Purpose of Redis

Redis is an in-memory data structure store and is used as a database, cache, and message broker. Redis functions as an in-memory cache for Cherwell server farms.

By connecting every web server to the same Redis, the applications can share state and collaborate. When a server performs an operation, it saves the state of the current user or application to Redis. In a scenario where a user is bounced from one server to the another, each server can pick up from where the previous server left off by retrieving the latest state from Redis.

For a Cherwell Application Server, the cost of synchronizing with Redis is minimal because the Application Server exchanges a limited amount of information with Redis. For a Cherwell web server, Internet Information Services (IIS) holds state for each user in form of session, and it can reach the size of a few MB (3-5 MB is the typical size). For every web request going from the Cherwell web application to the server, there is an exchange of session state twice with Redis:
  • When the request starts, to retrieve session from Redis.
  • When the request ends, to save session to Redis.

For more information and support, refer to Redis.Io.