Make a hard state change from catchup to streaming mode.

More useful state change for monitoring purposes, plus a
required change for synchronous replication patch.

diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index e04d59e1e774c69dde43e1cf8b1dccf294c8bdc2..eb99246e6d251ec4dd315ce4621d189f820d7310 100644 (file)
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -369,6 +369,16 @@ StartReplication(StartReplicationCmd * cmd)
                (errcode(ERRCODE_CANNOT_CONNECT_NOW),
        errmsg("standby connections not allowed because wal_level=minimal")));
 
+   /*
+    * When we first start replication the standby will be behind the primary.
+    * For some applications, for example, synchronous replication, it is
+    * important to have a clear state for this initial catchup mode, so we
+    * can trigger actions when we change streaming state later. We may stay
+    * in this state for a long time, which is exactly why we want to be
+    * able to monitor whether or not we are still here.
+    */
+   WalSndSetState(WALSNDSTATE_CATCHUP);
+
    /* Send a CopyBothResponse message, and start streaming */
    pq_beginmessage(&buf, 'W');
    pq_sendbyte(&buf, 0);
@@ -752,8 +762,17 @@ WalSndLoop(void)
                break;
        }
 
-       /* Update our state to indicate if we're behind or not */
-       WalSndSetState(caughtup ? WALSNDSTATE_STREAMING : WALSNDSTATE_CATCHUP);
+       /*
+        * If we're in catchup state, see if its time to move to streaming.
+        * This is an important state change for users, since before this
+        * point data loss might occur if the primary dies and we need to
+        * failover to the standby. The state change is also important for
+        * synchronous replication, since commits that started to wait at
+        * that point might wait for some time.
+        */
+       if (MyWalSnd->state == WALSNDSTATE_CATCHUP && caughtup)
+           WalSndSetState(WALSNDSTATE_STREAMING);
+
        ProcessRepliesIfAny();
    }