Endeavor to make pgstats buffer process (a) safe and (b) useful.

Make sure it exits immediately when collector process dies --- in old code,
buffer process would hang around and compete with the new buffer process
for packets.  Make sure it doesn't block on writing the pipe when the
collector falls more than a pipeload behind.  Avoid leaking pgstats FDs
into every backend.

src/backend/postmaster/postmaster.c

@@ -37,7 +37,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/postmaster/postmaster.c,v 1.234 2001/08/04 00:14:43 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/postmaster/postmaster.c,v 1.235 2001/08/05 02:06:50 tgl Exp $
  *
  * NOTES
  *
@@ -227,7 +227,6 @@ extern int	optreset;
 static void pmdaemonize(int argc, char *argv[]);
 static Port *ConnCreate(int serverFd);
 static void ConnFree(Port *port);
-static void ClosePostmasterPorts(void);
 static void reset_shared(unsigned short port);
 static void SIGHUP_handler(SIGNAL_ARGS);
 static void pmdie(SIGNAL_ARGS);
@@ -1241,8 +1240,8 @@ ConnFree(Port *conn)
  * that are not needed by that child process.  The postmaster still has
  * them open, of course.
  */
-static void
-ClosePostmasterPorts(void)
+void
+ClosePostmasterPorts(bool pgstat_too)
 {
 	/* Close the listen sockets */
 	if (NetServer)
@@ -1252,6 +1251,9 @@ ClosePostmasterPorts(void)
 	StreamClose(ServerSock_UNIX);
 	ServerSock_UNIX = INVALID_SOCK;
 #endif
+	/* Close pgstat control sockets, unless we're starting pgstat itself */
+	if (pgstat_too)
+		pgstat_close_sockets();
 }
 
 
@@ -1900,7 +1902,7 @@ DoBackend(Port *port)
 	 */
 
 	/* Close the postmaster's other sockets */
-	ClosePostmasterPorts();
+	ClosePostmasterPorts(true);
 
 	/* Save port etc. for ps status */
 	MyProcPort = port;
@@ -2224,7 +2226,7 @@ SSDataBase(int xlop)
 		on_exit_reset();
 
 		/* Close the postmaster's sockets */
-		ClosePostmasterPorts();
+		ClosePostmasterPorts(true);
 
 		/* Set up command-line arguments for subprocess */
 		av[ac++] = "postgres";

src/include/miscadmin.h

@@ -12,7 +12,7 @@
  * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: miscadmin.h,v 1.87 2001/06/18 21:38:02 momjian Exp $
+ * $Id: miscadmin.h,v 1.88 2001/08/05 02:06:50 tgl Exp $
  *
  * NOTES
  *	  some of the information in this file should be moved to
@@ -108,6 +108,7 @@ extern void ProcessInterrupts(void);
  * from postmaster/postmaster.c
  */
 extern int	PostmasterMain(int argc, char *argv[]);
+extern void ClosePostmasterPorts(bool pgstat_too);
 
 /*
  * from utils/init/globals.c

src/include/pgstat.h

@@ -5,7 +5,7 @@
  *
  *	Copyright (c) 2001, PostgreSQL Global Development Group
  *
- *  $Id: pgstat.h,v 1.5 2001/08/04 00:14:43 tgl Exp $
+ *  $Id: pgstat.h,v 1.6 2001/08/05 02:06:50 tgl Exp $
  * ----------
  */
 #ifndef PGSTAT_H
@@ -24,11 +24,11 @@
  * ----------
  */
 #define PGSTAT_STAT_INTERVAL	500		/* How often to write the status	*/
-										/* file in milliseconds.			*/
+										/* file, in milliseconds.			*/
 
 #define PGSTAT_DESTROY_DELAY	10000	/* How long to keep destroyed		*/
 										/* objects known to give delayed	*/
-										/* UDP packets time to arrive		*/
+										/* UDP packets time to arrive,		*/
 										/* in milliseconds.					*/
 
 #define PGSTAT_DESTROY_COUNT	(PGSTAT_DESTROY_DELAY 					\
@@ -36,7 +36,7 @@
 
 
 /* ----------
- * How much of the actual query to send to the collector.
+ * How much of the actual query string to send to the collector.
  * ----------
  */
 #define PGSTAT_ACTIVITY_SIZE	256
@@ -56,13 +56,10 @@
 #define	PGSTAT_MTYPE_RESETCOUNTER	7
 
 /* ----------
- * TODO
- * For simplicity now, the number of messages buffered in
- * pgstat_recvbuffer(). Should be an amount of bytes used
- * for a gapless wraparound buffer.
+ * Amount of space reserved in pgstat_recvbuffer().
  * ----------
  */
-#define	PGSTAT_RECVBUFFERSZ		1024
+#define	PGSTAT_RECVBUFFERSZ		((int) (1024 * sizeof(PgStat_Msg)))
 
 
 /* ----------
@@ -338,6 +335,7 @@ extern bool		pgstat_collect_blocklevel;
 extern int		pgstat_init(void);
 extern int		pgstat_start(int real_argc, char *real_argv[]);
 extern int		pgstat_ispgstat(int pid);
+extern void		pgstat_close_sockets(void);
 extern void		pgstat_beterm(int pid);
 
 /* ----------