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From: "Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com>
To: git@vger.kernel.org
Cc: jrnieder@gmail.com, jonathantanmy@google.com, sluongng@gmail.com,
	congdanhqx@gmail.com, Derrick Stolee <derrickstolee@github.com>,
	Derrick Stolee <dstolee@microsoft.com>
Subject: [PATCH 5/7] maintenance: add start/stop subcommands
Date: Fri, 04 Sep 2020 15:42:04 +0000	[thread overview]
Message-ID: <e02641881d998d1e6a31e941b61eb6f89d0519f7.1599234127.git.gitgitgadget@gmail.com> (raw)
In-Reply-To: <pull.724.git.1599234126.gitgitgadget@gmail.com>

From: Derrick Stolee <dstolee@microsoft.com>

Add new subcommands to 'git maintenance' that start or stop background
maintenance using 'cron', when available. This integration is as simple
as I could make it, barring some implementation complications.

The schedule is laid out as follows:

  0 1-23 * * *   $cmd maintenance run --schedule=hourly
  0 0    * * 1-6 $cmd maintenance run --schedule=daily
  0 0    * * 0   $cmd maintenance run --schedule=weekly

where $cmd is a properly-qualified 'git for-each-repo' execution:

$cmd=$path/git --exec-path=$path for-each-repo --config=maintenance.repo

where $path points to the location of the Git executable running 'git
maintenance start'. This is critical for systems with multiple versions
of Git. Specifically, macOS has a system version at '/usr/bin/git' while
the version that users can install resides at '/usr/local/bin/git'
(symlinked to '/usr/local/libexec/git-core/git'). This will also use
your locally-built version if you build and run this in your development
environment without installing first.

This conditional schedule avoids having cron launch multiple 'git
for-each-repo' commands in parallel. Such parallel commands would likely
lead to the 'hourly' and 'daily' tasks competing over the object
database lock. This could lead to to some tasks never being run! Since
the --schedule=<frequency> argument will run all tasks with _at least_
the given frequency, the daily runs will also run the hourly tasks.
Similarly, the weekly runs will also run the daily and hourly tasks.

The GIT_TEST_CRONTAB environment variable is not intended for users to
edit, but instead as a way to mock the 'crontab [-l]' command. This
variable is set in test-lib.sh to avoid a future test from accidentally
running anything with the cron integration from modifying the user's
schedule. We use GIT_TEST_CRONTAB='test-tool crontab <file>' in our
tests to check how the schedule is modified in 'git maintenance
(start|stop)' commands.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 Documentation/git-maintenance.txt |  11 +++
 Makefile                          |   1 +
 builtin/gc.c                      | 124 ++++++++++++++++++++++++++++++
 t/helper/test-crontab.c           |  35 +++++++++
 t/helper/test-tool.c              |   1 +
 t/helper/test-tool.h              |   1 +
 t/t7900-maintenance.sh            |  28 +++++++
 t/test-lib.sh                     |   6 ++
 8 files changed, 207 insertions(+)
 create mode 100644 t/helper/test-crontab.c

diff --git a/Documentation/git-maintenance.txt b/Documentation/git-maintenance.txt
index 78d0d8df91..7f8c279fe8 100644
--- a/Documentation/git-maintenance.txt
+++ b/Documentation/git-maintenance.txt
@@ -45,6 +45,17 @@ run::
 	config options are true. By default, only `maintenance.gc.enabled`
 	is true.
 
+start::
+	Start running maintenance on the current repository. This performs
+	the same config updates as the `register` subcommand, then updates
+	the background scheduler to run `git maintenance run --scheduled`
+	on an hourly basis.
+
+stop::
+	Halt the background maintenance schedule. The current repository
+	is not removed from the list of maintained repositories, in case
+	the background maintenance is restarted later.
+
 unregister::
 	Remove the current repository from background maintenance. This
 	only removes the repository from the configured list. It does not
diff --git a/Makefile b/Makefile
index 7c588ff036..c39b39bd7d 100644
--- a/Makefile
+++ b/Makefile
@@ -690,6 +690,7 @@ TEST_BUILTINS_OBJS += test-advise.o
 TEST_BUILTINS_OBJS += test-bloom.o
 TEST_BUILTINS_OBJS += test-chmtime.o
 TEST_BUILTINS_OBJS += test-config.o
+TEST_BUILTINS_OBJS += test-crontab.o
 TEST_BUILTINS_OBJS += test-ctype.o
 TEST_BUILTINS_OBJS += test-date.o
 TEST_BUILTINS_OBJS += test-delta.o
diff --git a/builtin/gc.c b/builtin/gc.c
index ec77e8d2fa..9914417e25 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -32,6 +32,7 @@
 #include "remote.h"
 #include "midx.h"
 #include "object-store.h"
+#include "exec-cmd.h"
 
