blob: aecc6b291a7a3f28edffa4106c542d9699aa2db9 [file] [log] [blame]
William Kurkianea869482019-04-09 15:16:11 -04001// Copyright 2016 The etcd Authors
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7// http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15package raft
16
17import pb "go.etcd.io/etcd/raft/raftpb"
18
19// ReadState provides state for read only query.
20// It's caller's responsibility to call ReadIndex first before getting
21// this state from ready, it's also caller's duty to differentiate if this
22// state is what it requests through RequestCtx, eg. given a unique id as
23// RequestCtx
24type ReadState struct {
25 Index uint64
26 RequestCtx []byte
27}
28
29type readIndexStatus struct {
30 req pb.Message
31 index uint64
32 acks map[uint64]struct{}
33}
34
35type readOnly struct {
36 option ReadOnlyOption
37 pendingReadIndex map[string]*readIndexStatus
38 readIndexQueue []string
39}
40
41func newReadOnly(option ReadOnlyOption) *readOnly {
42 return &readOnly{
43 option: option,
44 pendingReadIndex: make(map[string]*readIndexStatus),
45 }
46}
47
48// addRequest adds a read only reuqest into readonly struct.
49// `index` is the commit index of the raft state machine when it received
50// the read only request.
51// `m` is the original read only request message from the local or remote node.
52func (ro *readOnly) addRequest(index uint64, m pb.Message) {
53 ctx := string(m.Entries[0].Data)
54 if _, ok := ro.pendingReadIndex[ctx]; ok {
55 return
56 }
57 ro.pendingReadIndex[ctx] = &readIndexStatus{index: index, req: m, acks: make(map[uint64]struct{})}
58 ro.readIndexQueue = append(ro.readIndexQueue, ctx)
59}
60
61// recvAck notifies the readonly struct that the raft state machine received
62// an acknowledgment of the heartbeat that attached with the read only request
63// context.
64func (ro *readOnly) recvAck(m pb.Message) int {
65 rs, ok := ro.pendingReadIndex[string(m.Context)]
66 if !ok {
67 return 0
68 }
69
70 rs.acks[m.From] = struct{}{}
71 // add one to include an ack from local node
72 return len(rs.acks) + 1
73}
74
75// advance advances the read only request queue kept by the readonly struct.
76// It dequeues the requests until it finds the read only request that has
77// the same context as the given `m`.
78func (ro *readOnly) advance(m pb.Message) []*readIndexStatus {
79 var (
80 i int
81 found bool
82 )
83
84 ctx := string(m.Context)
85 rss := []*readIndexStatus{}
86
87 for _, okctx := range ro.readIndexQueue {
88 i++
89 rs, ok := ro.pendingReadIndex[okctx]
90 if !ok {
91 panic("cannot find corresponding read state from pending map")
92 }
93 rss = append(rss, rs)
94 if okctx == ctx {
95 found = true
96 break
97 }
98 }
99
100 if found {
101 ro.readIndexQueue = ro.readIndexQueue[i:]
102 for _, rs := range rss {
103 delete(ro.pendingReadIndex, string(rs.req.Entries[0].Data))
104 }
105 return rss
106 }
107
108 return nil
109}
110
111// lastPendingRequestCtx returns the context of the last pending read only
112// request in readonly struct.
113func (ro *readOnly) lastPendingRequestCtx() string {
114 if len(ro.readIndexQueue) == 0 {
115 return ""
116 }
117 return ro.readIndexQueue[len(ro.readIndexQueue)-1]
118}