goupr is Go implementation of couchbase UPR protocol for cluster replication and failover, and right now it implements the client (consumer) side of UPR protocol.

Basic design:

Applications Connect() with producer (server) and initiates a session with the producer. Connect() returns a reference to Client instance back to the application.

Using the client instance, application can create one or more Stream on the same connection by calling client.UprStream(). Every stream is uniquely identified by the opaque-id supplied during stream creation. A map of opaque-id and Stream reference is maintained by the Client instance.

Every connection also spawns a goroutine to handle all incoming messages from the server. If the messages are mapped to stream instance, then those messages are sent to the corresponding stream's channel, else they are sent to a common response channel (maintained per connection).

Known bugs:

• when application first call UprStream() to open more than one stream, supplying an stream-event channel to receive mutation, MUTATIONS received from previously opened stream can block on application's stream-event channel and not receive response for the last call to UprStream(). Leading to a deadlock. Right now, we are avoiding this by encouraging the application to call UprStream in a separate go-routine.