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[PATCH 08/15] job-runner: create builtin for job loop

From
Derrick Stolee via GitGitGadget <gitgitgadget@gmail.com>
Date
Apr 3, 2020, 20:48 UTC
Message-ID
<90379bad303e77cc82ef79fc2ba505805a571483.1585946894.git.gitgitgadget@gmail.com>
In-Reply-To
<pull.597.git.1585946894.gitgitgadget@gmail.com>
From: Derrick Stolee <dstolee@microsoft.com>

Given the existing 'git run-job <job-name>' builtin, users _could_ construct their own scheduling mechanism for running jobs in the background. However, it is much easier to have a dedicated process that manages all jobs across multiple repos.

The 'git job-runner' builtin is specifically built to handle this scenario. It will be customized further in later changes, but for now it does the following:

* Given a list of '--repo=<path>' arguments, construct a list of
  repositories to manage with jobs.
* Every 30 minutes, iterate over all jobs and all repos to run
	git -C <repo> run-job <job-name>

This builtin needs to be careful about how much of the Git internals it consumes. The intention is that this is a long-lived process that could be launched upon login and only closed on logout. For that reason, we will avoid instantiating any object store or index data.

Run the maintenance jobs by running subcommands. We will update how we enable or disable these jobs and separate their runs in a later change.

