Merge lp:~percona-toolkit-dev/percona-toolkit/fix-lock-wait-timeout-bug-946776 into lp:percona-toolkit/2.0

[Daniel Nichter]

[Daniel Nichter (daniel-nichter)]

review: Approve

=== modified file 'bin/pt-table-checksum'
--- bin/pt-table-checksum	2012-03-02 15:51:28 +0000
+++ bin/pt-table-checksum	2012-03-06 18:57:20 +0000
@@ -5940,29 +5940,37 @@
             . "level to REPEATABLE-READ.\n";
       }
 
-      # We set innodb_lock_wait_timeout=1 so that if this tool happens to cause
-      # some locking, it will be more likely to be the victim than other
-      # connections to the server, and thus disrupt the server less.
-      $sql = 'SHOW SESSION VARIABLES LIKE "innodb_lock_wait_timeout"';
-      PTDEBUG && _d($dbh, $sql);
-      my (undef, $lock_wait_timeout) = $dbh->selectrow_array($sql);
-      PTDEBUG && _d('innodb_lock_wait_timeout', $lock_wait_timeout);
-      if ( ($lock_wait_timeout || 0) > $o->get('lock-wait-timeout') ) {
-         $sql = 'SET SESSION innodb_lock_wait_timeout=1';
-         eval {
-            PTDEBUG && _d($dbh, $sql);
-            $dbh->do($sql);
-         };
-         if ( $EVAL_ERROR ) {
-            warn "Failed to $sql: $EVAL_ERROR\n"
+      # We set innodb_lock_wait_timeout=1 (the option's default value)
+      # so that if this tool happens to cause some locking, it will more
+      # likely be the victim than other connections and thus avoid disrupting
+      # the server.  The var is only dynamic with the InnoDB plugin, so
+      # if setting it fails we only warn if the server's value is greater
+      # than the desired value.  E.g. if user does --lock-wait-timeout 5
+      # and the set fails but the server's value is 1, then that's ok, but
+      # if the server's value is 10, then that's not ok.
+      my $lock_wait_timeout = $o->get('lock-wait-timeout');
+      my $set_lwt = "SET SESSION innodb_lock_wait_timeout=$lock_wait_timeout";
+      PTDEBUG && _d($dbh, $set_lwt);
+      eval {
+         $dbh->do($set_lwt);
+      };
+      if ( $EVAL_ERROR ) {
+         PTDEBUG && _d($EVAL_ERROR);
+         # Get the server's current value.
+         $sql = "SHOW SESSION VARIABLES LIKE 'innodb_lock_wait_timeout'";
+         PTDEBUG && _d($dbh, $sql);
+         my (undef, $curr_lwt) = $dbh->selectrow_array($sql);
+         PTDEBUG && _d('innodb_lock_wait_timeout on server:', $curr_lwt);
+         if ( $curr_lwt > $lock_wait_timeout ) { 
+            warn "Failed to $set_lwt: $EVAL_ERROR\n"
                . "The current innodb_lock_wait_timeout value "
-               . "$lock_wait_timeout is higher than the --lock-wait-timeout "
-               . "value " . $o->get('lock-wait-timeout') . " and the variable "
-               . "cannot be changed.  innodb_lock_wait_timeout is only dynamic "
-               . "when using the InnoDB plugin.  To prevent this warning, either "
-               . "specify --lock-wait-time=$lock_wait_timeout, or manually "
-               . "set innodb_lock_wait_timeout to a value less than or equal "
-               . "to " . $o->get('lock-wait-timeout') . " and restart MySQL.\n";
+               . "$curr_lwt is greater than the --lock-wait-timeout "
+               . "value $lock_wait_timeout and the variable cannot be "
+               . "changed.  innodb_lock_wait_timeout is only dynamic when "
+               . "using the InnoDB plugin.  To prevent this warning, either "
+               . "specify --lock-wait-time=$curr_lwt, or manually set "
+               . "innodb_lock_wait_timeout to a value less than or equal "
+               . "to $lock_wait_timeout and restart MySQL.\n";
          }
       }
    };
@@ -7989,10 +7997,13 @@
 
 type: int; default: 1
 
-Set the session value of the innodb_lock_wait_timeout variable on the master host.
-Setting this option dynamically requires the InnoDB plugin, so this works only
-on newer InnoDB and MySQL versions.  This option helps guard against long lock
-waits if the checksum queries become slow for some reason.
+Set the session value of C<innodb_lock_wait_timeout> on the master host.
+This option helps guard against long lock waits if the checksum queries
+become slow for some reason.  Setting this option dynamically requires the
+InnoDB plugin, so this works only on newer InnoDB and MySQL versions.  If
+setting the value fails and the current server value is greater than the
+specified value, then a warning is printed; else, if the current server
+value is less than or equal to the specified value, no warning is printed.
 
 =item --max-lag