splent_feature_session_redis

Server-side sessions in Redis for SPLENT products, through Flask-Session (config archetype). It is one of the session backends a product picks from; splent_feature_session_filesystem is the other. It requires splent_feature_redis, which runs the Redis server and says how to reach it.

What it does

When the app starts it sets Flask-Session to keep sessions in Redis:

• SESSION_TYPE = "redis" and SESSION_REDIS, a client for REDIS_SESSION_URL: the server splent_feature_redis configures, with its password, on the database it keeps for sessions. Tasks and anything else stored in Redis live in other databases, so they never mix with sessions.
• SESSION_PERMANENT = False, so a session ends with the browser unless a feature asks for more.
• SESSION_KEY_PREFIX = "<product>:" and SESSION_COOKIE_NAME = "<product>_session", taken from SPLENT_APP. Two products served from the same host share cookies and may share one Redis, and the prefix and the cookie name keep their sessions apart.

Configuration

Where the sessions live is splent_feature_redis's to decide, so it is configured there: REDIS_URL, REDIS_PASSWORD and REDIS_SESSION_DB. This feature reads the result from app.config, never from the environment.

With neither URL in the configuration the app does not start, and the error names the missing feature. A guessed default would only move the failure to the first request.

Tests

splent feature:test splent_feature_session_redis

The unit tests run inject_config against a bare Flask app with a mocked Redis client, so no server is needed. One runs splent_feature_redis's inject_config first, with the sessions on a database other than 0, so the two features cannot disagree on a key name without a test failing. Against a splent_feature_redis without a database per use (1.5), it is skipped.