 #define FAILED_RUN "failed to run %s"
 
@@ -1456,6 +1457,125 @@ static int maintenance_unregister(void)
 	return run_command(&config_unset);
 }
 
+#define BEGIN_LINE "# BEGIN GIT MAINTENANCE SCHEDULE"
+#define END_LINE "# END GIT MAINTENANCE SCHEDULE"
+
+static int update_background_schedule(int run_maintenance)
+{
+	int result = 0;
+	int in_old_region = 0;
+	struct child_process crontab_list = CHILD_PROCESS_INIT;
+	struct child_process crontab_edit = CHILD_PROCESS_INIT;
+	FILE *cron_list, *cron_in;
+	const char *crontab_name;
+	struct strbuf line = STRBUF_INIT;
+	struct lock_file lk;
+	char *lock_path = xstrfmt("%s/schedule", the_repository->objects->odb->path);
+
+	if (hold_lock_file_for_update(&lk, lock_path, LOCK_NO_DEREF) < 0)
+		return error(_("another process is scheduling background maintenance"));
+
+	crontab_name = getenv("GIT_TEST_CRONTAB");
+	if (!crontab_name)
+		crontab_name = "crontab";
+
+	strvec_split(&crontab_list.args, crontab_name);
+	strvec_push(&crontab_list.args, "-l");
+	crontab_list.in = -1;
+	crontab_list.out = dup(lk.tempfile->fd);
+	crontab_list.git_cmd = 0;
+
+	if (start_command(&crontab_list)) {
+		result = error(_("failed to run 'crontab -l'; your system might not support 'cron'"));
+		goto cleanup;
+	}
+
+	/* Ignore exit code, as an empty crontab will return error. */
+	finish_command(&crontab_list);
+
+	/*
+	 * Read from the .lock file, filtering out the old
+	 * schedule while appending the new schedule.
+	 */
+	cron_list = fdopen(lk.tempfile->fd, "r");
+	rewind(cron_list);
+
+	strvec_split(&crontab_edit.args, crontab_name);
+	crontab_edit.in = -1;
+	crontab_edit.git_cmd = 0;
+
+	if (start_command(&crontab_edit)) {
+		result = error(_("failed to run 'crontab'; your system might not support 'cron'"));
+		goto cleanup;
+	}
+
+	cron_in = fdopen(crontab_edit.in, "w");
+	if (!cron_in) {
+		result = error(_("failed to open stdin of 'crontab'"));
+		goto done_editing;
+	}
+
+	while (!strbuf_getline_lf(&line, cron_list)) {
+		if (!in_old_region && !strcmp(line.buf, BEGIN_LINE))
+			in_old_region = 1;
+		if (in_old_region)
+			continue;
+		fprintf(cron_in, "%s\n", line.buf);
+		if (in_old_region && !strcmp(line.buf, END_LINE))
+			in_old_region = 0;
+	}
+
+	if (run_maintenance) {
+		struct strbuf line_format = STRBUF_INIT;
+		const char *exec_path = git_exec_path();
+
+		fprintf(cron_in, "%s\n", BEGIN_LINE);
+		fprintf(cron_in,
+			"# The following schedule was created by Git\n");
+		fprintf(cron_in, "# Any edits made in this region might be\n");
+		fprintf(cron_in,
+			"# replaced in the future by a Git command.\n\n");
+
+		strbuf_addf(&line_format,
+			    "%%s %%s * * %%s \"%s/git\" --exec-path=\"%s\" for-each-repo --config=maintenance.repo maintenance run --schedule=%%s\n",
+			    exec_path, exec_path);
+		fprintf(cron_in, line_format.buf, "0", "1-23", "*", "hourly");
+		fprintf(cron_in, line_format.buf, "0", "0", "1-6", "daily");
+		fprintf(cron_in, line_format.buf, "0", "0", "0", "weekly");
+		strbuf_release(&line_format);
+
+		fprintf(cron_in, "\n%s\n", END_LINE);
+	}
+
+	fflush(cron_in);
+	fclose(cron_in);
+	close(crontab_edit.in);
+
+done_editing:
+	if (finish_command(&crontab_edit)) {
+		result = error(_("'crontab' died"));
+		goto cleanup;
+	}
+	fclose(cron_list);
+
+cleanup:
+	rollback_lock_file(&lk);
+	return result;
+}
+
+static int maintenance_start(void)
+{
+	if (maintenance_register())
+		warning(_("failed to add repo to global config"));
+
+	return update_background_schedule(1);
+}
+
+static int maintenance_stop(void)
+{
+	return update_background_schedule(0);
+}
+
 static const char builtin_maintenance_usage[] =	N_("git maintenance <subcommand> [<options>]");
 
