Refactor ListenSocket array.

Keep track of the used size of the array. That avoids looping through
the whole array in a few places. It doesn't matter from a performance
point of view since the array is small anyway, but this feels less
surprising and is a little less code. Now that we have an explicit
NumListenSockets variable that is statically initialized to 0, we
don't need the loop to initialize the array.

Allocate the array in PostmasterContext. The array isn't needed in
child processes, so this allows reusing that memory. We could easily
make the array resizable now, but we haven't heard any complaints
about the current 64 sockets limit.

Discussion: https://www.postgresql.org/message-id/7bb7ad65-a018-2419-742f-fa5fd877d338@iki.fi

src/backend/libpq/pqcomm.c

@@ -311,16 +311,17 @@ socket_close(int code, Datum arg)
  * specified.  For TCP ports, hostName is either NULL for all interfaces or
  * the interface to listen on, and unixSocketDir is ignored (can be NULL).
  *
- * Successfully opened sockets are added to the ListenSocket[] array (of
+ * Successfully opened sockets are appended to the ListenSockets[] array.  On
- * length MaxListen), at the first position that isn't PGINVALID_SOCKET.
+ * entry, *NumListenSockets holds the number of elements currently in the
+ * array, and it is updated to reflect the opened sockets.  MaxListen is the
+ * allocated size of the array.
  *
  * RETURNS: STATUS_OK or STATUS_ERROR
  */
-
 int
 StreamServerPort(int family, const char *hostName, unsigned short portNumber,
 				 const char *unixSocketDir,
-				 pgsocket ListenSocket[], int MaxListen)
+				 pgsocket ListenSockets[], int *NumListenSockets, int MaxListen)
 {
 	pgsocket	fd;
 	int			err;
@@ -335,7 +336,6 @@ StreamServerPort(int family, const char *hostName, unsigned short portNumber,
 	struct addrinfo *addrs = NULL,
 			   *addr;
 	struct addrinfo hint;
-	int			listen_index = 0;
 	int			added = 0;
 	char		unixSocketPath[MAXPGPATH];
 #if !defined(WIN32) || defined(IPV6_V6ONLY)
@@ -401,12 +401,7 @@ StreamServerPort(int family, const char *hostName, unsigned short portNumber,
 		}
 
 		/* See if there is still room to add 1 more socket. */
-		for (; listen_index < MaxListen; listen_index++)
+		if (*NumListenSockets == MaxListen)
-		{
-			if (ListenSocket[listen_index] == PGINVALID_SOCKET)
-				break;
-		}
-		if (listen_index >= MaxListen)
 		{
 			ereport(LOG,
 					(errmsg("could not bind to all requested addresses: MAXLISTEN (%d) exceeded",
@@ -573,7 +568,8 @@ StreamServerPort(int family, const char *hostName, unsigned short portNumber,
 					(errmsg("listening on %s address \"%s\", port %d",
 							familyDesc, addrDesc, (int) portNumber)));
 
-		ListenSocket[listen_index] = fd;
+		ListenSockets[*NumListenSockets] = fd;
+		(*NumListenSockets)++;
 		added++;
 	}
 

src/backend/postmaster/postmaster.c

@@ -227,7 +227,8 @@ int			ReservedConnections;
 
 /* The socket(s) we're listening to. */
 #define MAXLISTEN	64
-static pgsocket ListenSocket[MAXLISTEN];
+static int	NumListenSockets = 0;
+static pgsocket *ListenSockets = NULL;
 
 /* still more option variables */
 bool		EnableSSL = false;
@@ -588,7 +589,6 @@ PostmasterMain(int argc, char *argv[])
 	int			status;
 	char	   *userDoption = NULL;
 	bool		listen_addr_saved = false;
-	int			i;
 	char	   *output_config_variable = NULL;
 
 	InitProcessGlobals();
@@ -1142,17 +1142,6 @@ PostmasterMain(int argc, char *argv[])
 				 errmsg("could not remove file \"%s\": %m",
 						LOG_METAINFO_DATAFILE)));
 
-	/*
-	 * Initialize input sockets.
-	 *
-	 * Mark them all closed, and set up an on_proc_exit function that's
-	 * charged with closing the sockets again at postmaster shutdown.
-	 */
-	for (i = 0; i < MAXLISTEN; i++)
-		ListenSocket[i] = PGINVALID_SOCKET;
-
-	on_proc_exit(CloseServerPorts, 0);
-
 	/*
 	 * If enabled, start up syslogger collection subprocess
 	 */
@@ -1187,7 +1176,13 @@ PostmasterMain(int argc, char *argv[])
 
 	/*
 	 * Establish input sockets.
+	 *
+	 * First set up an on_proc_exit function that's charged with closing the
+	 * sockets again at postmaster shutdown.
 	 */
+	ListenSockets = palloc(MAXLISTEN * sizeof(pgsocket));
+	on_proc_exit(CloseServerPorts, 0);
+
 	if (ListenAddresses)
 	{
 		char	   *rawstring;
@@ -1216,12 +1211,16 @@ PostmasterMain(int argc, char *argv[])
 				status = StreamServerPort(AF_UNSPEC, NULL,
 										  (unsigned short) PostPortNumber,
 										  NULL,
-										  ListenSocket, MAXLISTEN);
+										  ListenSockets,
+										  &NumListenSockets,
+										  MAXLISTEN);
 			else
 				status = StreamServerPort(AF_UNSPEC, curhost,
 										  (unsigned short) PostPortNumber,
 										  NULL,
-										  ListenSocket, MAXLISTEN);
+										  ListenSockets,
+										  &NumListenSockets,
+										  MAXLISTEN);
 
 			if (status == STATUS_OK)
 			{
@@ -1249,7 +1248,7 @@ PostmasterMain(int argc, char *argv[])
 
