Merge lp:~percona-toolkit-dev/percona-toolkit/pt-heartbeat-check-read-only-option-does-not-prevent-creates-or-inserts-1328686 into lp:~percona-toolkit-dev/percona-toolkit/release-2.2.12

[Frank Cizmich]

Problem:

Some users need to start pt-heartbeat on a server with read_only enabled, and enable writing at a later time.
The tool only checks for this after initializing tables and doing the first row insert, thus it fails if it begins to run on a read_only server.

Fix:
Before initializing, if --check-read-only and --update options are given, the tool waits for read_only to be disabled , checking at regular intervals.
--run-time is also honored, so if it is still waiting when run-time is reached, it exits.

[Daniel Nichter (daniel-nichter)]

review: Needs Fixing

[lp:~percona-toolkit-dev/percona-toolkit/pt-heartbeat-check-read-only-option-does-not-prevent-creates-or-inserts-1328686]

630. By Frank Cizmich on 2014-11-06

Added check for sentinel file.

[Frank Cizmich (frank-cizmich)]

This duplicates some code, but trying to avoid that seems to complicate things too much.

=== modified file 'bin/pt-heartbeat'
--- bin/pt-heartbeat	2014-09-25 13:48:22 +0000
+++ bin/pt-heartbeat	2014-11-06 17:05:49 +0000
@@ -4892,6 +4892,32 @@
    $dbh->do("USE `$db`");
 
    # ########################################################################
+   # If --check-read-only option was given and we are in --update mode 
+   # we wait until server is writable , or run-time is over, or sentinel file
+   # We also do this check after daemon is up and running, but it is necessary 
+   # to check this before attempting to create the table and inserting rows
+   # https://bugs.launchpad.net/percona-toolkit/+bug/1328686
+   # #######################################################################
+   if ( $o->get('check-read-only') && $o->get('update') ) {
+      PTDEBUG && _d('Checking if server is read_only');
+      if ( server_is_readonly($dbh) &&  PTDEBUG ) {
+         _d('Server is read-only, waiting')
+      }
+      my $start_time = time;
+      my $run_time   = $o->get('run-time');
+      my $interval   = $o->get('interval') || 5;
+      while (server_is_readonly($dbh)) {
+         sleep($interval); 
+         if ( 
+            ($run_time && $run_time < time - $start_time)
+            || -f $sentinel
+         ) {
+            return 0;
+         }
+      }
+   }
+
+   # ########################################################################
    # Create the heartbeat table if --create-table was given.
    # ########################################################################
    my $utc       = $o->get('utc');