Unify several ways to tracking backend type

Add a new global variable MyBackendType that uses the same BackendType
enum that was previously only used by the stats collector.  That way
several duplicate ways of checking what type a particular process is
can be simplified.  Since it's no longer just for stats, move to
miscinit.c and rename existing functions to match the expanded
purpose.
Reviewed-by: Julien Rouhaud <rjuju123@gmail.com>
Reviewed-by: Kuntal Ghosh <kuntalghosh.2007@gmail.com>
Reviewed-by: Alvaro Herrera <alvherre@2ndquadrant.com>
Discussion: https://www.postgresql.org/message-id/flat/c65e5196-4f04-4ead-9353-6088c19615a3@2ndquadrant.com

src/backend/bootstrap/bootstrap.c

@@ -314,36 +314,28 @@ AuxiliaryProcessMain(int argc, char *argv[])
 		proc_exit(1);
 	}
 
-	/*
-	 * Identify myself via ps
-	 */
-	if (IsUnderPostmaster)
-	{
-		const char *statmsg;
-
 	switch (MyAuxProcType)
 	{
 		case StartupProcess:
-				statmsg = pgstat_get_backend_desc(B_STARTUP);
+			MyBackendType = B_STARTUP;
 			break;
 		case BgWriterProcess:
-				statmsg = pgstat_get_backend_desc(B_BG_WRITER);
+			MyBackendType = B_BG_WRITER;
 			break;
 		case CheckpointerProcess:
-				statmsg = pgstat_get_backend_desc(B_CHECKPOINTER);
+			MyBackendType = B_CHECKPOINTER;
 			break;
 		case WalWriterProcess:
-				statmsg = pgstat_get_backend_desc(B_WAL_WRITER);
+			MyBackendType = B_WAL_WRITER;
 			break;
 		case WalReceiverProcess:
-				statmsg = pgstat_get_backend_desc(B_WAL_RECEIVER);
+			MyBackendType = B_WAL_RECEIVER;
 			break;
 		default:
-				statmsg = "??? process";
-				break;
-		}
-		init_ps_display(statmsg);
+			MyBackendType = B_INVALID;
 	}
+	if (IsUnderPostmaster)
+		init_ps_display(NULL);
 
 	/* Acquire configuration parameters, unless inherited from postmaster */
 	if (!IsUnderPostmaster)

src/backend/postmaster/autovacuum.c

@@ -433,8 +433,8 @@ AutoVacLauncherMain(int argc, char *argv[])
 
 	am_autovacuum_launcher = true;
 
-	/* Identify myself via ps */
-	init_ps_display(pgstat_get_backend_desc(B_AUTOVAC_LAUNCHER));
+	MyBackendType = B_AUTOVAC_LAUNCHER;
+	init_ps_display(NULL);
 
 	ereport(DEBUG1,
 			(errmsg("autovacuum launcher started")));
@@ -1506,8 +1506,8 @@ AutoVacWorkerMain(int argc, char *argv[])
 
 	am_autovacuum_worker = true;
 
-	/* Identify myself via ps */
-	init_ps_display(pgstat_get_backend_desc(B_AUTOVAC_WORKER));
+	MyBackendType = B_AUTOVAC_WORKER;
+	init_ps_display(NULL);
 
 	SetProcessingMode(InitProcessing);
 

src/backend/postmaster/bgworker.c

@@ -688,7 +688,7 @@ StartBackgroundWorker(void)
 
 	IsBackgroundWorker = true;
 
-	/* Identify myself via ps */
+	MyBackendType = B_BG_WORKER;
 	init_ps_display(worker->bgw_name);
 
 	/*

src/backend/postmaster/pgarch.c

@@ -238,10 +238,8 @@ PgArchiverMain(int argc, char *argv[])
 	pqsignal(SIGCHLD, SIG_DFL);
 	PG_SETMASK(&UnBlockSig);
 
-	/*
-	 * Identify myself via ps
-	 */
-	init_ps_display("archiver");
+	MyBackendType = B_ARCHIVER;
+	init_ps_display(NULL);
 
 	pgarch_MainLoop();
 

