repmgrd: create pid file by default

Traditionally repmgrd will only write a pidfile if explicitly requested with
-p/--pid-file. However it's normally desirable to have a pidfile, and it's
preferable to have one used by default to prevent accidentally starting a second
repmgrd instance.

Following changes made:

 - add configuration file parameter "repmgrd_pid_file" (initially overridden by
   -p/--pid-file for backwards compatibility, though eventually we'll want to
   drop -p/--pid-file altogether)
 - add command line option --no-pid-file
 - if neither "repmgrd_pid_file" nor -p/--pid-file is set, create the pid file
   in a temporary directory

Implements GitHub #457.

configfile.c

@@ -359,6 +359,7 @@ _parse_config(t_configuration_options *options, ItemList *error_list, ItemList *
 	options->async_query_timeout = DEFAULT_ASYNC_QUERY_TIMEOUT;
 	options->primary_notification_timeout = DEFAULT_PRIMARY_NOTIFICATION_TIMEOUT;
 	options->repmgrd_standby_startup_timeout = -1; /* defaults to "standby_reconnect_timeout" if not set */
+	memset(options->repmgrd_pid_file, 0, sizeof(options->repmgrd_pid_file));
 
 	/*-------------
 	 * witness settings
@@ -604,6 +605,8 @@ _parse_config(t_configuration_options *options, ItemList *error_list, ItemList *
 			options->primary_notification_timeout = repmgr_atoi(value, name, error_list, 0);
 		else if (strcmp(name, "repmgrd_standby_startup_timeout") == 0)
 			options->repmgrd_standby_startup_timeout = repmgr_atoi(value, name, error_list, 0);
+		else if (strcmp(name, "repmgrd_pid_file") == 0)
+			strncpy(options->repmgrd_pid_file, value, MAXPGPATH);
 
 		/* witness settings */
 		else if (strcmp(name, "witness_sync_interval") == 0)

configfile.h

@@ -131,6 +131,7 @@ typedef struct
 	int			async_query_timeout;
 	int			primary_notification_timeout;
 	int			repmgrd_standby_startup_timeout;
+	char		repmgrd_pid_file[MAXPGPATH];
 
 	/* BDR settings */
 	bool		bdr_local_monitoring_only;
@@ -196,7 +197,7 @@ typedef struct
         false, -1, \
 		DEFAULT_ASYNC_QUERY_TIMEOUT, \
 		DEFAULT_PRIMARY_NOTIFICATION_TIMEOUT,	\
-		-1,	\
+		-1, "", \
 		/* BDR settings */ \
 		false, DEFAULT_BDR_RECOVERY_TIMEOUT, \
 		/* service settings */ \

repmgr.conf.sample

@@ -258,6 +258,11 @@ ssh_options='-q -o ConnectTimeout=10'	# Options to append to "ssh"
 # These settings are only applied when repmgrd is running. Values shown
 # are defaults.
 
+#repmgrd_pid_file=			# Path of PID file to use for repmgrd; if not set, a PID file will
+                                        # be generated in a temporary directory specified by the environment
+                                        # variable $TMPDIR, or if not set, in "/tmp". This value can be overridden
+                                        # by the command line option "-p/--pid-file"; the command line option
+                                        # "--no-pid-file" will force PID file creation to be skipped.
 #failover=manual			# one of 'automatic', 'manual'.
 					# determines what action to take in the event of upstream failure
 					#

repmgrd.c

@@ -35,8 +35,10 @@
 
 static char *config_file = NULL;
 static bool verbose = false;
-static char *pid_file = NULL;
+static char pid_file[MAXPGPATH];
 static bool daemonize = false;
+static bool show_pid_file = false;
+static bool no_pid_file = false;
 
 t_configuration_options config_file_options = T_CONFIGURATION_OPTIONS_INITIALIZER;
 
@@ -101,6 +103,8 @@ main(int argc, char **argv)
 /* daemon options */
 		{"daemonize", no_argument, NULL, 'd'},
 		{"pid-file", required_argument, NULL, 'p'},
+		{"show-pid-file", no_argument, NULL, 's'},
+		{"no-pid-file", no_argument, NULL, OPT_NO_PID_FILE},
 
 /* logging options */
 		{"log-level", required_argument, NULL, 'L'},
@@ -113,8 +117,6 @@ main(int argc, char **argv)
 
 	set_progname(argv[0]);
 