 int cmd_maintenance(int argc, const char **argv, const char *prefix)
@@ -1465,6 +1585,10 @@ int cmd_maintenance(int argc, const char **argv, const char *prefix)
 
 	if (!strcmp(argv[1], "run"))
 		return maintenance_run(argc - 1, argv + 1, prefix);
+	if (!strcmp(argv[1], "start"))
+		return maintenance_start();
+	if (!strcmp(argv[1], "stop"))
+		return maintenance_stop();
 	if (!strcmp(argv[1], "register"))
 		return maintenance_register();
 	if (!strcmp(argv[1], "unregister"))
diff --git a/t/helper/test-crontab.c b/t/helper/test-crontab.c
new file mode 100644
index 0000000000..f5db6319c6
--- /dev/null
+++ b/t/helper/test-crontab.c
@@ -0,0 +1,35 @@
+#include "test-tool.h"
+#include "cache.h"
+
+/*
+ * Usage: test-tool cron <file> [-l]
+ *
+ * If -l is specified, then write the contents of <file> to stdou.
+ * Otherwise, write from stdin into <file>.
+ */
+int cmd__crontab(int argc, const char **argv)
+{
+	char a;
+	FILE *from, *to;
+
+	if (argc == 3 && !strcmp(argv[2], "-l")) {
+		from = fopen(argv[1], "r");
+		if (!from)
+			return 0;
+		to = stdout;
+	} else if (argc == 2) {
+		from = stdin;
+		to = fopen(argv[1], "w");
+	} else
+		return error("unknown arguments");
+
+	while ((a = fgetc(from)) != EOF)
+		fputc(a, to);
+
+	if (argc == 3)
+		fclose(from);
+	else
+		fclose(to);
+
+	return 0;
+}
diff --git a/t/helper/test-tool.c b/t/helper/test-tool.c
index 590b2efca7..432b49d948 100644
--- a/t/helper/test-tool.c
+++ b/t/helper/test-tool.c
@@ -18,6 +18,7 @@ static struct test_cmd cmds[] = {
 	{ "bloom", cmd__bloom },
 	{ "chmtime", cmd__chmtime },
 	{ "config", cmd__config },
+	{ "crontab", cmd__crontab },
 	{ "ctype", cmd__ctype },
 	{ "date", cmd__date },
 	{ "delta", cmd__delta },
diff --git a/t/helper/test-tool.h b/t/helper/test-tool.h
index ddc8e990e9..7c3281e071 100644
--- a/t/helper/test-tool.h
+++ b/t/helper/test-tool.h
@@ -8,6 +8,7 @@ int cmd__advise_if_enabled(int argc, const char **argv);
 int cmd__bloom(int argc, const char **argv);
 int cmd__chmtime(int argc, const char **argv);
 int cmd__config(int argc, const char **argv);
+int cmd__crontab(int argc, const char **argv);
 int cmd__ctype(int argc, const char **argv);
 int cmd__date(int argc, const char **argv);
 int cmd__delta(int argc, const char **argv);
diff --git a/t/t7900-maintenance.sh b/t/t7900-maintenance.sh
index 272d1605d2..8803fcf621 100755
--- a/t/t7900-maintenance.sh
+++ b/t/t7900-maintenance.sh
@@ -319,4 +319,32 @@ test_expect_success 'register and unregister' '
 	test_cmp before actual
 '
 
