Final rearrangement of main postgresql child process (ie.

BackendFork/SSDataBase/pgstat) startup, to allow fork/exec calls to
closely mimic (the soon to be provided) Win32 CreateProcess equivalent
calls.

Claudio Natoli

src/backend/bootstrap/bootstrap.c

@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/bootstrap/bootstrap.c,v 1.172 2003/12/25 03:52:50 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/bootstrap/bootstrap.c,v 1.173 2004/01/06 23:15:22 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -51,7 +51,7 @@
 #ifdef EXEC_BACKEND
 typedef struct Port Port;
 extern void SSDataBaseInit(int);
-extern void read_backend_variables(pid_t, Port*);
+extern void read_backend_variables(unsigned long, Port*);
 #endif
 
 extern int	Int_yyparse(void);
@@ -231,6 +231,9 @@ BootstrapMain(int argc, char *argv[])
 	int			flag;
 	int			xlogop = BS_XLOG_NOP;
 	char	   *potential_DataDir = NULL;
+#ifdef EXEC_BACKEND
+	unsigned long	backendID = 0;
+#endif
 
 	/*
 	 * initialize globals
@@ -291,10 +294,15 @@ BootstrapMain(int argc, char *argv[])
 				break;
 			case 'p':
 #ifdef EXEC_BACKEND
-				IsUnderPostmaster = true;
+				{
+					char buf[MAXPGPATH];
+					IsUnderPostmaster = true;
+					sscanf(optarg,"%lu,%s",&backendID,buf);
+					dbname = strdup(buf);
+				}
 #endif
 				dbname = strdup(optarg);
-					break;
+				break;
 			case 'B':
 				SetConfigOption("shared_buffers", optarg, PGC_POSTMASTER, PGC_S_ARGV);
 				break;
@@ -363,7 +371,7 @@ BootstrapMain(int argc, char *argv[])
 	{
 #ifdef EXEC_BACKEND
 		read_nondefault_variables();
-		read_backend_variables(getpid(),NULL);
+		read_backend_variables(backendID,NULL);
 
 		SSDataBaseInit(xlogop);
 #endif
@@ -431,11 +439,11 @@ BootstrapMain(int argc, char *argv[])
 		switch (xlogop)
 		{
 			case BS_XLOG_BGWRITER:
-				InitDummyProcess(DUMMY_PROC_BGWRITER);	
+				InitDummyProcess(DUMMY_PROC_BGWRITER);
 				break;
-		
+
 			default:
-				InitDummyProcess(DUMMY_PROC_DEFAULT);	
+				InitDummyProcess(DUMMY_PROC_DEFAULT);
 				break;
 		}
 	}

src/backend/main/main.c

@@ -13,7 +13,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/main/main.c,v 1.69 2003/12/25 03:52:50 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/main/main.c,v 1.70 2004/01/06 23:15:22 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -203,9 +203,9 @@ main(int argc, char *argv[])
 
 	/*
 	 * Now dispatch to one of PostmasterMain, PostgresMain, GucInfoMain,
-	 * pgstat_main, pgstat_mainChild or BootstrapMain depending on the
-	 * program name (and possibly first argument) we were called with.
-	 * The lack of consistency here is historical.
+	 * SubPostmasterMain, pgstat_main, pgstat_mainChild or BootstrapMain
+	 * depending on the program name (and possibly first argument) we
+	 * were called with. The lack of consistency here is historical.
 	 */
 	len = strlen(new_argv[0]);
 
@@ -223,6 +223,16 @@ main(int argc, char *argv[])
 		exit(BootstrapMain(argc - 1, new_argv + 1));
 
 #ifdef EXEC_BACKEND
+	/*
+	 * If the first argument is "-forkexec", then invoke SubPostmasterMain. Note
+	 * we remove "-forkexec" from the arguments passed on to SubPostmasterMain.
+	 */
+	if (argc > 1 && strcmp(new_argv[1], "-forkexec") == 0)
+	{
+		SubPostmasterMain(argc - 2, new_argv + 2);
+		exit(0);
+	}
+
 	/*
 	 * If the first argument is "-statBuf", then invoke pgstat_main. Note
 	 * we remove "-statBuf" from the arguments passed on to pgstat_main.

