[PATCH v2 4/8] maintenance: use random minute in cron scheduler

From: Derrick Stolee via GitGitGadget <gitgitgadget@gmail.com>
Date: Aug 10, 2023, 20:39 UTC
Message-ID: <b291e6f7aec3a651f9366fac8eea0903f939d767.1691699987.git.gitgitgadget@gmail.com>
In-Reply-To: <pull.1567.v2.git.1691699987.gitgitgadget@gmail.com>

From: Derrick Stolee <derrickstolee@github.com>

The get_random_minute() method was created to allow maintenance schedules to be fixed to a random minute of the hour. This randomness is only intended to spread out the load from a number of clients, but each client should have an hour between each maintenance cycle.

Add this random minute to the cron integration.

The cron schedule specification starts with a minute indicator, which was previously inserted as the "0" string but now takes the given minute as an integer parameter.

Signed-off-by: Derrick Stolee <derrickstolee@github.com>
---
 builtin/gc.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/builtin/gc.c b/builtin/gc.c
index 78924bb32c6..ef8bb772c38 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -2174,6 +2174,7 @@ static int crontab_update_schedule(int run_maintenance, int fd)
 	FILE *cron_list, *cron_in;
 	struct strbuf line = STRBUF_INIT;
 	struct tempfile *tmpedit = NULL;
+	int minute = get_random_minute();
 
 	get_schedule_cmd(&cmd, NULL);
 	strvec_split(&crontab_list.args, cmd);
@@ -2228,11 +2229,11 @@ static int crontab_update_schedule(int run_maintenance, int fd)
 			"# 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",
+			    "%%d %%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");
+		fprintf(cron_in, line_format.buf, minute, "1-23", "*", "hourly");
+		fprintf(cron_in, line_format.buf, minute, "0", "1-6", "daily");
+		fprintf(cron_in, line_format.buf, minute, "0", "0", "weekly");
 		strbuf_release(&line_format);
 
 		fprintf(cron_in, "\n%s\n", END_LINE);

-- 
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