PHP-FPM processes holding onto MongoDB connection states - centos

Question

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.
Edit:
While I wait for the driver to be fixed in this regard, my current workaround is to do a quick polling to determine if the driver can handle requests and then load or not load the MongoDB library/run queries if it can't connect/query:
try
{
// connect
$mongo = new Mongo("mongodb://localhost:27017");
// try to do anything with connection handle
try
{
$mongo->YOUR_DB->YOUR_COLLECTION->findOne();
$mongo->close();
define('MONGO_STATE', TRUE);
}
catch(MongoCursorException $e)
{
$mongo->close();
error_log('Error connecting to MongoDB: ' . $e->getMessage() );
define('MONGO_STATE', FALSE);
}
}
catch(MongoConnectionException $e)
{
error_log('Error connecting to MongoDB: ' . $e->getMessage() );
define('MONGO_STATE', FALSE);
}

Answer 1

The PHP mongo driver connectivity code is getting a big overhaul in the 1.3 release, currently in beta2 as of writing this. Based on your description, your issues may be resolved by the fixes for:
https://jira.mongodb.org/browse/PHP-158
https://jira.mongodb.org/browse/PHP-465
Once it is released you will be able to see the full list of fixes here:
https://jira.mongodb.org/browse/PHP/fixforversion/10499
Or, alternatively on the PECL site. If you can test 1.3 and confirm that your issues are still present then I'm sure the driver devs would love to hear from you before the 1.3.0 release, especially if it is easily reproducible.