RFC QUESTIONS:
1. The hardest part of this builtin is "how do we test it?" In
   Scalar, we can unit test the scheduler with mocks. What is the
   equivalent here for "make sure 'git job-runner' runs 'git run-job
   pack-files' on repo X? I expect to add a "--no-loop" option that
   ensures the logic only runs one iteration of the loop.
2. The difference between 'git run-job' and 'git job-runner' is
   subtle and probably confusing. Are there better names?
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 .gitignore                       |   1 +
 Documentation/git-job-runner.txt |  52 +++++++++++++++
 Makefile                         |   1 +
 builtin.h                        |   1 +
 builtin/job-runner.c             | 111 +++++++++++++++++++++++++++++++
 command-list.txt                 |   1 +
 git.c                            |   1 +
 7 files changed, 168 insertions(+)
 create mode 100644 Documentation/git-job-runner.txt
 create mode 100644 builtin/job-runner.c
diff --git a/.gitignore b/.gitignore
index 5dea9d3b96b..24c377b2883 100644
--- a/.gitignore
+++ b/.gitignore
@@ -83,6 +83,7 @@
 /git-init-db
 /git-interpret-trailers
 /git-instaweb
+/git-job-runner
 /git-log
 /git-ls-files
 /git-ls-remote
diff --git a/Documentation/git-job-runner.txt b/Documentation/git-job-runner.txt
new file mode 100644
index 00000000000..010b2d05f9b
--- /dev/null
+++ b/Documentation/git-job-runner.txt
@@ -0,0 +1,52 @@
+git-job-runner(1)
+=================
+
+NAME
+----
+git-job-runner - run jobs on multiple repos according to a schedlue.
+Intended for background operation.
+
+
+SYNOPSIS
+--------
+[verse]
+'git job-runner [--repo=<path>]'
+
+
+DESCRIPTION
+-----------
+
+Run jobs in a loop with some frequency. Intended for running in the
+background.
+
+The `git run-job <job-name>` command runs a specific maintenance task.
+The `job-runner` command is a long-running process that calls the
+`run-job` command on a set of repositories at some frequency. The
+`job.*` config values customize the frequencies of these jobs.
+
+
+OPTIONS
+-------
+
+--repo=<dir>::
+	If at least one `--repo` option is provided, the runner only
+	attempts running jobs on repositories located at the provided
+	`<dir>` values. This option can be specified multiple times.
+
+
+CONFIGURATION
+-------------
+
+The `git job-runner` command is intended to run as a long-running
+process. The following config options are checked periodically during
+the process and will modify its behavior:
+
+The below documentation is the same as what's found in
+linkgit:git-config[1]:
+
+include::config/job.txt[]
+
+
+GIT
+---
+Part of the linkgit:git[1] suite
diff --git a/Makefile b/Makefile
index f5f9c4d9e94..ee98a91af0f 100644
--- a/Makefile
+++ b/Makefile
@@ -1082,6 +1082,7 @@ BUILTIN_OBJS += builtin/help.o
 BUILTIN_OBJS += builtin/index-pack.o
 BUILTIN_OBJS += builtin/init-db.o
 BUILTIN_OBJS += builtin/interpret-trailers.o
+BUILTIN_OBJS += builtin/job-runner.o
 BUILTIN_OBJS += builtin/log.o
 BUILTIN_OBJS += builtin/ls-files.o
 BUILTIN_OBJS += builtin/ls-remote.o
diff --git a/builtin.h b/builtin.h
index 3e0ddaaf67f..5008c7096b3 100644
--- a/builtin.h
+++ b/builtin.h
@@ -176,6 +176,7 @@ int cmd_help(int argc, const char **argv, const char *prefix);
 int cmd_index_pack(int argc, const char **argv, const char *prefix);
 int cmd_init_db(int argc, const char **argv, const char *prefix);
 int cmd_interpret_trailers(int argc, const char **argv, const char *prefix);
+int cmd_job_runner(int argc, const char **argv, const char *prefix);
 int cmd_log(int argc, const char **argv, const char *prefix);
 int cmd_log_reflog(int argc, const char **argv, const char *prefix);
 int cmd_ls_files(int argc, const char **argv, const char *prefix);
diff --git a/builtin/job-runner.c b/builtin/job-runner.c
new file mode 100644
index 00000000000..135288bcaae
--- /dev/null
+++ b/builtin/job-runner.c
@@ -0,0 +1,111 @@
+#include "builtin.h"
+#include "config.h"
+#include "parse-options.h"
+#include "run-command.h"
+#include "string-list.h"
+
+static char const * const builtin_job_runner_usage[] = {
+	N_("git job-runner [<options>]"),
+	NULL
+};
+
+static struct string_list arg_repos = STRING_LIST_INIT_DUP;
+
+static int arg_repos_append(const struct option *opt,
+			    const char *arg, int unset)
+{
+	string_list_append(&arg_repos, arg);
+	return 0;
+}
+
+static int load_active_repos(struct string_list *repos)
+{
+	if (arg_repos.nr) {
+		struct string_list_item *item;
+		for (item = arg_repos.items;
+		     item && item < arg_repos.items + arg_repos.nr;
+		     item++)
+			string_list_append(repos, item->string);
+		return 0;
+	}
+
+	return 0;
+}
+
+static int run_job(const char *job, const char *repo)
+{
+	struct argv_array cmd = ARGV_ARRAY_INIT;
+	argv_array_pushl(&cmd, "-C", repo, "run-job", job, NULL);
+	return run_command_v_opt(cmd.argv, RUN_GIT_CMD);
+}
+
+static int run_job_loop_step(struct string_list *list)
+{
+	int result = 0;
+	struct string_list_item *job;
+	struct string_list repos = STRING_LIST_INIT_DUP;
+
+	if ((result = load_active_repos(&repos)))
+		return result;
+
+	for (job = list->items;
+	     !result && job && job < list->items + list->nr;
+	     job++) {
+		struct string_list_item *repo;
+		for (repo = repos.items;
+		     !result && repo && repo < repos.items + repos.nr;
+		     repo++)
+			result = run_job(job->string,
+					 repo->string);
+	}
+
+	string_list_clear(&repos, 0);
+	return result;
+}
+
+static unsigned int get_loop_interval(void)
+{
+	/* Default: 30 minutes */
+	return 30 * 60;
+}
+
+static int initialize_jobs(struct string_list *list)
+{
+	string_list_append(list, "commit-graph");
+	string_list_append(list, "fetch");
+	string_list_append(list, "loose-objects");
+	string_list_append(list, "pack-files");
+	return 0;
+}
+
+int cmd_job_runner(int argc, const char **argv, const char *prefix)
+{
+	int result;
+	struct string_list job_list = STRING_LIST_INIT_DUP;
+	static struct option builtin_job_runner_options[] = {
+		OPT_CALLBACK_F(0, "repo",
+			       NULL,
+			       N_("<path>"),
+			       N_("run jobs on the repository at <path>"),
+			       PARSE_OPT_NONEG, arg_repos_append),
+		OPT_END(),
+	};
+
+	if (argc == 2 && !strcmp(argv[1], "-h"))
+		usage_with_options(builtin_job_runner_usage,
+				   builtin_job_runner_options);
+
+	argc = parse_options(argc, argv, prefix,
+			     builtin_job_runner_options,
+			     builtin_job_runner_usage,
+			     0);
+
+	result = initialize_jobs(&job_list);
+
+	while (!(result = run_job_loop_step(&job_list))) {
+		unsigned int interval = get_loop_interval();
+		sleep(interval);
+	}
+
+	return result;
+}
diff --git a/command-list.txt b/command-list.txt
index 1cd2b415e46..cb835c74693 100644
--- a/command-list.txt
+++ b/command-list.txt
@@ -110,6 +110,7 @@ git-init                                mainporcelain           init
 git-instaweb                            ancillaryinterrogators          complete
 git-interpret-trailers                  purehelpers
 gitk                                    mainporcelain
+git-job-runner                          plumbingmanipulators
 git-log                                 mainporcelain           info
 git-ls-files                            plumbinginterrogators
 git-ls-remote                           plumbinginterrogators
diff --git a/git.c b/git.c
index db5a43c8687..3a2da2c232f 100644
--- a/git.c
+++ b/git.c
@@ -517,6 +517,7 @@ static struct cmd_struct commands[] = {
 	{ "init", cmd_init_db },
 	{ "init-db", cmd_init_db },
 	{ "interpret-trailers", cmd_interpret_trailers, RUN_SETUP_GENTLY },
+	{ "job-runner", cmd_job_runner, RUN_SETUP_GENTLY },
 	{ "log", cmd_log, RUN_SETUP },
 	{ "ls-files", cmd_ls_files, RUN_SETUP },
 	{ "ls-remote", cmd_ls_remote, RUN_SETUP_GENTLY },

