gc: remove gc.pid file at end of execution

PATCH In review Matthieu Moy 4 participants 5 messages Jun 15, 2016

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Matthieu Moy

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2016-06-15 22:58 UTC #0 lore raw

PATCH 1/1 gc: remove gc.pid file at end of execution

This file isn't really harmful, but isn't useful either, and can create minor annoyance for the user:

* It's confusing, as the presence of a *.pid file often implies that a process is currently running. A user running "ls .git/" and finding this file may incorrectly guess that a "git gc" is currently running.

* Leaving this file means that a "git gc" in an already gc-ed repo is no-longer a no-op. A user running "git gc" in a set of repositories, and then synchronizing this set (e.g. rsync -av, unison, ...) will see all the gc.pid files as changed, which creates useless noise.

This patch unlinks the file after the garbage collection is done, so that gc.pid is actually present only during execution.

Future versions of Git may want to use the information left in the gc.pid file (e.g. for policies like "don't attempt to run a gc if one has already been ran less than X hours ago"). If so, this patch can safely be reverted. For now, let's not bother the users.

Signed-off-by Matthieu Moy <[email protected]>

---
 builtin/gc.c | 4 ++++
 1 file changed, 4 insertions(+)

builtin/gc.c +4 -0

index 891a2c2..db39963 100644
@@ -316,5 +316,9 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
 		warning(_("There are too many unreachable loose objects; "
 			"run 'git prune' to remove them."));
 
+	/*
+	 * The file isn't harmful, but isn't useful either.
+	 */
+	unlink(git_path("gc.pid"));
 	return 0;
 }

Signature · 1 line

1.8.4.474.g128a96c

Jonathan Nieder

2016-06-15 22:58 UTC #1 lore raw

Quoted 2 lines · Matthieu Moy

This file isn't really harmful, but isn't useful either, and can create minor annoyance for the user:

Would something like the following make sense, to ensure the gc.pid file is always removed on normal exit?

Signed-off-by Jonathan Nieder <[email protected]>

builtin/gc.c +28 -2

index 6e0d81a..fbbc144 100644
@@ -14,6 +14,7 @@
 #include "cache.h"
 #include "parse-options.h"
 #include "run-command.h"
+#include "sigchain.h"
 #include "argv-array.h"
 
 #define FAILED_RUN "failed to run %s"

@@ -167,6 +168,21 @@ static int need_to_gc(void)
 	return 1;
 }
 
+static char *pidfile;
+
+static void remove_pidfile(void)
+{
+	if (pidfile)
+		unlink(pidfile);
+}
+
+static void remove_pidfile_on_signal(int signo)
+{
+	remove_pidfile();
+	sigchain_pop(signo);
+	raise(signo);
+}
+
 /* return NULL on success, else hostname running the gc */
 static const char *lock_repo_for_gc(int force, pid_t* ret_pid)
 {

@@ -179,13 +195,19 @@ static const char *lock_repo_for_gc(int force, pid_t* ret_pid)
 	FILE *fp;
 	int fd, should_exit;
 
+	if (pidfile)
+		/* already locked */
+		return NULL;
+
 	if (gethostname(my_host, sizeof(my_host)))
 		strcpy(my_host, "unknown");
 
-	fd = hold_lock_file_for_update(&lock, git_path("gc.pid"),
+	pidfile = git_pathdup("gc.pid");
+
+	fd = hold_lock_file_for_update(&lock, pidfile,
 				       LOCK_DIE_ON_ERROR);
 	if (!force) {
-		fp = fopen(git_path("gc.pid"), "r");
+		fp = fopen(pidfile, "r");
 		memset(locking_host, 0, sizeof(locking_host));
 		should_exit =
 			fp != NULL &&

@@ -208,6 +230,7 @@ static const char *lock_repo_for_gc(int force, pid_t* ret_pid)
 		if (should_exit) {
 			if (fd >= 0)
 				rollback_lock_file(&lock);
+			pidfile = NULL;
 			*ret_pid = pid;
 			return locking_host;
 		}

@@ -219,6 +242,9 @@ static const char *lock_repo_for_gc(int force, pid_t* ret_pid)
 	strbuf_release(&sb);
 	commit_lock_file(&lock);
 
+	sigchain_push_common(remove_pidfile_on_signal);
+	atexit(remove_pidfile);
+
 	return NULL;
 }

Duy Nguyen

2016-06-15 22:58 UTC #2 lore raw

Quoted 75 lines · Jonathan Nieder

Quoted 2 lines · Matthieu Moy

This file isn't really harmful, but isn't useful either, and can create minor annoyance for the user:

Would something like the following make sense, to ensure the gc.pid file is always removed on normal exit?

