Distributed Caching System

The system consists of three main components: Source End, Client End, and Center.

• Source End: Responsible for storing business data. When data changes, it notifies the Center about which keys have been updated.
• Client End: The consumer of data. Each client maintains a "consensus-in-progress" status for each key.
  • When this state is active, the client queries the Center on every data access to check if consensus has been reached.
  • If not, it uses the previous cached data.
  • If consensus has been reached, the client uses the new data, and the first client to do so updates the Center's data.
• Center: Receives requests from clients and:
  • Checks if its local cache is stale (dirty). If it is, returns an empty response.
  • If the local cache is not stale, returns the current cached value.
  • When receiving update notifications from the Source End, waits for consensus with all clients to ensure everyone agrees on the updated state.
  • During consensus period, local cache remains in its current state (invalid or valid).
  • Returns current cached data to client requests during this period.
  • Only when consensus is reached does the Center update its local cache to reflect the new state.