Reset hot standby xmin after restart
Hot_standby_feedback could be reset by reload and worked correctly, but if
the server was restarted rather than reloaded the xmin was not reset.
Force reset always if hot_standby_feedback is enabled at startup.
Ants Aasma, Craig Ringer
Reported-by: Ants Aasma
@@ -1098,7 +1098,10 @@ XLogWalRcvSendReply(bool force, bool requestReply)
* in case they don't have a watch.
*
* If the user disables feedback, send one final message to tell sender
- * to forget about the xmin on this standby.
+ * to forget about the xmin on this standby. We also send this message
+ * on first connect because a previous connection might have set xmin
+ * on a replication slot. (If we're not using a slot it's harmless to
+ * send a feedback message explicitly setting InvalidTransactionId).
*/
static void
XLogWalRcvSendHSFeedback(bool immed)
@@ -1108,7 +1111,8 @@ XLogWalRcvSendHSFeedback(bool immed)
uint32 nextEpoch;
TransactionId xmin;
static TimestampTz sendTime = 0;
- static bool master_has_standby_xmin = false;
+ /* initially true so we always send at least one feedback message */
+ static bool master_has_standby_xmin = true;
/*
* If the user doesn't want status to be reported to the master, be sure
@@ -1133,14 +1137,17 @@ XLogWalRcvSendHSFeedback(bool immed)
}
/*
- * If Hot Standby is not yet active there is nothing to send. Check this
- * after the interval has expired to reduce number of calls.
+ * If Hot Standby is not yet accepting connections there is nothing to
+ * send. Check this after the interval has expired to reduce number of
+ * calls.
+ *
+ * Bailing out here also ensures that we don't send feedback until we've
+ * read our own replication slot state, so we don't tell the master to
+ * discard needed xmin or catalog_xmin from any slots that may exist
+ * on this replica.
*/
if (!HotStandbyActive())
- {
- Assert(!master_has_standby_xmin);
return;
- }
/*
* Make the expensive call to get the oldest xmin once we are certain