Signed-off-by Jonathan Nieder <[email protected]>

builtin/gc.c +25 -2

index 6e0d81a..fbbc144 100644
@@ -14,6 +14,7 @@
 #include "cache.h"
 #include "parse-options.h"
 #include "run-command.h"
+#include "sigchain.h"
 #include "argv-array.h"
 
 #define FAILED_RUN "failed to run %s"

@@ -167,6 +168,21 @@ static int need_to_gc(void)
        return 1;
 }
 
+static char *pidfile;
+
+static void remove_pidfile(void)
+{
+       if (pidfile)
+               unlink(pidfile);
+}
+
+static void remove_pidfile_on_signal(int signo)
+{
+       remove_pidfile();
+       sigchain_pop(signo);
+       raise(signo);
+}
+
 /* return NULL on success, else hostname running the gc */
 static const char *lock_repo_for_gc(int force, pid_t* ret_pid)
 {

@@ -179,13 +195,19 @@ static const char *lock_repo_for_gc(int force, pid_t* ret_pid)
        FILE *fp;
        int fd, should_exit;
 
+       if (pidfile)
+               /* already locked */
+               return NULL;
+
        if (gethostname(my_host, sizeof(my_host)))
                strcpy(my_host, "unknown");
 
-       fd = hold_lock_file_for_update(&lock, git_path("gc.pid"),
+       pidfile = git_pathdup("gc.pid");
+
+       fd = hold_lock_file_for_update(&lock, pidfile,
                                       LOCK_DIE_ON_ERROR);
        if (!force) {
-               fp = fopen(git_path("gc.pid"), "r");
+               fp = fopen(pidfile, "r");
                memset(locking_host, 0, sizeof(locking_host));
                should_exit =
                        fp != NULL &&

@@ -208,6 +230,7 @@ static const char *lock_repo_for_gc(int force, pid_t* ret_pid)
                if (should_exit) {
                        if (fd >= 0)
                                rollback_lock_file(&lock);
+                       pidfile = NULL;
                        *ret_pid = pid;
                        return locking_host;
                }

builtin/gc.c static const char *lock_repo_for_gc(int force, pid_t* ret_pid) · line 242

Quoted 1 line

builtin/gc.c +0 -0

@@ -219,6 +242,9 @@ static const char *lock_repo_for_gc(int force, pid_t* ret_pid)
        strbuf_release(&sb);

It may be a bit simpler to delay setting pidfile until we get here. lock.filename still contains gc.pid until commit_lock_file is called.

Quoted 7 lines

builtin/gc.c +3 -0

        commit_lock_file(&lock);
 
+       sigchain_push_common(remove_pidfile_on_signal);
+       atexit(remove_pidfile);
+
        return NULL;
 }

Signature · 1 line

Duy

Junio C Hamano

2016-06-15 22:59 UTC #3 lore raw

In reply to Jonathan Nieder

Quoted 7 lines · Jonathan Nieder

Quoted 2 lines · Matthieu Moy
This file isn't really harmful, but isn't useful either, and can create minor annoyance for the user:
Would something like the following make sense, to ensure the gc.pid file is always removed on normal exit?

Has anything further happened to this discussion?

Jonathan Nieder

2016-06-15 22:59 UTC #4 lore raw

PATCH v2 1/1 gc: remove gc.pid file at end of execution

This file isn't really harmful, but isn't useful either, and can create minor annoyance for the user:

This patch unlinks the file after the garbage collection is done, so that gc.pid is actually present only during execution.

Explained-by Matthieu Moy <[email protected]>

Signed-off-by Jonathan Nieder <[email protected]>

Improved-by Nguyễn Thái Ngọc Duy <[email protected]>

---

Quoted 1 line · Junio C Hamano

Has anything further happened to this discussion?

Here's a patch implementing Duy's suggestion.

 builtin/gc.c  | 24 ++++++++++++++++++++++++
 t/t6500-gc.sh |  5 +++++
 2 files changed, 29 insertions(+)

builtin/gc.c +24 -0

index 891a2c2..c14190f 100644
@@ -14,6 +14,7 @@
 #include "cache.h"
 #include "parse-options.h"
 #include "run-command.h"
+#include "sigchain.h"
 #include "argv-array.h"
 
 #define FAILED_RUN "failed to run %s"

@@ -35,6 +36,21 @@ static struct argv_array repack = ARGV_ARRAY_INIT;
 static struct argv_array prune = ARGV_ARRAY_INIT;
 static struct argv_array rerere = ARGV_ARRAY_INIT;
 
+static char *pidfile;
+
+static void remove_pidfile(void)
+{
+	if (pidfile)
+		unlink(pidfile);
+}
+
+static void remove_pidfile_on_signal(int signo)
+{
+	remove_pidfile();
+	sigchain_pop(signo);
+	raise(signo);
+}
+
 static int gc_config(const char *var, const char *value, void *cb)
 {
 	if (!strcmp(var, "gc.packrefs")) {

@@ -179,6 +195,10 @@ static const char *lock_repo_for_gc(int force, pid_t* ret_pid)
 	FILE *fp;
 	int fd, should_exit;
 
+	if (pidfile)
+		/* already locked */
+		return NULL;
+
 	if (gethostname(my_host, sizeof(my_host)))
 		strcpy(my_host, "unknown");

@@ -219,6 +239,10 @@ static const char *lock_repo_for_gc(int force, pid_t* ret_pid)
 	strbuf_release(&sb);
 	commit_lock_file(&lock);
 
+	pidfile = git_pathdup("gc.pid");
+	sigchain_push_common(remove_pidfile_on_signal);
+	atexit(remove_pidfile);
+
 	return NULL;
 }

t/t6500-gc.sh +5 -0

index b1a6365..63194d8 100755
@@ -9,6 +9,11 @@ test_expect_success 'gc empty repository' '
 	git gc
 '
 
+test_expect_success 'gc does not leave behind pid file' '
+	git gc &&
+	test_path_is_missing .git/gc.pid
+'
+
 test_expect_success 'gc --gobbledegook' '
 	test_expect_code 129 git gc --nonsense 2>err &&
 	test_i18ngrep "[Uu]sage: git gc" err

Signature · 1 line

1.8.4-50-g437ce60