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";