 #ifdef USE_BONJOUR
 	/* Register for Bonjour only if we opened TCP socket(s) */
-	if (enable_bonjour && ListenSocket[0] != PGINVALID_SOCKET)
+	if (enable_bonjour && NumListenSockets > 0)
 	{
 		DNSServiceErrorType err;
 
@@ -1313,7 +1312,9 @@ PostmasterMain(int argc, char *argv[])
 			status = StreamServerPort(AF_UNIX, NULL,
 									  (unsigned short) PostPortNumber,
 									  socketdir,
-									  ListenSocket, MAXLISTEN);
+									  ListenSockets,
+									  &NumListenSockets,
+									  MAXLISTEN);
 
 			if (status == STATUS_OK)
 			{
@@ -1339,7 +1340,7 @@ PostmasterMain(int argc, char *argv[])
 	/*
 	 * check that we have some socket to listen on
 	 */
-	if (ListenSocket[0] == PGINVALID_SOCKET)
+	if (NumListenSockets == 0)
 		ereport(FATAL,
 				(errmsg("no socket created for listening")));
 
@@ -1487,14 +1488,9 @@ CloseServerPorts(int status, Datum arg)
 	 * before we remove the postmaster.pid lockfile; otherwise there's a race
 	 * condition if a new postmaster wants to re-use the TCP port number.
 	 */
-	for (i = 0; i < MAXLISTEN; i++)
+	for (i = 0; i < NumListenSockets; i++)
-	{
+		StreamClose(ListenSockets[i]);
-		if (ListenSocket[i] != PGINVALID_SOCKET)
+	NumListenSockets = 0;
-		{
-			StreamClose(ListenSocket[i]);
-			ListenSocket[i] = PGINVALID_SOCKET;
-		}
-	}
 
 	/*
 	 * Next, remove any filesystem entries for Unix sockets.  To avoid race
@@ -1695,29 +1691,19 @@ DetermineSleepTime(void)
 static void
 ConfigurePostmasterWaitSet(bool accept_connections)
 {
-	int			nsockets;
-
 	if (pm_wait_set)
 		FreeWaitEventSet(pm_wait_set);
 	pm_wait_set = NULL;
 
-	/* How many server sockets do we need to wait for? */
+	pm_wait_set = CreateWaitEventSet(CurrentMemoryContext,
-	nsockets = 0;
+									 accept_connections ? (1 + NumListenSockets) : 1);
-	if (accept_connections)
-	{
-		while (nsockets < MAXLISTEN &&
-			   ListenSocket[nsockets] != PGINVALID_SOCKET)
-			++nsockets;
-	}
-
-	pm_wait_set = CreateWaitEventSet(CurrentMemoryContext, 1 + nsockets);
 	AddWaitEventToSet(pm_wait_set, WL_LATCH_SET, PGINVALID_SOCKET, MyLatch,
 					  NULL);
 
 	if (accept_connections)
 	{
-		for (int i = 0; i < nsockets; i++)
+		for (int i = 0; i < NumListenSockets; i++)
-			AddWaitEventToSet(pm_wait_set, WL_SOCKET_ACCEPT, ListenSocket[i],
+			AddWaitEventToSet(pm_wait_set, WL_SOCKET_ACCEPT, ListenSockets[i],
 							  NULL, NULL);
 	}
 }
@@ -2579,14 +2565,11 @@ ClosePostmasterPorts(bool am_syslogger)
 	 * EXEC_BACKEND mode.
 	 */
 #ifndef EXEC_BACKEND
-	for (int i = 0; i < MAXLISTEN; i++)
+	for (int i = 0; i < NumListenSockets; i++)
-	{
+		StreamClose(ListenSockets[i]);
-		if (ListenSocket[i] != PGINVALID_SOCKET)
+	NumListenSockets = 0;
-		{
+	pfree(ListenSockets);
-			StreamClose(ListenSocket[i]);
+	ListenSockets = NULL;
-			ListenSocket[i] = PGINVALID_SOCKET;
-		}
-	}
 #endif
 
 	/*

src/include/libpq/libpq.h

@@ -66,7 +66,7 @@ extern PGDLLIMPORT WaitEventSet *FeBeWaitSet;
 
 extern int	StreamServerPort(int family, const char *hostName,
 							 unsigned short portNumber, const char *unixSocketDir,
-							 pgsocket ListenSocket[], int MaxListen);
+							 pgsocket ListenSocket[], int *NumListenSockets, int MaxListen);
 extern int	StreamConnection(pgsocket server_fd, Port *port);
 extern void StreamClose(pgsocket sock);
 extern void TouchSocketFiles(void);