Doctrine 2 memory hogging - doctrine-orm

Question

I'm using Doctrine 2 with my ZF2 project, but i'm getting some weird problem with my server CPU and memory. And my server simply crashes.
I'm getting a lot of sleep state querys and they seem not to get cleaned.
mysql> show processlist;
+---------+--------------+-----------+------------------+----------------+------+--------------------+------------------------------------------------------------------------------------------------------+
| Id | User | Host | db | Command | Time | State | Info |
+---------+--------------+-----------+------------------+----------------+------+--------------------+------------------------------------------------------------------------------------------------------+
| 2832346 | leechprotect | localhost | leechprotect | Sleep | 197 | | NULL |
| 2832629 | db_user | localhost | db_exemple | Sleep | 3 | | NULL |
| 2832643 | db_user | localhost | db_exemple | Sleep | 3 | | NULL |
| 2832646 | db_user | localhost | db_exemple | Sleep | 3 | | NULL |
| 2832664 | db_user | localhost | db_exemple | Sleep | 154 | | NULL |
| 2832666 | db_user | localhost | db_exemple | Sleep | 153 | | NULL |
| 2832669 | db_user | localhost | db_exemple | Sleep | 152 | | NULL |
| 2832674 | db_user | localhost | db_exemple | Sleep | 7 | | NULL |
| 2832681 | db_user | localhost | db_exemple | Sleep | 1 | | NULL |
| 2832683 | db_user | localhost | db_exemple | Sleep | 4 | | NULL |
| 2832690 | db_user | localhost | db_exemple | Sleep | 149 | | NULL |
(.......)
Also, it seems php GC is not cleaning all the objects from memory, or even kill processes.
Is there a way to disable the cache system? Would it improve the use of my resorces=
Most my querys are similar to:
$query = $this->createQueryBuilder('i');
$query->innerJoin('\Application\Relation', 'r', 'WITH', 'r.child = i.id');
$query->innerJoin('\Application\Taxonomy', 't', 'WITH', 't.id = r.taxonomy');
$query->where('t.type = :type')->setParameter('type', $relation);
$query->groupBy('i.id');
$items = $query->getQuery()->getResult(2);
Thanks in advance.

Answer 1

Firstly check the mysql's wait_timout variable. From the documentation:
Wait_timeout : The number of seconds the server waits for activity on
a noninteractive connection before closing it.
In normal flow (which not using persistent connections), php closes the connection automatically after script execution. To ensure there are no sleeping threads; at the end of your script simply close the connection:
$entityManager->getConnection()->close();
If these queries are running in a big while/for loop, you might want to read doctrine 2 batch processing documentation.