Merge lp:~percona-toolkit-dev/percona-toolkit/pt-deadlock-logger-introduces-a-noise-to-mysql-1258135 into lp:percona-toolkit/2.2

[Frank Cizmich]

Background:

By default the tool prints deadlocks to stdout and, if the --dest option is provided, also inserts a log of the deadlock into a table.

To avoid duplicates in the stdout output the tool compares the last deadlocks fingerprint to the current one, discarding if they matched. (the timestamp of the deadlock is mixed in the fingerprint to avoid false negatives)

It did no such check for the output directed to the table, simply relying on the "insert ignore" directive to avoid duplicate key errors.

Fix:

Extended the fingerprint check to the table mode of logging.

Manually verified correct operation by generating deadlocks and checking binlogs.

=== modified file 'bin/pt-deadlock-logger'
--- bin/pt-deadlock-logger	2014-02-20 08:10:16 +0000
+++ bin/pt-deadlock-logger	2014-05-22 20:53:38 +0000
@@ -4601,43 +4601,44 @@
          }
       }
       else {
-         if ( $ins_sth ) {
-            eval {
-               PTDEBUG && _d('Saving deadlock to --dest');
-               foreach my $txn (
-                  sort { $a->{thread} <=> $b->{thread} } values %txns
-               ) {
-                  $ins_sth->execute(@{$txn}{@cols});
-               }
-               $dst->dbh->commit();
-            };
-            if ( my $e = $EVAL_ERROR ) {
-               PTDEBUG && _d('Error saving to --dest:', $e);
-               if ( $dst->lost_connection($e) ) {
-                  eval {
-                     $ins_sth->finish() if $ins_sth;
-                     $dst->dbh->disconnect() if $dst->dbh;
-                     $dst->connect(AutoCommit => 0);
-                     $ins_sth = $dst->dbh->prepare($ins_sql);
-                  }; 
-                  if ( $EVAL_ERROR ) {
-                     warn "Lost connection to " . $dst->name . ".  Will try "
-                        . "to reconnect in the next iteration.\n";
-                  }
-                  else {
-                     PTDEBUG && _d('Reconnected to MySQL (--dest)');
-                     redo ITERATION;
-                  }
-               }
-               else {
-                  warn "Error saving to --dest: $EVAL_ERROR";
-                  $exit_status |= 1;
-               }
-            }
-         }
-
          if ( $fingerprint ne $last_fingerprint ) {
             PTDEBUG && _d('New deadlock');
+
+            if ( $ins_sth ) {
+               eval {
+                  PTDEBUG && _d('Saving deadlock to --dest');
+                  foreach my $txn (
+                     sort { $a->{thread} <=> $b->{thread} } values %txns
+                  ) {
+                     $ins_sth->execute(@{$txn}{@cols});
+                  }
+                  $dst->dbh->commit();
+               };
+               if ( my $e = $EVAL_ERROR ) {
+                  PTDEBUG && _d('Error saving to --dest:', $e);
+                  if ( $dst->lost_connection($e) ) {
+                     eval {
+                        $ins_sth->finish() if $ins_sth;
+                        $dst->dbh->disconnect() if $dst->dbh;
+                        $dst->connect(AutoCommit => 0);
+                        $ins_sth = $dst->dbh->prepare($ins_sql);
+                     }; 
+                     if ( $EVAL_ERROR ) {
+                        warn "Lost connection to " . $dst->name . ".  Will try "
+                           . "to reconnect in the next iteration.\n";
+                     }
+                     else {
+                        PTDEBUG && _d('Reconnected to MySQL (--dest)');
+                        redo ITERATION;
+                     }
+                  }
+                  else {
+                     warn "Error saving to --dest: $EVAL_ERROR";
+                     $exit_status |= 1;
+                  }
+               }
+            }
+
             if ( !$o->get('quiet') ) {
                print join($sep, @cols), "\n";
                foreach my $txn (