git/list[1] front-page[2] threads[3] people[4] search[5] about
 

[PATCH v4] daemon: add --log-destination=(stderr|syslog|none)

From
Lucas Werkmeister <mail@lucaswerkmeister.de>
Date
Feb 4, 2018, 18:30 UTC
Message-ID
<20180204183037.23162-1-mail@lucaswerkmeister.de>
In-Reply-To
<772ae5fc-5f92-3494-613a-a44c0073e8d7@lucaswerkmeister.de>

This new option can be used to override the implicit --syslog of --inetd, or to disable all logging. (While --detach also implies --syslog, --log-destination=stderr with --detach is useless since --detach disassociates the process from the original stderr.) --syslog is retained as an alias for --log-destination=syslog.

--log-destination always overrides implicit --syslog regardless of option order. This is different than the “last one wins” logic that applies to some implicit options elsewhere in Git, but should hopefully be less confusing. (I also don’t know if *all* implicit options in Git follow “last one wins”.)

The combination of --inetd with --log-destination=stderr is useful, for instance, when running `git daemon` as an instanced systemd service (with associated socket unit). In this case, log messages sent via syslog are received by the journal daemon, but run the risk of being processed at a time when the `git daemon` process has already exited (especially if the process was very short-lived, e.g. due to client error), so that the journal daemon can no longer read its cgroup and attach the message to the correct systemd unit (see systemd/systemd#2913 [1]). Logging to stderr instead can solve this problem, because systemd can connect stderr directly to the journal daemon, which then already knows which unit is associated with this stream.

[1]: https://github.com/systemd/systemd/issues/2913
Helped-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Helped-by: Junio C Hamano <gitster@pobox.com>
Helped-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Lucas Werkmeister <mail@lucaswerkmeister.de>
---
Notes:
    Fixes log_destination not being initialized correctly and some minor
    style issues.
 Documentation/git-daemon.txt | 28 ++++++++++++++++++++++++---
 daemon.c                     | 46 +++++++++++++++++++++++++++++++++++++-------
 2 files changed, 64 insertions(+), 10 deletions(-)
diff --git a/Documentation/git-daemon.txt b/Documentation/git-daemon.txt
index 3c91db7be..56d54a489 100644
--- a/Documentation/git-daemon.txt
+++ b/Documentation/git-daemon.txt
@@ -20,6 +20,7 @@ SYNOPSIS
 	     [--inetd |
 	      [--listen=<host_or_ipaddr>] [--port=<n>]
 	      [--user=<user> [--group=<group>]]]
+	     [--log-destination=(stderr|syslog|none)]
 	     [<directory>...]
 
 DESCRIPTION
@@ -80,7 +81,8 @@ OPTIONS
 	do not have the 'git-daemon-export-ok' file.
 
 --inetd::
-	Have the server run as an inetd service. Implies --syslog.
+	Have the server run as an inetd service. Implies --syslog (may be
+	overridden with `--log-destination=`).
 	Incompatible with --detach, --port, --listen, --user and --group
 	options.
 
@@ -110,8 +112,28 @@ OPTIONS
 	zero for no limit.
 
 --syslog::
-	Log to syslog instead of stderr. Note that this option does not imply
-	--verbose, thus by default only error conditions will be logged.
+	Short for `--log-destination=syslog`.
+
+--log-destination=<destination>::
+	Send log messages to the specified destination.
+	Note that this option does not imply --verbose,
+	thus by default only error conditions will be logged.
+	The <destination> must be one of:
++
+--
+stderr::
+	Write to standard error.
+	Note that if `--detach` is specified,
+	the process disconnects from the real standard error,
+	making this destination effectively equivalent to `none`.
+syslog::
+	Write to syslog, using the `git-daemon` identifier.
+none::
+	Disable all logging.
+--
++
+The default destination is `syslog` if `--inetd` or `--detach` is specified,
+otherwise `stderr`.
 
 --user-path::
 --user-path=<path>::
diff --git a/daemon.c b/daemon.c
index e37e343d0..fb538e367 100644
--- a/daemon.c
+++ b/daemon.c
@@ -9,7 +9,12 @@
 #define initgroups(x, y) (0) /* nothing */
 #endif
 
-static int log_syslog;
+static enum log_destination {
+	LOG_DESTINATION_UNSET = -1,
+	LOG_DESTINATION_NONE = 0,
+	LOG_DESTINATION_STDERR = 1,
+	LOG_DESTINATION_SYSLOG = 2,
+} log_destination = LOG_DESTINATION_UNSET;
 static int verbose;
 static int reuseaddr;
 static int informative_errors;
@@ -25,6 +30,7 @@ static const char daemon_usage[] =
 "           [--access-hook=<path>]\n"
 "           [--inetd | [--listen=<host_or_ipaddr>] [--port=<n>]\n"
 "                      [--detach] [--user=<user> [--group=<group>]]\n"
+"           [--log-destination=(stderr|syslog|none)]\n"
 "           [<directory>...]";
 