src/backend/postmaster/pgstat.c

@@ -2892,62 +2892,7 @@ pgstat_bestart(void)
 	 * out-of-line data.  Those have to be handled separately, below.
 	 */
 	lbeentry.st_procpid = MyProcPid;
-
-	if (MyBackendId != InvalidBackendId)
-	{
-		if (IsAutoVacuumLauncherProcess())
-		{
-			/* Autovacuum Launcher */
-			lbeentry.st_backendType = B_AUTOVAC_LAUNCHER;
-		}
-		else if (IsAutoVacuumWorkerProcess())
-		{
-			/* Autovacuum Worker */
-			lbeentry.st_backendType = B_AUTOVAC_WORKER;
-		}
-		else if (am_walsender)
-		{
-			/* Wal sender */
-			lbeentry.st_backendType = B_WAL_SENDER;
-		}
-		else if (IsBackgroundWorker)
-		{
-			/* bgworker */
-			lbeentry.st_backendType = B_BG_WORKER;
-		}
-		else
-		{
-			/* client-backend */
-			lbeentry.st_backendType = B_BACKEND;
-		}
-	}
-	else
-	{
-		/* Must be an auxiliary process */
-		Assert(MyAuxProcType != NotAnAuxProcess);
-		switch (MyAuxProcType)
-		{
-			case StartupProcess:
-				lbeentry.st_backendType = B_STARTUP;
-				break;
-			case BgWriterProcess:
-				lbeentry.st_backendType = B_BG_WRITER;
-				break;
-			case CheckpointerProcess:
-				lbeentry.st_backendType = B_CHECKPOINTER;
-				break;
-			case WalWriterProcess:
-				lbeentry.st_backendType = B_WAL_WRITER;
-				break;
-			case WalReceiverProcess:
-				lbeentry.st_backendType = B_WAL_RECEIVER;
-				break;
-			default:
-				elog(FATAL, "unrecognized process type: %d",
-					 (int) MyAuxProcType);
-		}
-	}
-
+	lbeentry.st_backendType = MyBackendType;
 	lbeentry.st_proc_start_timestamp = MyStartTimestamp;
 	lbeentry.st_activity_start_timestamp = 0;
 	lbeentry.st_state_start_timestamp = 0;
@@ -4269,48 +4214,6 @@ pgstat_get_crashed_backend_activity(int pid, char *buffer, int buflen)
 	return NULL;
 }
 
-const char *
-pgstat_get_backend_desc(BackendType backendType)
-{
-	const char *backendDesc = "unknown process type";
-
-	switch (backendType)
-	{
-		case B_AUTOVAC_LAUNCHER:
-			backendDesc = "autovacuum launcher";
-			break;
-		case B_AUTOVAC_WORKER:
-			backendDesc = "autovacuum worker";
-			break;
-		case B_BACKEND:
-			backendDesc = "client backend";
-			break;
-		case B_BG_WORKER:
-			backendDesc = "background worker";
-			break;
-		case B_BG_WRITER:
-			backendDesc = "background writer";
-			break;
-		case B_CHECKPOINTER:
-			backendDesc = "checkpointer";
-			break;
-		case B_STARTUP:
-			backendDesc = "startup";
-			break;
-		case B_WAL_RECEIVER:
-			backendDesc = "walreceiver";
-			break;
-		case B_WAL_SENDER:
-			backendDesc = "walsender";
-			break;
-		case B_WAL_WRITER:
-			backendDesc = "walwriter";
-			break;
-	}
-
-	return backendDesc;
-}
-
 /* ------------------------------------------------------------
  * Local support functions follow
  * ------------------------------------------------------------
@@ -4447,10 +4350,8 @@ PgstatCollectorMain(int argc, char *argv[])
 	pqsignal(SIGCHLD, SIG_DFL);
 	PG_SETMASK(&UnBlockSig);
 
-	/*
-	 * Identify myself via ps
-	 */
-	init_ps_display("stats collector");
+	MyBackendType = B_STATS_COLLECTOR;
+	init_ps_display(NULL);
 
 	/*
 	 * Read in existing stats files or initialize the stats to zero.

src/backend/postmaster/postmaster.c

@@ -2259,6 +2259,11 @@ retry1:
 	if (strlen(port->user_name) >= NAMEDATALEN)
 		port->user_name[NAMEDATALEN - 1] = '\0';
 
+	if (am_walsender)
+		MyBackendType = B_WAL_SENDER;
+	else
+		MyBackendType = B_BACKEND;
+
 	/*
 	 * Normal walsender backends, e.g. for streaming replication, are not
 	 * connected to a particular database. But walsenders used for logical
@@ -4422,7 +4427,7 @@ BackendInitialize(Port *port)
 	 */
 	initStringInfo(&ps_data);
 	if (am_walsender)
-		appendStringInfo(&ps_data, "%s ", pgstat_get_backend_desc(B_WAL_SENDER));
+		appendStringInfo(&ps_data, "%s ", GetBackendTypeDesc(B_WAL_SENDER));
 	appendStringInfo(&ps_data, "%s ", port->user_name);
 	if (!am_walsender)
 		appendStringInfo(&ps_data, "%s ", port->database_name);

src/backend/postmaster/syslogger.c

@@ -179,7 +179,8 @@ SysLoggerMain(int argc, char *argv[])
 
 	am_syslogger = true;
 
-	init_ps_display("logger");
+	MyBackendType = B_LOGGER;
+	init_ps_display(NULL);
 
 	/*
 	 * If we restarted, our stderr is already redirected into our own input

src/backend/utils/adt/pgstatfuncs.c

@@ -841,7 +841,7 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 			}
 			else
 				values[17] =
-					CStringGetTextDatum(pgstat_get_backend_desc(beentry->st_backendType));
+					CStringGetTextDatum(GetBackendTypeDesc(beentry->st_backendType));
 
 			/* SSL information */
 			if (beentry->st_ssl)

src/backend/utils/init/miscinit.c

@@ -57,6 +57,8 @@
 
 ProcessingMode Mode = InitProcessing;
 
+BackendType	MyBackendType;
+
 /* List of lock files to be removed at proc exit */
 static List *lock_files = NIL;
 
