Sessions

A user of your bot can be in any single flow and state at any given moment. They can never be in more than one flow or state. For this reason, Stealth sessions are modeled using finite state machines.

Hierarchical Finite State Machines

Technically, each flow is its own state machine with its own states. Stealth, however, does not restrict the movement between states as rigidly. So while we find the state machine model helpful to learn sessions, don't spend too much time on Wikipedia!

Redis Backed Sessions

User sessions are stored in Redis. Each session is a lightweight key-value pair. The key is the user's ID from the service -- so for Facebook it may be a long integer value: 100023838288224423. The value is the flow and state for the user separated by a "stabby" operator (->).

So if for example a user with ID 100023838288224423 is currently at the hello flow and ask_name state, the value for the key would be: hello->ask_name.

You likely won't be interacting with sessions directly since Stealth manages it automatically for you. We just present it here for clarity into how sessions work.

Session Expiration

By default, Stealth will not expire your user sessions. If you want your sessions to expire, you can set the session_ttl option:

Stealth.config.session_ttl = 2_592_000 # seconds (30 * 24 * 60 * 60)

The above configuration setting will result in stale keys expiring in 30 days. Sessions that have been accessed reset the TTL (time to live). If you set a value of zero (the default), session expiration will be disabled.

If a user returns to your bot after their session has expired, they will start again in the Hello flow or whatever you have defined to be your first flow.