Create submodule to store PHP sessions in Redis

Forced rebase against dev branch. Here's a patch if anyone needs it.

Added a commit to make the submodule compatible with Drupal 10

Merge request is failing.

Ah ok, it wasn't that simple then, I'll do a more thorough job, thanks for pointing it out :)

You can easily override the Drupal session factory via *services.yml to the Redis session factory (a component that Symfony provides).

services:
  redis.client:
    class: Redis # Your Redis client class.
    factory: [ '@redis.factory', 'getClient' ]
  session_handler.storage:
    class: Symfony\Component\HttpFoundation\Session\Storage\Handler\RedisSessionHandler
    arguments: [ '@redis.client', { prefix: 'drupal_session:' } ]

I'm not sure if there are any downsides to this approach. If not, then mentioning this feature in the README would be helpful.

@kksandr

How your redis.client class looks like?

@hmdnawaz I use phpredis, so it's class: Redis, which is the global class provided by that PHP extension.

In case of Drupal redis module, can we use?

services:
  redis.client:
    class: Drupal\redis\Client\PhpRedis # Your Redis client class.
    factory: [ '@redis.factory', 'getClient' ]
  session_handler.storage:
    class: Symfony\Component\HttpFoundation\Session\Storage\Handler\RedisSessionHandler
    arguments: [ '@redis.client', { prefix: 'drupal_session:' } ]

#52: works for me ;) thanks!

There is an issue when using the RedisSessionHandler. When you clear the cache from the UI or use Drush, the logged-in user gets logged out.

#52: works for me ;)
just adding steps

in your custom module add

services:
  redis.client:
    class: Drupal\redis\Client\PhpRedis
    factory: [ '@redis.factory', 'getClient' ]

  session_handler.storage:
    class: Symfony\Component\HttpFoundation\Session\Storage\Handler\RedisSessionHandler
    arguments: [ '@redis.client', { prefix: 'drupal_session:' } ]

and in settings.php add :
$settings['session_handler_class'] = 'Symfony\Component\HttpFoundation\Session\Storage\Handler\RedisSessionHandler';

hope this help to others :)

I propose we adjust this issue to fully document that approach in the module code and docs.

I'm not sure what exactly is the "correct" way to do this... on a recent project we simply did $settings['session_storage']['class'] = 'Drupal\redis\Cache\PhpRedis'; and it seemed to work pretty well! if anyone can provide a comparison or justification on the best approach, I would much appreciate it.

In general, for our project, which consists of mostly logged in users, we saw a ~600% increase in throughput under load between that setting and also adding $settings['session_write_lock'] = FALSE;. Managing sessions through Redis appears to be a boon for performance and it would be great if this got rolled into the "default" config and setup.

YMMV of course, as there are so many factors to consider.