public async Task <AppendEntriesResponse> Receive(AppendEntries appendEntries)
{
if (!_serversInClusterInCluster.Contains(appendEntries.LeaderId))
{
AddNewServerToServersInCluster(appendEntries);
}
if (State is Leader)
{
BecomeFollowerAndMatchTerm(appendEntries.Term, appendEntries.LeaderId);
}
_lastAppendEntriesMessageId = appendEntries.MessageId;
// If RPC request or response contains term T > currentTerm:
// set currentTerm = T, convert to follower (§5.1)
if (appendEntries.Term > CurrentTerm || State is Candidate)
{
BecomeFollowerAndMatchTerm(appendEntries.Term, appendEntries.LeaderId);
}
/*
* 1.Reply false if term < currentTerm(�5.1)
*/
if (appendEntries.Term < CurrentTerm)
{
return(new AppendEntriesResponse(CurrentTerm, false, Id, appendEntries.LeaderId));
}
if (appendEntries.Entry == null)
{
//todo heartbeat reset election timer
return(new AppendEntriesResponse(CurrentTerm, true, Id, appendEntries.LeaderId));
}
/*
* 2.Reply false if log doesn�t contain an entry at prevLogIndex
* whose term matches prevLogTerm(�5.3)*/
if (Log.Count > 0 && Log.Count > appendEntries.PreviousLogIndex && Log[appendEntries.PreviousLogIndex].Term != appendEntries.PreviousLogTerm)
{
return(new AppendEntriesResponse(CurrentTerm, false, Id, appendEntries.LeaderId));
}
/* 3.If an existing entry conflicts with a new one(same index
* but different terms), delete the existing entry and all that
* follow it*/
var newEntry = appendEntries.Entry;
if (Log.Count > 0 && Log.Count > appendEntries.PreviousLogIndex)
{
var existingEntry = Log[appendEntries.PreviousLogIndex];
if (existingEntry.Term != newEntry.Term)
{
Log.Remove(existingEntry);
}
}
else if (Log.Count > 0 && Log.Count > appendEntries.PreviousLogIndex + 1)
{
var existingEntry = Log[appendEntries.PreviousLogIndex + 1];
if (existingEntry.Term != newEntry.Term)
{
Log.Remove(existingEntry);
}
}
/* 4.Append any new entries not already in the log
*/
Log.Add(newEntry);
CommitIndex = CommitIndex + 1;
/*
* 5.If leaderCommit > commitIndex, set commitIndex =
* min(leaderCommit, index of last new entry)
*/
if (appendEntries.LeaderCommit > CommitIndex)
{
CommitIndex = Math.Min(appendEntries.LeaderCommit, Log.Count - 1);
}
/* If commitIndex > lastApplied: increment lastApplied, apply
* log[lastApplied] to state machine(§5.3)*/
if (CommitIndex > LastApplied)
{
if (Log.Count > 1)
{
LastApplied++;
}
await _stateMachine.Apply(Log[LastApplied].Command);
return(new AppendEntriesResponse(CurrentTerm, true, Id, appendEntries.LeaderId));
}
return(new AppendEntriesResponse(CurrentTerm, false, Id, appendEntries.LeaderId));
}
