Details
-
Bug
-
Status: Done
-
High
-
Resolution: Fixed
-
3.0.10, 3.0.11, 3.0.12, 3.0.13
-
None
-
1
Description
As of percona toolkit 3.0.10, the release notes state that pt-table-checksum disables the QRT plugin. Presumably this was to be a configurable option, based on the --disable-qrt-plugin command-line flag.
However, pt-table-checksum forcibly disables QRT on all slaves, regardless of the value of this option - and unless this option was explicitly set to TRUE, it remains OFF.
Disabling QRT on the master is controlled by an if() statement - if ($o->get('disable-qrt-plugin') on line 10158 (this is PT 3.0.13)
But there is no such if() statement for the slaves, beginning on line 10492.
for my $slave (@$slaves) {
my $qrt_plugin_status;
eval {
($qrt_plugin_status) = $slave->{dbh}->selectrow_arrayref('SELECT @@QUERY_RESPONSE_TIME_SESSION_STATS' );
};
if ($EVAL_ERROR) {
PTDEBUG && _d('QRT plugin is not installed on slave '.$slave->{dsn_name});
$slave->{qrt_plugin_status} = undef;
next;
}
$slave->{qrt_plugin_status} = $qrt_plugin_status->[0];
if ($slave->{qrt_plugin_status}) {
PTDEBUG && _d("Disabling qrt plugin state on slave ".$slave->{dsn_name});
$slave->{dbh}->do('SET GLOBAL query_response_time_stats = off');
}
}
Then on line 11523, when the QRT plugin is reset back to its original value, once again the code is wrapped in a conditional:
# Restore origin QRT pligin state if ($o->get('disable-qrt-plugin')) { eval { if ($original_qrt_plugin_master_status) { PTDEBUG && _d("Restoring qrt plugin state on master server"); $master_dbh->do("SET GLOBAL query_response_time_stats = $original_qrt_plugin_master_status->[0]"); } for my $slave (@$slaves) { if ($slave->{qrt_plugin_status}) { PTDEBUG && _d("Restoring qrt plugin state on slave ".$slave->{dsn_name}); $slave->{dbh}->do("SET GLOBAL query_response_time_stats = $slave->{qrt_plugin_status}"); } } }; if ($EVAL_ERROR) { warn "Cannot restore qrt_plugin status: $EVAL_ERROR"; } }
So, QRT silently gets shut off and it never comes back on - and should your slave get promoted to master, you'll be wondering why you suddenly have no metrics.
The fix for this is trivial - wrap that loop over the slaves in an "if $o->get('disable-qrt-plugin') { .. }"
Attachments
Issue Links
- mentioned in
-
Page Loading...