src/backend/postmaster/pgstat.c

@@ -13,7 +13,7 @@
  *
  *	Copyright (c) 2001-2003, PostgreSQL Global Development Group
  *
- *	$PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.50 2003/12/25 03:52:51 momjian Exp $
+ *	$PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.51 2004/01/06 23:15:22 momjian Exp $
  * ----------
  */
 #include "postgres.h"
@@ -107,7 +107,7 @@ static char pgStat_fname[MAXPGPATH];
  * ----------
  */
 #ifdef EXEC_BACKEND
-static void pgstat_exec(STATS_PROCESS_TYPE procType);
+static pid_t pgstat_forkexec(STATS_PROCESS_TYPE procType);
 static void pgstat_parseArgs(PGSTAT_FORK_ARGS);
 #endif
 NON_EXEC_STATIC void pgstat_main(PGSTAT_FORK_ARGS);
@@ -337,15 +337,16 @@ startup_failed:
 #ifdef EXEC_BACKEND
 
 /* ----------
- * pgstat_exec() -
+ * pgstat_forkexec() -
  *
- * Used to format up the arglist for, and exec, statistics
+ * Used to format up the arglist for, then fork and exec, statistics
  * (buffer and collector) processes
  *
  */
-static void
-pgstat_exec(STATS_PROCESS_TYPE procType)
+static pid_t
+pgstat_forkexec(STATS_PROCESS_TYPE procType)
 {
+	pid_t pid;
 	char *av[11];
 	int ac = 0, bufc = 0, i;
 	char pgstatBuf[8][MAXPGPATH];
@@ -387,9 +388,12 @@ pgstat_exec(STATS_PROCESS_TYPE procType)
 	av[ac++] = NULL;
 	Assert(ac <= lengthof(av));
 
-	if (execv(pg_pathname,av) == -1)
+	/* Fire off execv in child */
+	if ((pid = fork()) == 0 && (execv(pg_pathname,av) == -1))
 		/* FIXME: [fork/exec] suggestions for what to do here? Can't call elog... */
-		Assert(false);
+		abort();
+
+	return pid; /* Parent returns pid */
 }
 
 
@@ -479,7 +483,11 @@ pgstat_start(void)
 	beos_before_backend_startup();
 #endif
 
+#ifdef EXEC_BACKEND
+	switch ((pgStatSock = (int) pgstat_forkexec(STAT_PROC_BUFFER)))
+#else
 	switch ((pgStatPid = (int) fork()))
+#endif
 	{
 		case -1:
 #ifdef __BEOS__
@@ -490,32 +498,27 @@ pgstat_start(void)
 					(errmsg("could not fork statistics buffer: %m")));
 			return;
 
+#ifndef EXEC_BACKEND
 		case 0:
+			/* in postmaster child ... */
+#ifdef __BEOS__
+			/* Specific beos actions after backend startup */
+			beos_backend_startup();
+#endif
+			/* Close the postmaster's sockets, except for pgstat link */
+			ClosePostmasterPorts(false);
+
+			/* Drop our connection to postmaster's shared memory, as well */
+			PGSharedMemoryDetach();
+
+			pgstat_main();
 			break;
+#endif
 
 		default:
 			pgstat_is_running = true;
 			return;
 	}
-
-	/* in postmaster child ... */
-
-#ifdef __BEOS__
-	/* Specific beos actions after backend startup */
-	beos_backend_startup();
-#endif
-
-	/* Close the postmaster's sockets, except for pgstat link */
-	ClosePostmasterPorts(false);
-
-	/* Drop our connection to postmaster's shared memory, as well */
-	PGSharedMemoryDetach();
-
-#ifdef EXEC_BACKEND
-	pgstat_exec(STAT_PROC_BUFFER);
-#else
-	pgstat_main();
-#endif
 }
 
