Accessing session data

Session data in GitLab is stored in Redis and can be accessed in a variety of ways.

During a web request, for example:

  • Rails provides access to the session from within controllers through ActionDispatch::Session.
  • Outside of controllers, it is possible to access the session through Gitlab::Session.

Outside of a web request it is still possible to access sessions stored in Redis. For example:

  • Session IDs and contents can be looked up directly in Redis.
  • Data about the UserAgent associated with the session can be accessed through ActiveSession.

When storing values in a session it is best to:

  • Use simple primitives and avoid storing objects to avoid marshaling complications.
  • Clean up after unneeded variables to keep memory usage in Redis down.

GitLab::Session

Sometimes you might want to persist data in the session instead of another store like the database. Gitlab::Session lets you access this without passing the session around extensively. For example, you could access it from within a policy without having to pass the session through to each place permissions are checked from.

The session has a hash-like interface, just like when using it from a controller. There is also NamespacedSessionStore for storing key-value data in a hash. 

# Lookup a value stored in the current session
Gitlab::Session.current[:my_feature]

# Modify the current session stored in redis
Gitlab::Session.current[:my_feature] = value

# Store key-value data namespaced under a key
Gitlab::NamespacedSessionStore.new(:my_feature)[some_key] = value

# Set the session for a block of code, such as for tests
Gitlab::Session.with_session(my_feature: value) do
  # Code that uses Session.current[:my_feature]
end

Redis

Session data can be accessed directly through Redis. This can let you check up on a browser session when debugging. 

# Get a list of sessions
session_ids = Gitlab::Redis::Sessions.with do |redis|
  redis.smembers("#{Gitlab::Redis::Sessions::USER_SESSIONS_LOOKUP_NAMESPACE}:#{user.id}")
end

# Retrieve a specific session
session_data = Gitlab::Redis::Sessions.with { |redis| redis.get("#{Gitlab::Redis::Sessions::SESSION_NAMESPACE}:#{session_id}") }
Marshal.load(session_data)

Getting device information with ActiveSession

The Active Sessions page on a user’s profile displays information about the device used to access each session. The methods used there to list sessions can also be useful for development. 

# Get list of sessions for a given user
# Includes session_id and data from the UserAgent
ActiveSession.list(user)