App session data

When your application has one instance, it’s generally safe to use the default session storage, which is the local file system. You can only see problems if your single instance crashes, the local file system goes away, and you lose your sessions. For many applications, this works just fine, but you need to consider how this affects your application.

If you have multiple application instances or you need a more robust solution for your application, use Redis or Memcached as a backup store for your session data. The buildpack supports both backups and when one is bound to your application, it detects it and configures PHP to use it for session storage.

By default, there is no configuration necessary. To create a Redis or Memcached service, ensure that the service name contains redis-sessions or memcached-sessions and then bind the service to the application.

Example:

$ cf create-service redis some-plan app-redis-sessions
$ cf bind-service app app-redis-sessions
$ cf restage app

If you want to use a specific service instance or change the search key, you can set either REDIS_SESSION_STORE_SERVICE_NAME or MEMCACHED_SESSION_STORE_SERVICE_NAME in .bp-config/options.json to the new search key. The session configuration extension searches the bound services by name for the new session key.

Configuration changes

When detected, the following changes are made:

Redis

the redis PHP extension is installed, which provides the session save handler
session.name is set to PHPSESSIONID which deactivates sticky sessions
session.save_handler is configured to redis
session.save_path is configured based on the bound credentials, for example tcp://host:port?auth=pass

Memcached

the memcached PHP extension is installed, which provides the session save handler
session.name is set to PHPSESSIONID which deactivates sticky sessions
session.save_handler is configured to memcached
session.save_path is configured based on the bound credentials (i.e. PERSISTENT=app_sessions host:port)
memcached.sess_binary is set to On
memcached.use_sasl is set to On, which enables authentication
memcached.sess_sasl_username and memcached.sess_sasl_password are set with the service credentials