A Kotlin multiplatform Raft consensus implementation base on:
- immutability in order to be functional friendly,
- an agnostic network layer,
- an event based approach suitable for an implementation with actors and
- an agnostic database layer i.e. based on abstract command execution.
The NodeKind denotes the behaviors linked to a node. We have:
- an Elector i.e. a Follower without a Leader in the Raft specification
- a Candidate
- a Follower and
- a Leader.
Each oriented arrow is defined by:
- a message,
- a condition if necessary and
- a set of reactions to be performed by the system.
For instance, when an Elector accepts a RequestVote message it becomes a Follower, and an AcceptVote reaction should be performed. This reaction highlights the acceptance to be send to the corresponding Candidate. This AcceptVote is managed by a Candidate node.
TimeOut | ArmElectionTimeOut
+-------------------------------------------------------------------------+
| |
v RequestVote | AcceptVote | |
+-> Elector ------------------------------------------------------------+ |
| | | |
| | TimeOut | ArmElectionTimeOut StartElection v |
| V Follower ---+
+–- Candidate <-+ |
Higher | | | | TimeOut | ArmElection TimeOut StartElection +--------+
Term | | | | AcceptVote if No Quorum |
| | +---+ |
| | |
| | AcceptVote if Quorum | ArmHeartBeatTime SynchronizeLog InsertMarkInLog |
| V |
+-- Leader <-+ |
| | | TimeOut | ArmHeartBeatTime SynchronizeLog |
| +---+ |
+--------------------------------------------------------------------------------+
Things to be done:
- a proof of this implementation
- a client
insertmethod conforming to the specification - the log compaction
- use IO monads for database evolution for instance
- ...
GNU LESSER GENERAL PUBLIC LICENSE
Version 2.1, February 1999
Copyright (C) 1991, 1999 Free Software Foundation, Inc.
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