internal int FollowerOnAppendEntries(AppendEntries r)
{
LeaderActiveTime = Zeze.Util.Time.NowUnixMillis;
r.Result.Term = Term;
r.Result.Success = false; // set default false
if (r.Argument.Term < Term)
{
// 1. Reply false if term < currentTerm (§5.1)
r.SendResult();
return(Procedure.LogicError);
}
var prevLog = ReadLog(r.Argument.PrevLogIndex);
if (prevLog == null || prevLog.Term != r.Argument.PrevLogTerm)
{
// 2. Reply false if log doesn’t contain an entry
// at prevLogIndex whose term matches prevLogTerm(§5.3)
r.SendResult();
return(Procedure.LogicError);
}
foreach (var raftLogData in r.Argument.Entries)
{
var copyLog = RaftLog.Decode(raftLogData, Raft.StateMachine.LogFactory);
var conflictCheck = ReadLog(copyLog.Index);
if (null != conflictCheck)
{
if (conflictCheck.Term != copyLog.Term)
{
// 3. If an existing entry conflicts
// with a new one (same index but different terms),
// delete the existing entry and all that follow it(§5.3)
// raft.pdf 5.3
RemoveLogAndCancelStart(conflictCheck.Index, LastIndex);
LastIndex = prevLog.Index;
}
}
else
{
// 4. Append any new entries not already in the log
SaveLog(copyLog);
}
// 复用这个变量。当冲突需要删除时，精确指到前一个日志。
prevLog = copyLog;
}
// 5. If leaderCommit > commitIndex,
// set commitIndex = min(leaderCommit, index of last new entry)
if (r.Argument.LeaderCommit > CommitIndex)
{
CommitIndex = Math.Min(r.Argument.LeaderCommit, LastRaftLog().Index);
TryApply(ReadLog(CommitIndex));
}
r.Result.Success = true;
logger.Debug("{0}: {1}", Raft.Name, r);
r.SendResultCode(0);
return(Procedure.Success);
}
private void TrySendAppendEntries(Server.ConnectorEx connector, AppendEntries pending)
{
lock (Raft)
{
// 按理说，多个Follower设置一次就够了，这里就不做这个处理了。
AppendLogActiveTime = Util.Time.NowUnixMillis;
if (connector.Pending != pending)
{
return;
}
// 先清除，下面中断(return)不用每次自己清除。
connector.Pending = null;
if (false == connector.IsHandshakeDone)
{
// Hearbeat Will Retry
return;
}
// 【注意】
// 正在安装Snapshot，此时不复制日志，肯定失败。
// 不做这个判断也是可以工作的，算是优化。
if (connector.InstallSnapshotting)
{
return;
}
if (connector.NextIndex > LastIndex)
{
return;
}
var nextLog = ReadLogReverse(connector.NextIndex);
if (nextLog.Index == FirstIndex)
{
// 已经到了日志开头，此时不会有prev-log，无法复制日志了。
// 这一般发生在Leader进行了Snapshot，但是Follower的日志还更老。
// 新起的Follower也一样。
StartInstallSnapshot(connector);
return;
}
// 现在Index总是递增，但没有确认步长总是为1，这样能处理不为1的情况。
connector.NextIndex = nextLog.Index;
connector.Pending = new AppendEntries();
connector.Pending.Argument.Term = Term;
connector.Pending.Argument.LeaderId = Raft.Name;
connector.Pending.Argument.LeaderCommit = CommitIndex;
// 肯定能找到的。
var prevLog = ReadLogReverse(nextLog.Index - 1);
connector.Pending.Argument.PrevLogIndex = prevLog.Index;
connector.Pending.Argument.PrevLogTerm = prevLog.Term;
// 限制一次发送的日志数量，【注意】这个不是raft要求的。
int maxCount = Raft.RaftConfig.MaxAppendEntiresCount;
RaftLog lastCopyLog = nextLog;
for (var copyLog = nextLog;
maxCount > 0 && null != copyLog && copyLog.Index <= LastIndex;
copyLog = ReadLogStart(copyLog.Index + 1), --maxCount
)
{
lastCopyLog = copyLog;
connector.Pending.Argument.Entries.Add(new Binary(copyLog.Encode()));
}
connector.Pending.Argument.LastEntryIndex = lastCopyLog.Index;
if (false == connector.Pending.Send(
connector.Socket,
(p) => ProcessAppendEntriesResult(connector, p),
Raft.RaftConfig.AppendEntriesTimeout))
{
connector.Pending = null;
// Hearbeat Will Retry
}
}
}