h"
>  #include "parse-options.h"
>  #include "run-command.h"
> +#include "remote.h"
>  #include "sigchain.h"
>  #include "strvec.h"
>  #include "commit.h"
> @@ -913,6 +914,40 @@ static int maintenance_opt_schedule(const struct option *opt, const char *arg,
>  	return 0;
>  }
>  
> +static int collect_remote(struct remote *remote, void *cb_data)
> +{
> +	struct string_list *list = cb_data;
> +
> +	if (!remote->url.nr)
> +		return 0;
> +
> +	string_list_append(list, remote->name);
> +	return 0;
> +}
> +
> +static int maintenance_task_prune_remote(struct maintenance_run_opts *opts UNUSED,
> +					 struct gc_config *cfg UNUSED)
> +{
> +	struct string_list_item *item;
> +	struct string_list remotes_list = STRING_LIST_INIT_NODUP;
> +	struct child_process child = CHILD_PROCESS_INIT;
> +	int result = 0;
> +
> +	for_each_remote(collect_remote, &remotes_list);
> +
> +	for_each_string_list_item (item, &remotes_list) {
> +		const char *remote_name = item->string;
> +		child.git_cmd = 1;
> +		strvec_pushl(&child.args, "remote", "prune", remote_name, NULL);
> +
> +		if (run_command(&child))
> +			result = error(_("failed to prune '%s'"), remote_name);
> +	}

Hmph, is there a reason why you need two loops, instead of
for-each-remote calling a function that does the run_command()
thing?

"git grep for_each_string_list_item \*.c" tells me that we almost
never write SP between the macro name and the opening parenthesis.

This loop does not stop at the first error, but returns a non-zero
error after noticing even a single remote fail to run prune, which
sounds like a seneible design.  Would an error percolate up the same
way when two different tasks run and one of them fails in the
control folow in "git maintenance"?  Just want to see if we are
being consistent with the surrounding code.

Thanks.
Shubham Kanodia Dec. 28, 2024, 9:58 a.m. UTC | #2
On Fri, Dec 27, 2024 at 2:37 PM Junio C Hamano <gitster@pobox.com> wrote:
>
> Thanks for a patch.
>
>
> "Shubham Kanodia via GitGitGadget" <gitgitgadget@gmail.com> writes:
>
> You'd want to check your procedure to tell GGG about addresses; I am
> seeing these
>
>     From: "Shubham Kanodia via GitGitGadget" <gitgitgadget@gmail.com>
>     To: git@vger.kernel.org
>     Cc: "mailto:gitster@pobox.com" <[gitster@pobox.com]>,
>             "mailto:ps@pks.im" <[ps@pks.im]>,
>             Shubham Kanodia <shubham.kanodia10@gmail.com>,
>             Shubham Kanodia <shubham.kanodia10@gmail.com>
>
> and Cc addresses in it would probably not work as-is (I've fixed
> them up manually).

I think the GGG comment had a few formatting errors. Thanks for fixing the cc.

> Hmph, is there a reason why you need two loops, instead of
> for-each-remote calling a function that does the run_command()
> thing?

It can be collapsed into one.

> This loop does not stop at the first error, but returns a non-zero
> error after noticing even a single remote fail to run prune, which
> sounds like a seneible design.  Would an error percolate up the same
> way when two different tasks run and one of them fails in the
> control folow in "git maintenance"?  Just want to see if we are
> being consistent with the surrounding code.

Fair point. I'll make the process flow identical to the prefetch refs
task that works similarly across remotes.
It returns as soon as the first remote fails (without necessarily
affecting other tasks).
Junio C Hamano Dec. 28, 2024, 4:05 p.m. UTC | #3
Shubham Kanodia <shubham.kanodia10@gmail.com> writes:

>> Hmph, is there a reason why you need two loops, instead of
>> for-each-remote calling a function that does the run_command()
>> thing?
>
> It can be collapsed into one.

Sorry, but that is not an answer, as my question was not a
suggestion to change anything.

It was a question asking you if there was a specific reason why the
code was structured the way it was written.  If there is another way
to write it, you need to answer why the alternative wasn't picked.

>> This loop does not stop at the first error, but returns a non-zero
>> error after noticing even a single remote fail to run prune, which
>> sounds like a seneible design.  Would an error percolate up the same
>> way when two different tasks run and one of them fails in the
>> control folow in "git maintenance"?  Just want to see if we are
>> being consistent with the surrounding code.
>
> Fair point. I'll make the process flow identical to the prefetch refs
> task that works similarly across remotes.
> It returns as soon as the first remote fails (without necessarily
> affecting other tasks).

