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Prevent invalid replication_lag values being written to the monitoring table

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A fix for this was introduced with commit ee9270fe8d
and removed in 4f1c67a1bf.

Refactor the original fix to simply omit attempting to write an invalid entry
to the monitoring table.
This commit is contained in:
Ian Barwick
2016-01-04 13:31:50 +09:00
parent 490e12b1af
commit 7a4d84379c
1 changed files with 22 additions and 3 deletions
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25
repmgrd.c
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@@ -657,6 +657,7 @@ standby_monitor(void)
char last_wal_standby_received[MAXLEN];
char last_wal_standby_applied[MAXLEN];
char last_wal_standby_applied_timestamp[MAXLEN];
bool last_wal_standby_received_gte_replayed;
char sqlquery[QUERY_STR_LEN];
XLogRecPtr lsn_master;
@@ -822,7 +823,7 @@ standby_monitor(void)
PQfinish(upstream_conn);
continue_monitoring_standby:
continue_monitoring_standby:
/* Check if we still are a standby, we could have been promoted */
do
{
@@ -881,7 +882,6 @@ standby_monitor(void)
if (!monitoring_history)
return;
/*
* If original master has gone away we'll need to get the new one
* from the upstream node to write monitoring information
@@ -943,7 +943,8 @@ standby_monitor(void)
/* Get local xlog info */
sqlquery_snprintf(sqlquery,
"SELECT CURRENT_TIMESTAMP, pg_last_xlog_receive_location(), "
"pg_last_xlog_replay_location(), pg_last_xact_replay_timestamp()");
"pg_last_xlog_replay_location(), pg_last_xact_replay_timestamp(), "
"pg_last_xlog_receive_location() >= pg_last_xlog_replay_location()");
res = PQexec(my_local_conn, sqlquery);
if (PQresultStatus(res) != PGRES_TUPLES_OK)
@@ -958,9 +959,27 @@ standby_monitor(void)
strncpy(last_wal_standby_received, PQgetvalue(res, 0, 1), MAXLEN);
strncpy(last_wal_standby_applied, PQgetvalue(res, 0, 2), MAXLEN);
strncpy(last_wal_standby_applied_timestamp, PQgetvalue(res, 0, 3), MAXLEN);
last_wal_standby_received_gte_replayed = (strcmp(PQgetvalue(res, 0, 4), "t") == 0)
? true
: false;
PQclear(res);
/*
* In the unusual event of a standby becoming disconnected from the primary,
* while this repmgrd remains connected to the primary, subtracting
* "lsn_standby_applied" from "lsn_standby_received" and coercing to
* (long long unsigned int) will result in a meaningless, very large
* value which will overflow a BIGINT column and spew error messages into the
* PostgreSQL log. In the absence of a better strategy, skip attempting
* to insert a monitoring record.
*/
if (last_wal_standby_received_gte_replayed == false)
{
log_verbose(LOG_WARNING,
"Invalid replication_lag value calculated - is this standby connected to its upstream?\n");
return;
}
/* Get master xlog info */
sqlquery_snprintf(sqlquery, "SELECT pg_catalog.pg_current_xlog_location()");