+test_expect_success 'start from empty cron table' '
+	GIT_TEST_CRONTAB="test-tool crontab cron.txt" git maintenance start &&
+
+	# start registers the repo
+	git config --get --global maintenance.repo "$(pwd)" &&
+
+	grep "for-each-repo --config=maintenance.repo maintenance run --schedule=daily" cron.txt &&
+	grep "for-each-repo --config=maintenance.repo maintenance run --schedule=hourly" cron.txt &&
+	grep "for-each-repo --config=maintenance.repo maintenance run --schedule=weekly" cron.txt
+'
+
+test_expect_success 'stop from existing schedule' '
+	GIT_TEST_CRONTAB="test-tool crontab cron.txt" git maintenance stop &&
+
+	# stop does not unregister the repo
+	git config --get --global maintenance.repo "$(pwd)" &&
+
+	# Operation is idempotent
+	GIT_TEST_CRONTAB="test-tool crontab cron.txt" git maintenance stop &&
+	test_must_be_empty cron.txt
+'
+
+test_expect_success 'start preserves existing schedule' '
+	echo "Important information!" >cron.txt &&
+	GIT_TEST_CRONTAB="test-tool crontab cron.txt" git maintenance start &&
+	grep "Important information!" cron.txt
+'
+
 test_done
diff --git a/t/test-lib.sh b/t/test-lib.sh
index ef31f40037..4a60d1ed76 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -1702,3 +1702,9 @@ test_lazy_prereq SHA1 '
 test_lazy_prereq REBASE_P '
 	test -z "$GIT_TEST_SKIP_REBASE_P"
 '
+
+# Ensure that no test accidentally triggers a Git command
+# that runs 'crontab', affecting a user's cron schedule.
+# Tests that verify the cron integration must set this locally
+# to avoid errors.
+GIT_TEST_CRONTAB="exit 1"
-- 
gitgitgadget


  parent reply	other threads:[~2020-09-04 15:43 UTC|newest]