 /* List of acceptable pathname prefixes */
@@ -74,11 +80,14 @@ static const char *get_ip_address(struct hostinfo *hi)
 
 static void logreport(int priority, const char *err, va_list params)
 {
-	if (log_syslog) {
+	switch (log_destination) {
+	case LOG_DESTINATION_SYSLOG: {
 		char buf[1024];
 		vsnprintf(buf, sizeof(buf), err, params);
 		syslog(priority, "%s", buf);
-	} else {
+		break;
+	}
+	case LOG_DESTINATION_STDERR:
 		/*
 		 * Since stderr is set to buffered mode, the
 		 * logging of different processes will not overlap
@@ -88,6 +97,11 @@ static void logreport(int priority, const char *err, va_list params)
 		vfprintf(stderr, err, params);
 		fputc('\n', stderr);
 		fflush(stderr);
+		break;
+	case LOG_DESTINATION_NONE:
+		break;
+	case LOG_DESTINATION_UNSET:
+		BUG("log destination not initialized correctly");
 	}
 }
 
@@ -1289,7 +1303,6 @@ int cmd_main(int argc, const char **argv)
 		}
 		if (!strcmp(arg, "--inetd")) {
 			inetd_mode = 1;
-			log_syslog = 1;
 			continue;
 		}
 		if (!strcmp(arg, "--verbose")) {
@@ -1297,9 +1310,22 @@ int cmd_main(int argc, const char **argv)
 			continue;
 		}
 		if (!strcmp(arg, "--syslog")) {
-			log_syslog = 1;
+			log_destination = LOG_DESTINATION_SYSLOG;
 			continue;
 		}
+		if (skip_prefix(arg, "--log-destination=", &v)) {
+			if (!strcmp(v, "syslog")) {
+				log_destination = LOG_DESTINATION_SYSLOG;
+				continue;
+			} else if (!strcmp(v, "stderr")) {
+				log_destination = LOG_DESTINATION_STDERR;
+				continue;
+			} else if (!strcmp(v, "none")) {
+				log_destination = LOG_DESTINATION_NONE;
+				continue;
+			} else
+				die("unknown log destination '%s'", v);
+		}
 		if (!strcmp(arg, "--export-all")) {
 			export_all_trees = 1;
 			continue;
@@ -1356,7 +1382,6 @@ int cmd_main(int argc, const char **argv)
 		}
 		if (!strcmp(arg, "--detach")) {
 			detach = 1;
-			log_syslog = 1;
 			continue;
 		}
 		if (skip_prefix(arg, "--user=", &v)) {
@@ -1402,7 +1427,14 @@ int cmd_main(int argc, const char **argv)
 		usage(daemon_usage);
 	}
 
-	if (log_syslog) {
+	if (log_destination == LOG_DESTINATION_UNSET) {
+		if (inetd_mode || detach)
+			log_destination = LOG_DESTINATION_SYSLOG;
+		else
+			log_destination = LOG_DESTINATION_STDERR;
+	}
+
+	if (log_destination == LOG_DESTINATION_SYSLOG) {
 		openlog("git-daemon", LOG_PID, LOG_DAEMON);
 		set_die_routine(daemon_die);
 	} else

-- 
2.16.1
Previous: Lucas WerkmeisterNext: Ævar Arnfjörð Bjarmason
Message 15 of 21 in “daemon: add --no-syslog to undo implicit --syslog”
  1. daemon: add --no-syslog to undo implicit --syslogLucas Werkmeister, Jan 22, 2018
  2. Ævar Arnfjörð BjarmasonJan 23, 2018
  3. Junio C HamanoJan 23, 2018
  4. Lucas WerkmeisterJan 23, 2018
  5. Lucas WerkmeisterJan 24, 2018
  6. Junio C HamanoJan 24, 2018
  7. Lucas WerkmeisterJan 24, 2018
  8. daemon: add --send-log-to=(stderr|syslog|none)Lucas Werkmeister, Jan 27, 2018
  9. Eric SunshineJan 28, 2018
  10. Lucas WerkmeisterJan 28, 2018
  11. Eric SunshineJan 29, 2018
  12. daemon: add --log-destination=(stderr|syslog|none)Lucas Werkmeister, Feb 3, 2018
  13. Eric SunshineFeb 4, 2018
  14. Lucas WerkmeisterFeb 4, 2018
  15. daemon: add --log-destination=(stderr|syslog|none)Lucas Werkmeister, Feb 4, 2018
  16. Ævar Arnfjörð BjarmasonFeb 4, 2018
  17. Lucas WerkmeisterFeb 4, 2018
  18. Ævar Arnfjörð BjarmasonFeb 5, 2018
  19. Eric SunshineFeb 4, 2018
  20. Eric SunshineFeb 4, 2018
  21. Junio C HamanoFeb 5, 2018

Read the whole thread, see it on lore, or plain text.

$ cat FOOTERMessages come from the public archive at lore.kernel.org/git, fetched every hour. The front page is chosen and written each morning by an AI editor and can be wrong; the threads themselves are the record. About and API. For agents: an MCP server at https://gitlist.dev/mcp, and any thread, story or person page as Markdown by adding .md to its URL (or sending Accept: text/markdown). Details in /llms.txt.