Add support for systemd service notifications

Insert sd_notify() calls at server start and stop for integration with
systemd.  This allows the use of systemd service units of type "notify",
which greatly simplifies the systemd configuration.

Reviewed-by: Pavel Stěhule <pavel.stehule@gmail.com>

4 files changed, 34 insertions, 0 deletions

diff --git a/src/Makefile.global.in b/src/Makefile.global.in
index 51f479713c3..e94d6a58a0c 100644
--- a/src/Makefile.global.in
+++ b/src/Makefile.global.in
@@ -184,6 +184,7 @@ with_python	= @with_python@
 with_tcl	= @with_tcl@
 with_openssl	= @with_openssl@
 with_selinux	= @with_selinux@
+with_systemd	= @with_systemd@
 with_libxml	= @with_libxml@
 with_libxslt	= @with_libxslt@
 with_system_tzdata = @with_system_tzdata@
diff --git a/src/backend/Makefile b/src/backend/Makefile
index d4db8ff57a2..b3d5e2e1bd9 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -45,6 +45,10 @@ LIBS := $(filter-out -lpgport -lpgcommon, $(LIBS)) $(LDAP_LIBS_BE)
 # The backend doesn't need everything that's in LIBS, however
 LIBS := $(filter-out -lz -lreadline -ledit -ltermcap -lncurses -lcurses, $(LIBS))
 
+ifeq ($(with_systemd),yes)
+LIBS += -lsystemd
+endif
+
 ##########################################################################
 
 all: submake-libpgport submake-schemapg postgres $(POSTGRES_IMP)
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index 9aaed5b9848..d983a50ee1d 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -87,6 +87,10 @@
 #include <dns_sd.h>
 #endif
 
+#ifdef USE_SYSTEMD
+#include <systemd/sd-daemon.h>
+#endif
+
 #ifdef HAVE_PTHREAD_IS_THREADED_NP
 #include <pthread.h>
 #endif
@@ -2533,6 +2537,9 @@ pmdie(SIGNAL_ARGS)
 			Shutdown = SmartShutdown;
 			ereport(LOG,
 					(errmsg("received smart shutdown request")));
+#ifdef USE_SYSTEMD
+			sd_notify(0, "STOPPING=1");
+#endif
 
 			if (pmState == PM_RUN || pmState == PM_RECOVERY ||
 				pmState == PM_HOT_STANDBY || pmState == PM_STARTUP)
@@ -2585,6 +2592,9 @@ pmdie(SIGNAL_ARGS)
 			Shutdown = FastShutdown;
 			ereport(LOG,
 					(errmsg("received fast shutdown request")));
+#ifdef USE_SYSTEMD
+			sd_notify(0, "STOPPING=1");
+#endif
 
 			if (StartupPID != 0)
 				signal_child(StartupPID, SIGTERM);
@@ -2645,6 +2655,9 @@ pmdie(SIGNAL_ARGS)
 			Shutdown = ImmediateShutdown;
 			ereport(LOG,
 					(errmsg("received immediate shutdown request")));
+#ifdef USE_SYSTEMD
+			sd_notify(0, "STOPPING=1");
+#endif
 
 			TerminateChildren(SIGQUIT);
 			pmState = PM_WAIT_BACKENDS;
@@ -2787,6 +2800,10 @@ reaper(SIGNAL_ARGS)
 			ereport(LOG,
 				 (errmsg("database system is ready to accept connections")));
 
+#ifdef USE_SYSTEMD
+			sd_notify(0, "READY=1");
+#endif
+
 			continue;
 		}
 
@@ -4916,6 +4933,11 @@ sigusr1_handler(SIGNAL_ARGS)
 		if (XLogArchivingAlways())
 			PgArchPID = pgarch_start();
 
+#ifdef USE_SYSTEMD
+		if (!EnableHotStandby)
+			sd_notify(0, "READY=1");
+#endif
+
 		pmState = PM_RECOVERY;
 	}
 	if (CheckPostmasterSignal(PMSIGNAL_BEGIN_HOT_STANDBY) &&
@@ -4930,6 +4952,10 @@ sigusr1_handler(SIGNAL_ARGS)
 		ereport(LOG,
 		(errmsg("database system is ready to accept read only connections")));
 
+#ifdef USE_SYSTEMD
+		sd_notify(0, "READY=1");
+#endif
+
 		pmState = PM_HOT_STANDBY;
 		/* Some workers may be scheduled to start now */
 		StartWorkerNeeded = true;
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index 16a272efdee..b3ceea5edc9 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -833,6 +833,9 @@
 /* Define to 1 to use Intel SSSE 4.2 CRC instructions with a runtime check. */
 #undef USE_SSE42_CRC32C_WITH_RUNTIME_CHECK
 
+/* Define to build with systemd support. (--with-systemd) */
+#undef USE_SYSTEMD
+
 /* Define to select SysV-style semaphores. */
 #undef USE_SYSV_SEMAPHORES