Fatal error: Cannot use string offset as an array in /srv/mediawiki/php-1.26wmf6/extensions/CirrusSearch/includes/ElasticsearchIntermediary.php on line 188
This only happens under 5.3, see http://3v4l.org/iCjju
Sample code if that goes missing:
$foo = array( 'a' => array( 'b' => array( 'c' => 'baz' ) ) ); var_dump( isset( $foo['a']['b']['c']['d']['e']['f'] ) );
It looks like it completed 99.9% of the reindexing before this fataled, but to be sure i'm re-running it from mw1017 which has hhvm and doesn't experience this issue.