... and the first failure signals the caller a failure?  That would
match what you did in your new feature, which is perfect.

Thanks.
Shubham Kanodia Dec. 28, 2024, 4:24 p.m. UTC | #4
On Sat, Dec 28, 2024 at 9:35 PM Junio C Hamano <gitster@pobox.com> wrote:
>
> Shubham Kanodia <shubham.kanodia10@gmail.com> writes:
>
> >> Hmph, is there a reason why you need two loops, instead of
> >> for-each-remote calling a function that does the run_command()
> >> thing?
> >
> > It can be collapsed into one.
>
> Sorry, but that is not an answer, as my question was not a
> suggestion to change anything.
>
> It was a question asking you if there was a specific reason why the
> code was structured the way it was written.  If there is another way
> to write it, you need to answer why the alternative wasn't picked.

There wasn't a good reason for doing it that way. I guess I was trying
to understand the second argument for `for_each_remote` would be best
used if the command was called directly (while avoiding a compilation
warning), but looking at a few other usages of `for_each_remote` I
realised that it could just be marked unused in this case (since we
aren't doing anything with it).

I should've probably looked deeper and learnt from existing patterns
(e.g. `maintenance_task_prefetch`) — which I have in my last patch.

> >> This loop does not stop at the first error, but returns a non-zero
> >> error after noticing even a single remote fail to run prune, which
> >> sounds like a seneible design.  Would an error percolate up the same
> >> way when two different tasks run and one of them fails in the
> >> control folow in "git maintenance"?  Just want to see if we are
> >> being consistent with the surrounding code.
> >
> > Fair point. I'll make the process flow identical to the prefetch refs
> > task that works similarly across remotes.
> > It returns as soon as the first remote fails (without necessarily
> > affecting other tasks).
>
> ... and the first failure signals the caller a failure?  That would
> match what you did in your new feature, which is perfect.

Exactly — the first failing remote will signal that the
`prune-remote-refs` task has failed via an immediate `return 1`.
The maintenance command uses this to register the exit code of the top
level command to 1, while continuing to execute all other tasks
anyway.

Thanks,
Shubham K
diff mbox series

Patch

diff --git a/Documentation/git-maintenance.txt b/Documentation/git-maintenance.txt
index 6e6651309d3..0c8f1e01ccd 100644
--- a/Documentation/git-maintenance.txt
+++ b/Documentation/git-maintenance.txt
@@ -158,6 +158,26 @@  pack-refs::
 	need to iterate across many references. See linkgit:git-pack-refs[1]
 	for more information.
 
+prune-remote-refs::
+	The `prune-remote-refs` task runs `git remote prune` on each remote
+	repository registered in the local repository. This task helps clean
+	up deleted remote branches, improving the performance of operations
+	that iterate through the refs. See linkgit:git-remote[1] for more
+	information. This task is disabled by default.
++
+NOTE: This task is opt-in to prevent unexpected removal of remote refs
+for users of git-maintenance. For most users, configuring `fetch.prune=true`
+is a acceptable solution, as it will automatically clean up stale remote-tracking
+branches during normal fetch operations. However, this task can be useful in
+specific scenarios:
++
+--
+* When using selective fetching (e.g., `git fetch origin +foo:refs/remotes/origin/foo`)
+  where `fetch.prune` would not affect refs outside the fetched hierarchy
+* When third-party tools might perform unexpected full fetches, and you want
+  periodic cleanup independently of fetch operations
+--
+
 OPTIONS
 -------
 --auto::
diff --git a/builtin/gc.c b/builtin/gc.c
index 4ae5196aedf..9acf1d29895 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -20,6 +20,7 @@ 
 #include "lockfile.h"
 #include "parse-options.h"
 #include "run-command.h"
+#include "remote.h"
 #include "sigchain.h"
 #include "strvec.h"
 #include "commit.h"
@@ -913,6 +914,40 @@  static int maintenance_opt_schedule(const struct option *opt, const char *arg,
 	return 0;
 }
 
