Roadmap

I am planning to work on the following tasks in the future, but have no strict plans about their timeline. If you have ideas, just chime in!

• Opt-in deduplication mechanism via implementation of the Implementing Linearizability at Large Scale and Low Latency paper. Currently, one can implement deduplication inside his custom StateMachine implementation. I would like to offer a generic and opt-in solution by MicroRaft.

• Witness replicas possibly via implementation of the Pirogue, a lighter dynamic version of the Raft distributed consensus algorithm paper. Witness replicas participate in quorum calculations but do not keep any state for StateMachine to reduce the storage overhead. When a follower fails, a witness replica can be promoted to the follower role to increase the number of StateMachine replicas.

• Offload more work from leader to followers. One candidate is transfer of committed log entries. Just like parallel snapshot chunk transfer from followers, a slow follower can get committed log entries from followers.

• Improve the log replication design. The current log replication design is quite solid but there is still room for improvement. One idea is, once a follower installs a snapshot, the leader can boost that follower by increasing its Append Entries RPC batch size, so that it catches up with the majority faster. Another thing to try is, currently when a leader sends an Append Entries RPC to a follower, it does not send another RPC to that follower either until the follower sends a response, or the Append Entries RPC backoff timeout elapses. During this duration, the leader might append new log entries in its local log. During the Append Entries RPC backoff is enabled for a follower, if more log entries are appended to the leader's log, a few of these log entries can be also sent to the follower.