Persistence
Being a peer to peer bus, Zebus cannot rely on a central broker to deliver the messages to a peer that was down when it comes back up. We worked around this problem by creating a Persistence Service, a peer that stores the transmitted messages to replay them to a peer when it comes back up.
During normal operations, a peer transmits a message to a destination peer directly, but it also sends a copy of that message to the persistence peer.
When a message is processed by the destination peer, it sends a message to the Persistence Service to acknowledge the fact that it was processed.
This means that if a message is not processed, for example when a peer is down, it will be stored in the persistence for the time being.