119 lines
3.3 KiB
Go
119 lines
3.3 KiB
Go
// Copyright 2016 The etcd Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package raft
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import pb "go.etcd.io/etcd/raft/raftpb"
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// ReadState provides state for read only query.
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// It's caller's responsibility to call ReadIndex first before getting
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// this state from ready, it's also caller's duty to differentiate if this
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// state is what it requests through RequestCtx, eg. given a unique id as
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// RequestCtx
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type ReadState struct {
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Index uint64
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RequestCtx []byte
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}
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type readIndexStatus struct {
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req pb.Message
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index uint64
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acks map[uint64]struct{}
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}
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type readOnly struct {
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option ReadOnlyOption
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pendingReadIndex map[string]*readIndexStatus
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readIndexQueue []string
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}
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func newReadOnly(option ReadOnlyOption) *readOnly {
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return &readOnly{
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option: option,
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pendingReadIndex: make(map[string]*readIndexStatus),
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}
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}
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// addRequest adds a read only reuqest into readonly struct.
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// `index` is the commit index of the raft state machine when it received
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// the read only request.
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// `m` is the original read only request message from the local or remote node.
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func (ro *readOnly) addRequest(index uint64, m pb.Message) {
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ctx := string(m.Entries[0].Data)
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if _, ok := ro.pendingReadIndex[ctx]; ok {
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return
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}
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ro.pendingReadIndex[ctx] = &readIndexStatus{index: index, req: m, acks: make(map[uint64]struct{})}
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ro.readIndexQueue = append(ro.readIndexQueue, ctx)
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}
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// recvAck notifies the readonly struct that the raft state machine received
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// an acknowledgment of the heartbeat that attached with the read only request
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// context.
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func (ro *readOnly) recvAck(m pb.Message) int {
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rs, ok := ro.pendingReadIndex[string(m.Context)]
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if !ok {
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return 0
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}
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rs.acks[m.From] = struct{}{}
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// add one to include an ack from local node
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return len(rs.acks) + 1
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}
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// advance advances the read only request queue kept by the readonly struct.
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// It dequeues the requests until it finds the read only request that has
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// the same context as the given `m`.
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func (ro *readOnly) advance(m pb.Message) []*readIndexStatus {
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var (
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i int
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found bool
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)
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ctx := string(m.Context)
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rss := []*readIndexStatus{}
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for _, okctx := range ro.readIndexQueue {
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i++
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rs, ok := ro.pendingReadIndex[okctx]
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if !ok {
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panic("cannot find corresponding read state from pending map")
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}
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rss = append(rss, rs)
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if okctx == ctx {
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found = true
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break
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}
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}
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if found {
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ro.readIndexQueue = ro.readIndexQueue[i:]
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for _, rs := range rss {
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delete(ro.pendingReadIndex, string(rs.req.Entries[0].Data))
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}
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return rss
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}
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return nil
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}
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// lastPendingRequestCtx returns the context of the last pending read only
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// request in readonly struct.
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func (ro *readOnly) lastPendingRequestCtx() string {
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if len(ro.readIndexQueue) == 0 {
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return ""
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}
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return ro.readIndexQueue[len(ro.readIndexQueue)-1]
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}
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