-- 
gitgitgadget
Previous: Derrick StoleeNext: Derrick Stolee via GitGitGadget
Message 28 of 55 in “[RFC] Maintenance jobs and job runner”
  1. 00/15 [RFC] Maintenance jobs and job runnerDerrick Stolee via GitGitGadget, Apr 3, 2020
  2. 01/15 run-job: create barebones builtinDerrick Stolee via GitGitGadget, Apr 3, 2020
  3. Phillip WoodApr 5, 2020
  4. Junio C HamanoApr 5, 2020
  5. Derrick StoleeApr 6, 2020
  6. Danh DoanApr 7, 2020
  7. Derrick StoleeApr 7, 2020
  8. Danh DoanApr 7, 2020
  9. Johannes SchindelinApr 7, 2020
  10. 02/15 run-job: implement commit-graph jobDerrick Stolee via GitGitGadget, Apr 3, 2020
  11. Josh SteadmonMay 20, 2020
  12. 05/15 run-job: implement pack-files jobDerrick Stolee via GitGitGadget, Apr 3, 2020
  13. Josh SteadmonMay 27, 2020
  14. 03/15 run-job: implement fetch jobDerrick Stolee via GitGitGadget, Apr 3, 2020
  15. Phillip WoodApr 5, 2020
  16. Derrick StoleeApr 6, 2020
  17. Junio C HamanoApr 5, 2020
  18. Derrick StoleeApr 6, 2020
  19. Josh SteadmonMay 20, 2020
  20. 06/15 run-job: auto-size or use custom pack-files batchDerrick Stolee via GitGitGadget, Apr 3, 2020
  21. 04/15 run-job: implement loose-objects jobDerrick Stolee via GitGitGadget, Apr 3, 2020
  22. Junio C HamanoApr 5, 2020
  23. 09/15 job-runner: load repos from config by defaultDerrick Stolee via GitGitGadget, Apr 3, 2020
  24. Phillip WoodApr 5, 2020
  25. Derrick StoleeApr 6, 2020
  26. Phillip WoodApr 5, 2020
  27. Derrick StoleeApr 6, 2020
  28. 08/15 job-runner: create builtin for job loopDerrick Stolee via GitGitGadget, Apr 3, 2020
  29. 11/15 job-runner: use config for loop intervalDerrick Stolee via GitGitGadget, Apr 3, 2020
  30. 10/15 job-runner: use config to limit job frequencyDerrick Stolee via GitGitGadget, Apr 3, 2020
  31. Phillip WoodApr 5, 2020
  32. 13/15 job-runner: skip a job if job.<job-name>.enabled is falseDerrick Stolee via GitGitGadget, Apr 3, 2020
  33. 14/15 job-runner: add --daemonize optionDerrick Stolee via GitGitGadget, Apr 3, 2020
  34. 12/15 job-runner: add --interval=<span> optionDerrick Stolee via GitGitGadget, Apr 3, 2020
  35. 07/15 config: add job.pack-files.batchSize optionDerrick Stolee via GitGitGadget, Apr 3, 2020
  36. 15/15 runjob: customize the loose-objects batch sizeDerrick Stolee via GitGitGadget, Apr 3, 2020
  37. Junio C HamanoApr 3, 2020
  38. Derrick StoleeApr 4, 2020
  39. Danh DoanApr 7, 2020
  40. Derrick StoleeApr 7, 2020
  41. Danh DoanApr 7, 2020
  42. Johannes SchindelinApr 7, 2020
  43. brian m. carlsonApr 7, 2020
  44. Junio C HamanoApr 7, 2020
  45. Johannes SchindelinApr 7, 2020
  46. brian m. carlsonApr 8, 2020
  47. Josh SteadmonMay 27, 2020
  48. Junio C HamanoMay 28, 2020
  49. Johannes SchindelinMay 27, 2020
  50. Junio C HamanoMay 28, 2020
  51. Jonathan NiederMay 28, 2020
  52. Junio C HamanoMay 28, 2020
  53. Jonathan NiederMay 28, 2020
  54. Derrick StoleeMay 28, 2020
  55. Johannes SchindelinMay 28, 2020

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