@@ -187,6 +189,59 @@ SwitchBackToLocalLatch(void)
 	SetLatch(MyLatch);
 }
 
+const char *
+GetBackendTypeDesc(BackendType backendType)
+{
+	const char *backendDesc = "unknown process type";
+
+	switch (backendType)
+	{
+		case B_INVALID:
+			backendDesc = "not initialized";
+			break;
+		case B_AUTOVAC_LAUNCHER:
+			backendDesc = "autovacuum launcher";
+			break;
+		case B_AUTOVAC_WORKER:
+			backendDesc = "autovacuum worker";
+			break;
+		case B_BACKEND:
+			backendDesc = "client backend";
+			break;
+		case B_BG_WORKER:
+			backendDesc = "background worker";
+			break;
+		case B_BG_WRITER:
+			backendDesc = "background writer";
+			break;
+		case B_CHECKPOINTER:
+			backendDesc = "checkpointer";
+			break;
+		case B_STARTUP:
+			backendDesc = "startup";
+			break;
+		case B_WAL_RECEIVER:
+			backendDesc = "walreceiver";
+			break;
+		case B_WAL_SENDER:
+			backendDesc = "walsender";
+			break;
+		case B_WAL_WRITER:
+			backendDesc = "walwriter";
+			break;
+		case B_ARCHIVER:
+			backendDesc = "archiver";
+			break;
+		case B_STATS_COLLECTOR:
+			backendDesc = "stats collector";
+			break;
+		case B_LOGGER:
+			backendDesc = "logger";
+			break;
+	}
+
+	return backendDesc;
+}
 
 /* ----------------------------------------------------------------
  *				database path / name support stuff

src/backend/utils/misc/ps_status.c

@@ -28,6 +28,7 @@
 
 #include "libpq/libpq.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "utils/guc.h"
 #include "utils/ps_status.h"
 
@@ -247,14 +248,20 @@ save_ps_display_args(int argc, char **argv)
 
 /*
  * Call this once during subprocess startup to set the identification
- * values.  At this point, the original argv[] array may be overwritten.
+ * values.
+ *
+ * If fixed_part is NULL, a default will be obtained from MyBackendType.
+ *
+ * At this point, the original argv[] array may be overwritten.
  */
 void
 init_ps_display(const char *fixed_part)
 {
 	bool		save_update_process_title;
 
-	Assert(fixed_part);
+	Assert(fixed_part || MyBackendType);
+	if (!fixed_part)
+		fixed_part = GetBackendTypeDesc(MyBackendType);
 
 #ifndef PS_USE_NONE
 	/* no ps display for stand-alone backend */

src/include/miscadmin.h

@@ -306,6 +306,28 @@ extern void InitStandaloneProcess(const char *argv0);
 extern void SwitchToSharedLatch(void);
 extern void SwitchBackToLocalLatch(void);
 
+typedef enum BackendType
+{
+	B_INVALID = 0,
+	B_AUTOVAC_LAUNCHER,
+	B_AUTOVAC_WORKER,
+	B_BACKEND,
+	B_BG_WORKER,
+	B_BG_WRITER,
+	B_CHECKPOINTER,
+	B_STARTUP,
+	B_WAL_RECEIVER,
+	B_WAL_SENDER,
+	B_WAL_WRITER,
+	B_ARCHIVER,
+	B_STATS_COLLECTOR,
+	B_LOGGER,
+} BackendType;
+
+extern BackendType MyBackendType;
+
+extern const char *GetBackendTypeDesc(BackendType backendType);
+
 extern void SetDatabasePath(const char *path);
 extern void checkDataDir(void);
 extern void SetDataDir(const char *dir);

src/include/pgstat.h

@@ -13,6 +13,7 @@
 
 #include "datatype/timestamp.h"
 #include "libpq/pqcomm.h"
+#include "miscadmin.h"
 #include "port/atomics.h"
 #include "portability/instr_time.h"
 #include "postmaster/pgarch.h"
@@ -712,25 +713,6 @@ typedef struct PgStat_GlobalStats
 } PgStat_GlobalStats;
 
 
-/* ----------
- * Backend types
- * ----------
- */
-typedef enum BackendType
-{
-	B_AUTOVAC_LAUNCHER,
-	B_AUTOVAC_WORKER,
-	B_BACKEND,
-	B_BG_WORKER,
-	B_BG_WRITER,
-	B_CHECKPOINTER,
-	B_STARTUP,
-	B_WAL_RECEIVER,
-	B_WAL_SENDER,
-	B_WAL_WRITER
-} BackendType;
-
-
 /* ----------
  * Backend states
  * ----------
@@ -1286,7 +1268,6 @@ extern const char *pgstat_get_wait_event_type(uint32 wait_event_info);
 extern const char *pgstat_get_backend_current_activity(int pid, bool checkUser);
 extern const char *pgstat_get_crashed_backend_activity(int pid, char *buffer,
 													   int buflen);
-extern const char *pgstat_get_backend_desc(BackendType backendType);
 
 extern void pgstat_progress_start_command(ProgressCommandType cmdtype,
 										  Oid relid);