public void EndReceiveInstallSnapshot(FileStream s, InstallSnapshot r)
{
lock (Raft)
{
// 6. If existing log entry has same index and term as snapshot’s
// last included entry, retain log entries following it and reply
var last = ReadLog(r.Argument.LastIncludedIndex);
if (null != last && last.Term == r.Argument.LastIncludedTerm)
{
// 这里全部保留更简单吧，否则如果没有applied，那不就糟了吗？
// RemoveLogReverse(r.Argument.LastIncludedIndex - 1);
return;
}
// 7. Discard the entire log
// 整个删除，那么下一次AppendEnties又会找不到prev。不就xxx了吗?
// 我的想法是，InstallSnapshot 最后一个 trunk 带上 LastIncludedLog，
// 接收者清除log，并把这条日志插入（这个和系统初始化时插入的Index=0的日志道理差不多）。
// 【除了快照最后包含的日志，其他都删除。】
var lastIncludedLog = RaftLog.Decode(r.Argument.LastIncludedLog, Raft.StateMachine.LogFactory);
SaveLog(lastIncludedLog);
// follower 没有并发请求需要处理，在锁内删除。
RemoveLogReverse(lastIncludedLog.Index - 1, FirstIndex);
RemoveLogAndCancelStart(lastIncludedLog.Index + 1, LastIndex);
LastIndex = lastIncludedLog.Index;
FirstIndex = lastIncludedLog.Index;
CommitIndex = FirstIndex;
LastApplied = FirstIndex;
// 8. Reset state machine using snapshot contents (and load
// snapshot’s cluster configuration)
Raft.StateMachine.LoadFromSnapshot(s.Name);
logger.Debug("{0} EndReceiveInstallSnapshot Path={1}", Raft.Name, s.Name);
}
}
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 RaftLog ReadLog(long index)
{
var key = ByteBuffer.Allocate();
key.WriteLong8(index);
var value = Logs.Get(key.Bytes, key.Size);
if (null == value)
{
return(null);
}
return(RaftLog.Decode(new Binary(value), Raft.StateMachine.LogFactory));
}
public LogSequence(Raft raft)
{
Raft = raft;
var options = new DbOptions().SetCreateIfMissing(true);
Rafts = RocksDb.Open(options, Path.Combine(Raft.RaftConfig.DbHome, "rafts"));
{
// Read Term
var termKey = ByteBuffer.Allocate();
termKey.WriteInt(0);
RaftsTermKey = termKey.Copy();
var termValue = Rafts.Get(RaftsTermKey);
if (null != termValue)
{
var bb = ByteBuffer.Wrap(termValue);
Term = bb.ReadLong();
}
else
{
Term = 0;
}
// Read VoteFor
var voteForKey = ByteBuffer.Allocate();
voteForKey.WriteInt(1);
RaftsVoteForKey = voteForKey.Copy();
var voteForvalue = Rafts.Get(RaftsVoteForKey);
if (null != voteForvalue)
{
var bb = ByteBuffer.Wrap(voteForvalue);
VoteFor = bb.ReadString();
}
else
{
VoteFor = string.Empty;
}
}
Logs = RocksDb.Open(options, Path.Combine(Raft.RaftConfig.DbHome, "logs"));
{
// Read Last Log Index
using var itLast = Logs.NewIterator();
itLast.SeekToLast();
if (itLast.Valid())
{
LastIndex = RaftLog.Decode(
new Binary(itLast.Value()),
Raft.StateMachine.LogFactory
).Index;
}
else
{
// empty. add one for prev.
SaveLog(new RaftLog(Term, 0, new HeartbeatLog()));
LastIndex = 0;
}
using var itFirst = Logs.NewIterator();
itFirst.SeekToFirst();
FirstIndex = RaftLog.Decode(
new Binary(itFirst.Value()),
Raft.StateMachine.LogFactory
).Index;
// 【注意】snapshot 以后 FirstIndex 会推进，不再是从0开始。
LastApplied = FirstIndex;
CommitIndex = FirstIndex;
}
}