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raft: cleanup read index code (#11528)

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Signed-off-by: qupeng <qupeng@pingcap.com>
This commit is contained in:
qupeng 2020-03-04 01:20:25 +08:00 committed by GitHub
parent 3f4f7c5a6c
commit 6f850a65a1
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1 changed files with 50 additions and 35 deletions
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85
raft/raft.go
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@ -1078,39 +1078,34 @@ func stepLeader(r *raft, m pb.Message) error {
r.bcastAppend()
return nil
case pb.MsgReadIndex:
// If more than the local vote is needed, go through a full broadcast,
// otherwise optimize.
if !r.prs.IsSingleton() {
if r.raftLog.zeroTermOnErrCompacted(r.raftLog.term(r.raftLog.committed)) != r.Term {
// Reject read only request when this leader has not committed any log entry at its term.
return nil
}
// thinking: use an interally defined context instead of the user given context.
// We can express this in terms of the term and index instead of a user-supplied value.
// This would allow multiple reads to piggyback on the same message.
switch r.readOnly.option {
case ReadOnlySafe:
r.readOnly.addRequest(r.raftLog.committed, m)
// The local node automatically acks the request.
r.readOnly.recvAck(r.id, m.Entries[0].Data)
r.bcastHeartbeatWithCtx(m.Entries[0].Data)
case ReadOnlyLeaseBased:
ri := r.raftLog.committed
if m.From == None || m.From == r.id { // from local member
r.readStates = append(r.readStates, ReadState{Index: ri, RequestCtx: m.Entries[0].Data})
} else {
r.send(pb.Message{To: m.From, Type: pb.MsgReadIndexResp, Index: ri, Entries: m.Entries})
}
}
} else { // only one voting member (the leader) in the cluster
if m.From == None || m.From == r.id { // from leader itself
r.readStates = append(r.readStates, ReadState{Index: r.raftLog.committed, RequestCtx: m.Entries[0].Data})
} else { // from learner member
r.send(pb.Message{To: m.From, Type: pb.MsgReadIndexResp, Index: r.raftLog.committed, Entries: m.Entries})
// only one voting member (the leader) in the cluster
if r.prs.IsSingleton() {
if resp := r.responseToReadIndexReq(m, r.raftLog.committed); resp.To != None {
r.send(resp)
}
return nil
}
// Reject read only request when this leader has not committed any log entry at its term.
if !r.committedEntryInCurrentTerm() {
return nil
}
// thinking: use an interally defined context instead of the user given context.
// We can express this in terms of the term and index instead of a user-supplied value.
// This would allow multiple reads to piggyback on the same message.
switch r.readOnly.option {
// If more than the local vote is needed, go through a full broadcast.
case ReadOnlySafe:
r.readOnly.addRequest(r.raftLog.committed, m)
// The local node automatically acks the request.
r.readOnly.recvAck(r.id, m.Entries[0].Data)
r.bcastHeartbeatWithCtx(m.Entries[0].Data)
case ReadOnlyLeaseBased:
if resp := r.responseToReadIndexReq(m, r.raftLog.committed); resp.To != None {
r.send(resp)
}
}
return nil
}
@ -1200,11 +1195,8 @@ func stepLeader(r *raft, m pb.Message) error {
rss := r.readOnly.advance(m)
for _, rs := range rss {
req := rs.req
if req.From == None || req.From == r.id { // from local member
r.readStates = append(r.readStates, ReadState{Index: rs.index, RequestCtx: req.Entries[0].Data})
} else {
r.send(pb.Message{To: req.From, Type: pb.MsgReadIndexResp, Index: rs.index, Entries: req.Entries})
if resp := r.responseToReadIndexReq(rs.req, rs.index); resp.To != None {
r.send(resp)
}
}
case pb.MsgSnapStatus:
@ -1601,6 +1593,29 @@ func (r *raft) abortLeaderTransfer() {
r.leadTransferee = None
}
// committedEntryInCurrentTerm return true if the peer has committed an entry in its term.
func (r *raft) committedEntryInCurrentTerm() bool {
return r.raftLog.zeroTermOnErrCompacted(r.raftLog.term(r.raftLog.committed)) == r.Term
}
// responseToReadIndexReq constructs a response for `req`. If `req` comes from the peer
// itself, a blank value will be returned.
func (r *raft) responseToReadIndexReq(req pb.Message, readIndex uint64) pb.Message {
if req.From == None || req.From == r.id {
r.readStates = append(r.readStates, ReadState{
Index: readIndex,
RequestCtx: req.Entries[0].Data,
})
return pb.Message{}
}
return pb.Message{
Type: pb.MsgReadIndexResp,
To: req.From,
Index: readIndex,
Entries: req.Entries,
}
}
// increaseUncommittedSize computes the size of the proposed entries and
// determines whether they would push leader over its maxUncommittedSize limit.
// If the new entries would exceed the limit, the method returns false. If not,