-	srand(time(NULL));
-
 	/* Disallow running as root */
 	if (geteuid() == 0)
 	{
@@ -128,6 +130,10 @@ main(int argc, char **argv)
 		exit(1);
 	}
 
+	srand(time(NULL));
+
+	memset(pid_file, 0, MAXPGPATH);
+
 	while ((c = getopt_long(argc, argv, "?Vf:L:vdp:m", long_options, &optindex)) != -1)
 	{
 		switch (c)
@@ -173,7 +179,15 @@ main(int argc, char **argv)
 				break;
 
 			case 'p':
-				pid_file = optarg;
+				strncpy(pid_file, optarg, MAXPGPATH);
+				break;
+
+			case 's':
+				show_pid_file = true;
+				break;
+
+			case OPT_NO_PID_FILE:
+				no_pid_file = true;
 				break;
 
 				/* logging options */
@@ -239,6 +253,48 @@ main(int argc, char **argv)
 	 */
 	load_config(config_file, verbose, false, &config_file_options, argv[0]);
 
+	/* Determine pid file location, unless --no-pid-file supplied */
+
+	if (no_pid_file == false)
+	{
+		if (config_file_options.repmgrd_pid_file[0] != '\0')
+		{
+			if (pid_file[0] != '\0')
+			{
+				log_warning(_("\"repmgrd_pid_file\" will be overridden by --pid-file"));
+			}
+			else
+			{
+				strncpy(pid_file, config_file_options.repmgrd_pid_file, MAXPGPATH);
+			}
+		}
+
+		/* no pid file provided - determine location */
+		if (pid_file[0] == '\0')
+		{
+			const char *tmpdir = getenv("TMPDIR");
+
+			if (!tmpdir)
+				tmpdir = "/tmp";
+
+			maxpath_snprintf(pid_file, "%s/repmgrd.pid", tmpdir);
+		}
+	}
+	else
+	{
+		/* --no-pid-file supplied - overwrite any value provided with --pid-file ... */
+		memset(pid_file, 0, MAXPGPATH);
+	}
+
+
+	/* If --show-pid-file supplied, output the location (if set) and exit */
+
+	if (show_pid_file == true)
+	{
+		printf("%s\n", pid_file);
+		exit(SUCCESS);
+	}
+
 
 	/* Some configuration file items can be overriden by command line options */
 
@@ -414,7 +470,7 @@ main(int argc, char **argv)
 		daemonize_process();
 	}
 
-	if (pid_file != NULL)
+	if (pid_file[0] != '\0')
 	{
 		check_and_create_pid_file(pid_file);
 	}
@@ -669,6 +725,8 @@ show_help(void)
 {
 	printf(_("%s: replication management daemon for PostgreSQL\n"), progname());
 	puts("");
+	printf(_("%s monitors a cluster of servers and optionally performs failover.\n"), progname());
+	puts("");
 
 	printf(_("Usage:\n"));
 	printf(_("  %s [OPTIONS]\n"), progname());
@@ -688,12 +746,13 @@ show_help(void)
 
 	puts("");
 
-	printf(_("General configuration options:\n"));
+	printf(_("Daemon configuration options:\n"));
 	printf(_("  -d, --daemonize           detach process from foreground\n"));
-	printf(_("  -p, --pid-file=PATH       write a PID file\n"));
+	printf(_("  -p, --pid-file=PATH       use the specified PID file\n"));
+	printf(_("  -s, --show-pid-file       show PID file which would be used by the current configuration\n"));
+	printf(_("  --no-pid-file             don't write a PID file\n"));
 	puts("");
 
-	printf(_("%s monitors a cluster of servers and optionally performs failover.\n"), progname());
 }
 
 
@@ -802,7 +861,7 @@ terminate(int retval)
 {
 	logger_shutdown();
 
-	if (pid_file)
+	if (pid_file[0] != '\0')
 	{
 		unlink(pid_file);
 	}

repmgrd.h

@@ -10,6 +10,8 @@
 #include <time.h>
 #include "portability/instr_time.h"
 
+#define OPT_NO_PID_FILE                  1000
+
 extern volatile sig_atomic_t got_SIGHUP;
 extern MonitoringState monitoring_state;
 extern instr_time degraded_monitoring_start;
@@ -26,4 +28,6 @@ const char *print_monitoring_state(MonitoringState monitoring_state);
 
 void		update_registration(PGconn *conn);
 void		terminate(int retval);
+
+
 #endif							/* _REPMGRD_H_ */