Thread overview: 62+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-04 15:41 [PATCH 0/7] Maintenance III: Background maintenance Derrick Stolee via GitGitGadget
2020-09-04 15:42 ` [PATCH 1/7] maintenance: optionally skip --auto process Derrick Stolee via GitGitGadget
2020-09-04 15:42 ` [PATCH 2/7] maintenance: add --schedule option and config Derrick Stolee via GitGitGadget
2020-09-08 13:07   ` Đoàn Trần Công Danh
2020-09-09 12:14     ` Derrick Stolee
2020-09-04 15:42 ` [PATCH 3/7] for-each-repo: run subcommands on configured repos Derrick Stolee via GitGitGadget
2020-09-04 15:42 ` [PATCH 4/7] maintenance: add [un]register subcommands Derrick Stolee via GitGitGadget
2020-09-04 15:42 ` Derrick Stolee via GitGitGadget [this message]
2020-09-08  6:29   ` [PATCH 5/7] maintenance: add start/stop subcommands SZEDER Gábor
2020-09-08 12:43     ` Derrick Stolee
2020-09-08 19:31     ` Junio C Hamano
2020-09-04 15:42 ` [PATCH 6/7] maintenance: recommended schedule in register/start Derrick Stolee via GitGitGadget
2020-09-04 15:42 ` [PATCH 7/7] maintenance: add troubleshooting guide to docs Derrick Stolee via GitGitGadget
2020-09-11 17:49 ` [PATCH v2 0/7] Maintenance III: Background maintenance Derrick Stolee via GitGitGadget
2020-09-11 17:49   ` [PATCH v2 1/7] maintenance: optionally skip --auto process Derrick Stolee via GitGitGadget
2020-09-11 17:49   ` [PATCH v2 2/7] maintenance: add --schedule option and config Derrick Stolee via GitGitGadget
2020-09-11 17:49   ` [PATCH v2 3/7] for-each-repo: run subcommands on configured repos Derrick Stolee via GitGitGadget
2020-09-11 17:49   ` [PATCH v2 4/7] maintenance: add [un]register subcommands Derrick Stolee via GitGitGadget
2020-09-17 14:05     ` Đoàn Trần Công Danh
2020-09-11 17:49   ` [PATCH v2 5/7] maintenance: add start/stop subcommands Derrick Stolee via GitGitGadget
2020-09-11 17:49   ` [PATCH v2 6/7] maintenance: recommended schedule in register/start Derrick Stolee via GitGitGadget
2020-09-29 19:48     ` Martin Ågren
2020-09-30 20:11       ` Derrick Stolee
2020-10-01 20:38         ` Derrick Stolee
2020-10-02  0:38           ` Đoàn Trần Công Danh
2020-10-02  1:55             ` Derrick Stolee
2020-10-05 13:16               ` Đoàn Trần Công Danh
2020-10-05 18:17                 ` Derrick Stolee
2020-09-11 17:49   ` [PATCH v2 7/7] maintenance: add troubleshooting guide to docs Derrick Stolee via GitGitGadget
2020-10-05 12:57   ` [PATCH v3 0/7] Maintenance III: Background maintenance Derrick Stolee via GitGitGadget
2020-10-05 12:57     ` [PATCH v3 1/7] maintenance: optionally skip --auto process Derrick Stolee via GitGitGadget
2020-10-05 12:57     ` [PATCH v3 2/7] maintenance: add --schedule option and config Derrick Stolee via GitGitGadget
2020-10-05 12:57     ` [PATCH v3 3/7] for-each-repo: run subcommands on configured repos Derrick Stolee via GitGitGadget
2020-10-05 12:57     ` [PATCH v3 4/7] maintenance: add [un]register subcommands Derrick Stolee via GitGitGadget
2020-10-05 12:57     ` [PATCH v3 5/7] maintenance: add start/stop subcommands Derrick Stolee via GitGitGadget
2020-10-05 12:57     ` [PATCH v3 6/7] maintenance: use default schedule if not configured Derrick Stolee via GitGitGadget
2020-10-05 19:57       ` Martin Ågren
2020-10-08 13:32         ` Derrick Stolee
2020-10-05 12:57     ` [PATCH v3 7/7] maintenance: add troubleshooting guide to docs Derrick Stolee via GitGitGadget
2020-10-15 17:21     ` [PATCH v4 0/8] Maintenance III: Background maintenance Derrick Stolee via GitGitGadget
2020-10-15 17:21       ` [PATCH v4 1/8] maintenance: optionally skip --auto process Derrick Stolee via GitGitGadget
2020-10-15 17:21       ` [PATCH v4 2/8] maintenance: add --schedule option and config Derrick Stolee via GitGitGadget
2021-02-09 14:06         ` Ævar Arnfjörð Bjarmason
2021-02-09 16:54           ` Derrick Stolee
2021-05-10 12:16             ` Ævar Arnfjörð Bjarmason
2021-05-10 18:42               ` Junio C Hamano
2020-10-15 17:21       ` [PATCH v4 3/8] for-each-repo: run subcommands on configured repos Derrick Stolee via GitGitGadget
2021-05-03 16:10         ` Andrzej Hunt
2021-05-03 17:01           ` Eric Sunshine
2021-05-03 19:26             ` Eric Sunshine
2021-05-03 19:43           ` Derrick Stolee
2020-10-15 17:22       ` [PATCH v4 4/8] maintenance: add [un]register subcommands Derrick Stolee via GitGitGadget
2020-10-15 17:22       ` [PATCH v4 5/8] maintenance: add start/stop subcommands Derrick Stolee via GitGitGadget
2020-12-09 18:51         ` Josh Steadmon
2020-12-09 19:16           ` Josh Steadmon
2020-12-09 21:59             ` Derrick Stolee
2020-12-10  0:13             ` Junio C Hamano
2020-12-10  1:52               ` Derrick Stolee
2020-12-10  6:54                 ` Junio C Hamano
2020-10-15 17:22       ` [PATCH v4 6/8] maintenance: create maintenance.strategy config Derrick Stolee via GitGitGadget
2020-10-15 17:22       ` [PATCH v4 7/8] maintenance: use 'incremental' strategy by default Derrick Stolee via GitGitGadget
2020-10-15 17:22       ` [PATCH v4 8/8] maintenance: add troubleshooting guide to docs Derrick Stolee via GitGitGadget

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