RaftActor doesn't accept RequestVote(lastLogIndex < log.lastLogIndex, lastLogTerm > log.lastLogTerm, ...)

[xirc]

From the Raft thesis (https://github.com/ongardie/dissertation) section 3.6.1 (Election Restriction),
RaftActor should accept RequestVote(lastLogIndex < log.lastLogIndex, lastLogTerm > log.lastLogTerm).

The following is expected:

* RequestVote.lastLogTerm < log.lastLogTerm: deny
* RequestVote.lastLogTerm > log.lastLogTerm:
  * RequestVote.lastLogIndex > log.lastLogIndex: accept
  * RequestVote.lastLogIndex = log.lastLogIndex: accept
  * RequestVote.lastLogIndex < log.lastLogIndex: accept
* RequestVote.lastLogTerm = log.lastLogTerm:
  * RequestVote.lastLogIndex > log.lastLogIndex: accept
  * RequestVote.lastLogIndex = log.lastLogIndex: accept
  * RequestVote.lastLogIndex < log.lastLogIndex: deny

The current implementations are the following:

• Leader:

  akka-entity-replication/src/main/scala/lerna/akka/entityreplication/raft/Leader.scala

  Lines 47 to 51 in c87ff6b

  	case RequestVote(_, term, candidate, lastLogIndex, lastLogTerm)
  	if term.isNewerThan(
  	currentData.currentTerm,
  	) && lastLogTerm >= currentData.replicatedLog.lastLogTerm && lastLogIndex >= currentData.replicatedLog.lastLogIndex =>
  	if (log.isDebugEnabled) log.debug("=== [Leader] accept RequestVote({}, {}) ===", term, candidate)

• Candidate:

  akka-entity-replication/src/main/scala/lerna/akka/entityreplication/raft/Candidate.scala

  Lines 60 to 64 in c87ff6b

  	case RequestVote(_, term, otherCandidate, lastLogIndex, lastLogTerm)
  	if term.isNewerThan(
  	currentData.currentTerm,
  	) && lastLogTerm >= currentData.replicatedLog.lastLogTerm && lastLogIndex >= currentData.replicatedLog.lastLogIndex =>
  	if (log.isDebugEnabled) log.debug("=== [Candidate] accept RequestVote({}, {}) ===", term, otherCandidate)

• Follower:

  akka-entity-replication/src/main/scala/lerna/akka/entityreplication/raft/Follower.scala

  Lines 48 to 50 in c87ff6b

  	case request: RequestVote
  	if request.lastLogTerm < currentData.replicatedLog.lastLogTerm || request.lastLogIndex < currentData.replicatedLog.lastLogIndex =>
  	if (log.isDebugEnabled) log.debug("=== [Follower] deny {} ===", request)