+static int collect_remote(struct remote *remote, void *cb_data)
+{
+	struct string_list *list = cb_data;
+
+	if (!remote->url.nr)
+		return 0;
+
+	string_list_append(list, remote->name);
+	return 0;
+}
+
+static int maintenance_task_prune_remote(struct maintenance_run_opts *opts UNUSED,
+					 struct gc_config *cfg UNUSED)
+{
+	struct string_list_item *item;
+	struct string_list remotes_list = STRING_LIST_INIT_NODUP;
+	struct child_process child = CHILD_PROCESS_INIT;
+	int result = 0;
+
+	for_each_remote(collect_remote, &remotes_list);
+
+	for_each_string_list_item (item, &remotes_list) {
+		const char *remote_name = item->string;
+		child.git_cmd = 1;
+		strvec_pushl(&child.args, "remote", "prune", remote_name, NULL);
+
+		if (run_command(&child))
+			result = error(_("failed to prune '%s'"), remote_name);
+	}
+
+	string_list_clear(&remotes_list, 0);
+	return result;
+}
+
 /* Remember to update object flag allocation in object.h */
 #define SEEN		(1u<<0)
 
@@ -1375,6 +1410,7 @@  enum maintenance_task_label {
 	TASK_GC,
 	TASK_COMMIT_GRAPH,
 	TASK_PACK_REFS,
+	TASK_PRUNE_REMOTE_REFS,
 
 	/* Leave as final value */
 	TASK__COUNT
@@ -1411,6 +1447,10 @@  static struct maintenance_task tasks[] = {
 		maintenance_task_pack_refs,
 		pack_refs_condition,
 	},
+	[TASK_PRUNE_REMOTE_REFS] = {
+		"prune-remote-refs",
+		maintenance_task_prune_remote,
+	},
 };
 
 static int compare_tasks_by_selection(const void *a_, const void *b_)
@@ -1505,6 +1545,8 @@  static void initialize_maintenance_strategy(void)
 		tasks[TASK_LOOSE_OBJECTS].schedule = SCHEDULE_DAILY;
 		tasks[TASK_PACK_REFS].enabled = 1;
 		tasks[TASK_PACK_REFS].schedule = SCHEDULE_WEEKLY;
+		tasks[TASK_PRUNE_REMOTE_REFS].enabled = 0;
+		tasks[TASK_PRUNE_REMOTE_REFS].schedule = SCHEDULE_DAILY;
 	}
 }
 
diff --git a/t/t7900-maintenance.sh b/t/t7900-maintenance.sh
index 0ce4ba1cbef..60a0c3f8353 100755
--- a/t/t7900-maintenance.sh
+++ b/t/t7900-maintenance.sh
@@ -446,6 +446,50 @@  test_expect_success 'pack-refs task' '
 	test_subcommand git pack-refs --all --prune <pack-refs.txt
 '
 
+test_expect_success 'prune-remote-refs task not enabled by default' '
+	git clone . prune-test &&
+	(
+		cd prune-test &&
+		GIT_TRACE2_EVENT="$(pwd)/prune.txt" git maintenance run 2>err &&
+		test_subcommand ! git remote prune origin <prune.txt
+	)
+'
+
+test_expect_success 'prune-remote-refs task cleans stale remote refs' '
+	test_commit initial &&
+
+	# Create two separate remote repos
+	git clone . remote1 &&
+	git clone . remote2 &&
+
+	git clone . prune-test-clean &&
+	(
+		cd prune-test-clean &&
+		git config maintenance.prune-remote-refs.enabled true &&
+
+		# Add both remotes
+		git remote add remote1 "../remote1" &&
+		git remote add remote2 "../remote2" &&
+
+		# Create and push branches to both remotes
+		git branch -f side2 HEAD &&
+		git push remote1 side2 &&
+		git push remote2 side2 &&
+
+		# Rename branches in each remote to simulate a stale branch
+		git -C ../remote1 branch -m side2 side3 &&
+		git -C ../remote2 branch -m side2 side4 &&
+
+		GIT_TRACE2_EVENT="$(pwd)/prune.txt" git maintenance run --task=prune-remote-refs &&
+
+		# Verify pruning happened for both remotes
+		test_subcommand git remote prune remote1 <prune.txt &&
+		test_subcommand git remote prune remote2 <prune.txt &&
+		test_must_fail git rev-parse refs/remotes/remote1/side2 &&
+		test_must_fail git rev-parse refs/remotes/remote2/side2
+	)
+'
+
 test_expect_success '--auto and --schedule incompatible' '
 	test_must_fail git maintenance run --auto --schedule=daily 2>err &&
 	test_grep "at most one" err