private int ProcessRequestVoteResult(RequestVote rpc, Connector c)
{
lock (this)
{
if (LogSequence.TrySetTerm(rpc.Result.Term))
{
// new term found
ConvertStateTo(RaftState.Follower);
return(Procedure.Success);
}
}
if (rpc.Result.VoteGranted && VoteSuccess.TryAdd(c.Name, c))
{
lock (this)
{
if (
// 确保当前状态是选举中。没有判断这个，
// 后面 ConvertStateTo 也会忽略不正确的状态转换。
State == RaftState.Candidate
// 加上自己就是多数派了。
&& VoteSuccess.Count >= RaftConfig.HalfCount)
{
ConvertStateTo(RaftState.Leader);
}
}
}
return(Procedure.Success);
}
private int ProcessRequestVote(Protocol p)
{
lock (this)
{
var r = p as RequestVote;
if (LogSequence.TrySetTerm(r.Argument.Term))
{
// new term found.
ConvertStateTo(RaftState.Follower);
}
// else continue process
r.Result.Term = LogSequence.Term;
// RequestVote RPC
// Receiver implementation:
// 1.Reply false if term < currentTerm(§5.1)
// 2.If votedFor is null or candidateId, and candidate’s log is at
// least as up - to - date as receiver’s log, grant vote(§5.2, §5.4)
r.Result.VoteGranted = (r.Argument.Term >= LogSequence.Term) &&
LogSequence.CanVoteFor(r.Argument.CandidateId) &&
IsLastLogUpToDate(r.Argument.LastLogTerm, r.Argument.LastLogIndex);
if (r.Result.VoteGranted)
{
LogSequence.SetVoteFor(r.Argument.CandidateId);
}
logger.Debug("{0}: VoteFor={1} Rpc={2}", Name, LogSequence.VoteFor, r);
r.SendResultCode(0);
return(Procedure.Success);
}
}
private void SendRequestVote(SchedulerTask ThisTask)
{
lock (this)
{
VoteSuccess.Clear(); // 每次选举开始清除。
LeaderId = string.Empty;
LogSequence.SetVoteFor(Name); // Vote Self First.
LogSequence.TrySetTerm(LogSequence.Term + 1);
WaitMajorityVoteTimoutTask?.Cancel();
WaitMajorityVoteTimoutTask = null;
var arg = new RequestVoteArgument();
arg.Term = LogSequence.Term;
arg.CandidateId = Name;
var log = LogSequence.LastRaftLog();
arg.LastLogIndex = log.Index;
arg.LastLogTerm = log.Term;
Server.Config.ForEachConnector(
(c) =>
{
if (false == c.IsHandshakeDone)
{
return;
}
var rpc = new RequestVote()
{
Argument = arg
};
rpc.Send(c.Socket, (p) => ProcessRequestVoteResult(rpc, c));
logger.Debug("{0}: SendRequestVote {1}", Name, rpc);
});
// 定时，如果超时选举还未完成，再次发起选举。
WaitMajorityVoteTimoutTask = Scheduler.Instance.Schedule(
(ThisTask) =>
{
lock (this)
{
StartRequestVoteDelayTask = null;
ConvertStateTo(RaftState.Candidate);
}
},
RaftConfig.AppendEntriesTimeout + 1000);
}
}
private int ProcessAppendEntries(Protocol p)
{
var r = p as AppendEntries;
lock (this)
{
LogSequence.TrySetTerm(r.Argument.Term);
// 【注意】只有Leader会发送AppendEntries，总是转到Follower，不管当前状态。
// raft.pdf 文档描述仅在 Candidate 才转。
if (State != RaftState.Follower)
{
ConvertStateTo(RaftState.Follower);
}
LeaderId = r.Argument.LeaderId; // always replace
return(LogSequence.FollowerOnAppendEntries(r));
}
}
private int ProcessInstallSnapshot(Protocol p)
{
var r = p as InstallSnapshot;
lock (this)
{
if (LogSequence.TrySetTerm(r.Argument.Term))
{
LeaderId = r.Argument.LeaderId;
// new term found.
ConvertStateTo(RaftState.Follower);
}
}
r.Result.Term = LogSequence.Term;
if (r.Argument.Term < LogSequence.Term)
{
// 1. Reply immediately if term < currentTerm
r.SendResultCode(InstallSnapshot.ResultCodeTermError);
return(Procedure.LogicError);
}
// 2. Create new snapshot file if first chunk(offset is 0)
// 把 LastIncludedIndex 放到文件名中，
// 新的InstallSnapshot不覆盖原来进行中或中断的。
var path = Path.Combine(RaftConfig.DbHome,
$"{LogSequence.SnapshotFileName}.{r.Argument.LastIncludedIndex}");
FileStream outputFileStream = null;
if (r.Argument.Offset == 0)
{
// GetOrAdd 允许重新开始。
outputFileStream = ReceiveSnapshotting.GetOrAdd(
r.Argument.LastIncludedIndex,
(_) => new FileStream(path, FileMode.OpenOrCreate));
outputFileStream.Seek(0, SeekOrigin.End);
}
else
{
// ignore return of TryGetValue here.
ReceiveSnapshotting.TryGetValue(r.Argument.LastIncludedIndex, out outputFileStream);
}
if (null == outputFileStream)
{
// 肯定是旧的被丢弃的安装，Discard And Ignore。
r.SendResultCode(InstallSnapshot.ResultCodeOldInstall);
return(Procedure.Success);
}
r.Result.Offset = -1; // 默认让Leader继续传输，不用重新定位。
if (r.Argument.Offset > outputFileStream.Length)
{
// 数据块超出当前已经接收到的数据。
// 填写当前长度，让Leader从该位置开始重新传输。
r.Result.Offset = outputFileStream.Length;
r.SendResultCode(InstallSnapshot.ResultCodeNewOffset);
return(Procedure.Success);
}
if (r.Argument.Offset == outputFileStream.Length)
{
// 正常的Append流程，直接写入。
// 3. Write data into snapshot file at given offset
outputFileStream.Write(r.Argument.Data.Bytes, r.Argument.Data.Offset, r.Argument.Data.Count);
}
else
{
// 数据块开始位置小于当前长度。
var newEndPosition = r.Argument.Offset + r.Argument.Data.Count;
if (newEndPosition > outputFileStream.Length)
{
// 有新的数据需要写入文件。
outputFileStream.Seek(r.Argument.Offset, SeekOrigin.Begin);
outputFileStream.Write(r.Argument.Data.Bytes, r.Argument.Data.Offset, r.Argument.Data.Count);
}
r.Result.Offset = outputFileStream.Length;
}
// 4. Reply and wait for more data chunks if done is false
if (r.Argument.Done)
{
// 5. Save snapshot file, discard any existing or partial snapshot with a smaller index
outputFileStream.Close();
foreach (var e in ReceiveSnapshotting)
{
if (e.Key < r.Argument.LastIncludedIndex)
{
e.Value.Close();
var pathDelete = Path.Combine(RaftConfig.DbHome, $"{LogSequence.SnapshotFileName}.{e.Key}");
File.Delete(path);
ReceiveSnapshotting.TryRemove(e.Key, out var _);
}
}
// 剩下的处理流程在下面的函数里面。
LogSequence.EndReceiveInstallSnapshot(outputFileStream, r);
}
r.SendResultCode(0);
return(Procedure.Success);
}