Move canAcceptConnections check from ProcessStartupPacket to caller.

The check is not about processing the startup packet, so the calling
function seems like a more natural place. I'm also working on a patch
that moves 'canAcceptConnections' out of the Port struct, and this
makes that refactoring more convenient.

Reviewed-by: Tristan Partin
Discussion: https://www.postgresql.org/message-id/7a59b073-5b5b-151e-7ed3-8b01ff7ce9ef@iki.fi

Author: hlinnaka

src/backend/postmaster/postmaster.c

@@ -2281,49 +2281,6 @@ ProcessStartupPacket(Port *port, bool ssl_done, bool gss_done)
 	 */
 	MemoryContextSwitchTo(oldcontext);
 
-	/*
-	 * If we're going to reject the connection due to database state, say so
-	 * now instead of wasting cycles on an authentication exchange. (This also
-	 * allows a pg_ping utility to be written.)
-	 */
-	switch (port->canAcceptConnections)
-	{
-		case CAC_STARTUP:
-			ereport(FATAL,
-					(errcode(ERRCODE_CANNOT_CONNECT_NOW),
-					 errmsg("the database system is starting up")));
-			break;
-		case CAC_NOTCONSISTENT:
-			if (EnableHotStandby)
-				ereport(FATAL,
-						(errcode(ERRCODE_CANNOT_CONNECT_NOW),
-						 errmsg("the database system is not yet accepting connections"),
-						 errdetail("Consistent recovery state has not been yet reached.")));
-			else
-				ereport(FATAL,
-						(errcode(ERRCODE_CANNOT_CONNECT_NOW),
-						 errmsg("the database system is not accepting connections"),
-						 errdetail("Hot standby mode is disabled.")));
-			break;
-		case CAC_SHUTDOWN:
-			ereport(FATAL,
-					(errcode(ERRCODE_CANNOT_CONNECT_NOW),
-					 errmsg("the database system is shutting down")));
-			break;
-		case CAC_RECOVERY:
-			ereport(FATAL,
-					(errcode(ERRCODE_CANNOT_CONNECT_NOW),
-					 errmsg("the database system is in recovery mode")));
-			break;
-		case CAC_TOOMANY:
-			ereport(FATAL,
-					(errcode(ERRCODE_TOO_MANY_CONNECTIONS),
-					 errmsg("sorry, too many clients already")));
-			break;
-		case CAC_OK:
-			break;
-	}
-
 	return STATUS_OK;
 }
 
@@ -4360,6 +4317,49 @@ BackendInitialize(Port *port)
 	 */
 	status = ProcessStartupPacket(port, false, false);
 
+	/*
+	 * If we're going to reject the connection due to database state, say so
+	 * now instead of wasting cycles on an authentication exchange. (This also
+	 * allows a pg_ping utility to be written.)
+	 */
+	switch (port->canAcceptConnections)
+	{
+		case CAC_STARTUP:
+			ereport(FATAL,
+					(errcode(ERRCODE_CANNOT_CONNECT_NOW),
+					 errmsg("the database system is starting up")));
+			break;
+		case CAC_NOTCONSISTENT:
+			if (EnableHotStandby)
+				ereport(FATAL,
+						(errcode(ERRCODE_CANNOT_CONNECT_NOW),
+						 errmsg("the database system is not yet accepting connections"),
+						 errdetail("Consistent recovery state has not been yet reached.")));
+			else
+				ereport(FATAL,
+						(errcode(ERRCODE_CANNOT_CONNECT_NOW),
+						 errmsg("the database system is not accepting connections"),
+						 errdetail("Hot standby mode is disabled.")));
+			break;
+		case CAC_SHUTDOWN:
+			ereport(FATAL,
+					(errcode(ERRCODE_CANNOT_CONNECT_NOW),
+					 errmsg("the database system is shutting down")));
+			break;
+		case CAC_RECOVERY:
+			ereport(FATAL,
+					(errcode(ERRCODE_CANNOT_CONNECT_NOW),
+					 errmsg("the database system is in recovery mode")));
+			break;
+		case CAC_TOOMANY:
+			ereport(FATAL,
+					(errcode(ERRCODE_TOO_MANY_CONNECTIONS),
+					 errmsg("sorry, too many clients already")));
+			break;
+		case CAC_OK:
+			break;
+	}
+
 	/*
 	 * Disable the timeout, and prevent SIGTERM again.
 	 */