symfony2 free -m out of memory - memory

Question

I have symfony2 app out there. But we have RAM memory problems... It works like a charm when there is 50 active people (google analytics).
I select data from DB usally like this:
$qb=$this->createQueryBuilder('s')
->addSelect('u')
->where('s.user = :user')
->andWhere('s.admin_status = false')
->andWhere('s.typ_statusu != :group')
->setParameter('user', $user)
->setParameter('group', 'group')
->innerJoin('s.user', 'u')
->orderBy('s.time', 'DESC')
->setMaxResults(15);
return $query=$qb->getQuery()->getResult();
The queries are fast i dont have problem with them.
Let me please know exactly what you need and i will paste it here. I need to fix it so much..
BUT THE PROBLEM COME NOW: When there is 470people at the same time.. (google analytics) there is about 7GB of memory away... then it fall down after peak to 5GB. But WHY SO MUCH??? My scripts take from 10-17MB of memory usage in app_dev.
I also use APC. How can i solve this situation? Why is there so much memory consumed? Thx for any advice!!
Whats your average memory?
BTW: When i will not solve this i will be in big troubles.

Answer 1

One problem could be doctrine and if you are hydrating too much obejcts in every single request.

Answer 2

Set max execution time of a script to only 30 seconds:
max_execution_time = 30
Set APC shm_size to something reasonable compared to your memory:
apc.shm_size = 256M
Then optimize your query. And if you use php/symfony in cli, you better limit the resource usage for php in cli too.

Answer 3

Ensure you are understanding correctly memory consumption. http://blog.scoutapp.com/articles/2010/10/06/determining-free-memory-on-linux
To fast Apc you can remove the modified check with apc.stat = 0 but you will need to clear apc-cache every time you modify existing files: http://www.php.net/manual/en/apc.configuration.php#ini.apc.stat
To reduce memory consumption reduce hydration my adding ->select('x') and fetching only the essential.
To optimize memory consumption enable mysql-cache, something like /etc/mysql/my.cnf:
query_cache_size=128M
query_cache_limit=1M
Do not forget to enable and check your slow-query-log to avoid bottlenecks.

Answer 4

I suspect that your page has more that one query. How many queries happening on the page? Worst thing in the doctrine is the ability to make queries through getter(ex. getComments()). If you are using a many-to-many relation, this leads to huge problems. You can see all queries via profiler in dev environment.
Also possible, that problem in the settings of apache or php. Incorrect settings of php-fpm lead to problems too. The best solution is to stress test your server with tools like siege and look what goes on through the htop or top. 300 peoples can be a heavy load for the "naked" apache

Answer 5

Have you ever tried to retrieve scalar results instead of a collection of objects ?
// [...]
return $query=$qb->getQuery()->getScalarResult();
http://docs.doctrine-project.org/en/latest/reference/query-builder.html#executing-a-query
http://doctrine-orm.readthedocs.org/en/2.0.x/reference/dql-doctrine-query-language.html#query-result-formats
At symfony configuration level, have you double-checked your configuration to ensure caching has been enabled properly ?
http://symfony.com/doc/current/reference/configuration/doctrine.html#caching-drivers
Detaching entities from your entity manager could prove useful depending on your overall process:
http://docs.doctrine-project.org/en/2.0.x/reference/working-with-objects.html#detaching-entities