 
@@ -1385,28 +1388,31 @@ pgstat_main(PGSTAT_FORK_ARGS)
 		exit(1);
 	}
 
+#ifdef EXEC_BACKEND
+	/* child becomes collector process */
+	switch (pgstat_forkexec(STAT_PROC_COLLECTOR))
+#else
 	switch (fork())
+#endif
 	{
 		case -1:
 			ereport(LOG,
 					(errmsg("could not fork statistics collector: %m")));
 			exit(1);
 
+#ifndef EXEC_BACKEND
 		case 0:
 			/* child becomes collector process */
-#ifdef EXEC_BACKEND
-			pgstat_exec(STAT_PROC_COLLECTOR);
-#else
 			pgstat_mainChild();
+			break;
 #endif
-			exit(0);
 
 		default:
 			/* parent becomes buffer process */
 			closesocket(pgStatPipe[0]);
 			pgstat_recvbuffer();
-			exit(0);
 	}
+	exit(0);
 }
 
 

src/backend/tcop/postgres.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/tcop/postgres.c,v 1.382 2004/01/06 17:36:31 neilc Exp $
+ *	  $PostgreSQL: pgsql/src/backend/tcop/postgres.c,v 1.383 2004/01/06 23:15:22 momjian Exp $
  *
  * NOTES
  *	  this is the "main" module of the postgres backend and
@@ -68,11 +68,6 @@
 extern int	optind;
 extern char *optarg;
 
-#ifdef EXEC_BACKEND
-extern bool BackendInit(Port*);
-extern void read_backend_variables(pid_t, Port*);
-#endif
-
 /* ----------------
  *		global variables
  * ----------------
@@ -2063,7 +2058,7 @@ PostgresMain(int argc, char *argv[], const char *username)
 	 *
 	 * If we are running under the postmaster, this is done already.
 	 */
-	if (!IsUnderPostmaster || ExecBackend)
+	if (!IsUnderPostmaster)
 		MemoryContextInit();
 
 	set_ps_display("startup");
@@ -2268,11 +2263,7 @@ PostgresMain(int argc, char *argv[], const char *username)
 				 */
 				if (secure)
 				{
-#ifdef EXEC_BACKEND
-					IsUnderPostmaster = true;
-#else
 					dbname = strdup(optarg);
-#endif
 
 					secure = false;		/* subsequent switches are NOT
 										 * secure */
@@ -2478,25 +2469,7 @@ PostgresMain(int argc, char *argv[], const char *username)
 	if (IsUnderPostmaster)
 	{
 #ifdef EXEC_BACKEND
-		Port *port =(Port*)malloc(sizeof(Port));
-		if (port == NULL)
-			ereport(ERROR,
-				(errcode(ERRCODE_OUT_OF_MEMORY),
-				errmsg("insufficient memory to allocate port")));
-
 		read_nondefault_variables();
-		read_backend_variables(getpid(),port);
-
-		/* FIXME: [fork/exec] Ugh */
-		load_hba();
-		load_ident();
-		load_user();
-		load_group();
-
-		if (!BackendInit(port))
-			return -1;
-
-		dbname = port->database_name;
 #endif
 	} else
 		ProcessConfigFile(PGC_POSTMASTER);

src/include/miscadmin.h

@@ -12,7 +12,7 @@
  * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/miscadmin.h,v 1.141 2004/01/06 17:36:31 neilc Exp $
+ * $PostgreSQL: pgsql/src/include/miscadmin.h,v 1.142 2004/01/06 23:15:22 momjian Exp $
  *
  * NOTES
  *	  some of the information in this file should be moved to
@@ -115,6 +115,9 @@ extern bool ClientAuthInProgress;
 extern const bool ExecBackend;
 
 extern int	PostmasterMain(int argc, char *argv[]);
+#ifdef EXEC_BACKEND
+extern void SubPostmasterMain(int argc, char* argv[]);
+#endif
 extern void ClosePostmasterPorts(bool pgstat_too);
 
 /*