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);
}
}
private void InstallSnapshot(string path, Server.ConnectorEx connector)
{
// 整个安装成功结束时设置。中间Break(return)不设置。
// 后面 finally 里面使用这个标志
bool InstallSuccess = false;
logger.Debug("{0} InstallSnapshot Start... Path={1} ToConnector={2}",
Raft.Name, path, connector.Name);
try
{
var snapshotFile = new FileStream(path, FileMode.Open);
long offset = 0;
var buffer = new byte[32 * 1024];
var FirstLog = ReadLog(FirstIndex);
var trunkArg = new InstallSnapshotArgument();
trunkArg.Term = Term;
trunkArg.LeaderId = Raft.LeaderId;
trunkArg.LastIncludedIndex = FirstLog.Index;
trunkArg.LastIncludedTerm = FirstLog.Term;
while (!trunkArg.Done && Raft.IsLeader)
{
int rc = snapshotFile.Read(buffer);
trunkArg.Offset = offset;
trunkArg.Data = new Binary(buffer, 0, rc);
trunkArg.Done = rc < buffer.Length;
offset += rc;
if (trunkArg.Done)
{
trunkArg.LastIncludedLog = new Binary(FirstLog.Encode());
}
while (Raft.IsLeader)
{
connector.HandshakeDoneEvent.WaitOne();
var future = new TaskCompletionSource <int>();
var r = new InstallSnapshot()
{
Argument = trunkArg
};
if (!r.Send(connector.Socket,
(_) =>
{
future.SetResult(0);
return(Procedure.Success);
}))
{
continue;
}
future.Task.Wait();
if (r.IsTimeout)
{
continue;
}
lock (Raft)
{
if (this.TrySetTerm(r.Result.Term))
{
// new term found.
Raft.ConvertStateTo(Raft.RaftState.Follower);
return;
}
}
switch (r.ResultCode)
{
case global::Zeze.Raft.InstallSnapshot.ResultCodeNewOffset:
break;
default:
logger.Warn($"InstallSnapshot Break ResultCode={r.ResultCode}");
return;
}
if (r.Result.Offset >= 0)
{
if (r.Result.Offset > snapshotFile.Length)
{
logger.Error($"InstallSnapshot.Result.Offset Too Big.{r.Result.Offset}/{snapshotFile.Length}");
return; // 中断安装。
}
offset = r.Result.Offset;
snapshotFile.Seek(offset, SeekOrigin.Begin);
}
break;
}
}
InstallSuccess = Raft.IsLeader;
logger.Debug("{0} InstallSnapshot [SUCCESS] Path={1} ToConnector={2}",
Raft.Name, path, connector.Name);
}
finally
{
lock (Raft)
{
connector.InstallSnapshotting = false;
InstallSnapshotting.Remove(connector.Name);
if (InstallSuccess)
{
// 安装完成，重新初始化，使得以后的AppendEnties能继续工作。
// = FirstIndex + 1，防止Index跳着分配，使用ReadLogStart。
var next = ReadLogStart(FirstIndex + 1);
connector.NextIndex = next == null ? FirstIndex + 1 : next.Index;
}
}
}
}
