For the relevant part of our server stack, we're running:

• NGINX 1.2.3
• PHP-FPM 5.3.10 with PECL mongo 1.2.12
• MongoDB 2.0.7
• CentOS 6.2

We're getting some strange, but predictable behavior when the MongoDB server goes away (crashes, gets killed, etc). Even with a try/catch block around the connection code, i.e:

try
{
    $mdb = new Mongo('mongodb://localhost:27017');
}
catch (MongoConnectionException $e)
{
    die( $e->getMessage() );
}

$db = $mdb->selectDB('collection_name');

Depending on which PHP-FPM workers have connected to mongo already, the connection state is cached, causing further exceptions to go unhandled, because the $mdb connection handler can't be used. The troubling thing is that the try does not consistently fail for a considerable amount of time, up to 15 minutes later, when -- I assume -- the php-fpm processes die/respawn.

Essentially, the behavior is that when you hit a worker that hasn't connected to mongo yet, you get the die message above, and when you connect to a worker that has, you get an unhandled exception from $mdb->selectDB('collection_name'); because catch does not run.

When PHP is a single process, i.e. via Apache with mod_php, this behavior does not occur. Just for posterity, going back to Apache/mod_php is not an option for us at this time.

Is there a way to fix this behavior? I don't want the connection state to be inconsistent between different php-fpm processes.