mirror of
https://github.com/etcd-io/etcd.git
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0f9d7a4f95
This commit makes the rarely used `raftpb.Message.Snapshot` field nullable. In doing so, it reduces the memory size of a `raftpb.Message` message from 264 bytes to 128 bytes — a 52% reduction in size. While this commit does not change the protobuf encoding, it does change how that encoding is used. `(gogoproto.nullable) = false` instruct the generated proto marshaling logic to always encode a value for the field, even if that value is empty. `(gogoproto.nullable) = true` instructs the generated proto marshaling logic to omit an encoded value for the field if the field is nil. This raises compatibility concerns in both directions. Messages encoded by new binary versions without a `Snapshot` field will be decoded as an empty field by old binary versions. In other words, old binary versions can't tell the difference. However, messages encoded by old binary versions with an empty Snapshot field will be decoded as a non-nil, empty field by new binary versions. As a result, new binary versions need to be prepared to handle such messages. While Message.Snapshot is not intentionally part of the external interface of this library, it was possible for users of the library to access it and manipulate it. As such, this change may be considered a breaking change. Signed-off-by: Nathan VanBenschoten <nvanbenschoten@gmail.com>
88 lines
2.5 KiB
Go
88 lines
2.5 KiB
Go
// Copyright 2015 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 etcdserver
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import (
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"io"
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"go.etcd.io/etcd/raft/v3/raftpb"
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"go.etcd.io/etcd/server/v3/etcdserver/api/snap"
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"go.etcd.io/etcd/server/v3/storage/backend"
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humanize "github.com/dustin/go-humanize"
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"go.uber.org/zap"
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)
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// createMergedSnapshotMessage creates a snapshot message that contains: raft status (term, conf),
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// a snapshot of v2 store inside raft.Snapshot as []byte, a snapshot of v3 KV in the top level message
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// as ReadCloser.
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func (s *EtcdServer) createMergedSnapshotMessage(m raftpb.Message, snapt, snapi uint64, confState raftpb.ConfState) snap.Message {
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lg := s.Logger()
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// get a snapshot of v2 store as []byte
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clone := s.v2store.Clone()
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d, err := clone.SaveNoCopy()
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if err != nil {
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lg.Panic("failed to save v2 store data", zap.Error(err))
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}
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// commit kv to write metadata(for example: consistent index).
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s.KV().Commit()
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dbsnap := s.be.Snapshot()
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// get a snapshot of v3 KV as readCloser
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rc := newSnapshotReaderCloser(lg, dbsnap)
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// put the []byte snapshot of store into raft snapshot and return the merged snapshot with
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// KV readCloser snapshot.
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snapshot := raftpb.Snapshot{
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Metadata: raftpb.SnapshotMetadata{
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Index: snapi,
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Term: snapt,
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ConfState: confState,
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},
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Data: d,
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}
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m.Snapshot = &snapshot
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verifySnapshotIndex(snapshot, s.consistIndex.ConsistentIndex())
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return *snap.NewMessage(m, rc, dbsnap.Size())
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}
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func newSnapshotReaderCloser(lg *zap.Logger, snapshot backend.Snapshot) io.ReadCloser {
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pr, pw := io.Pipe()
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go func() {
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n, err := snapshot.WriteTo(pw)
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if err == nil {
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lg.Info(
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"sent database snapshot to writer",
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zap.Int64("bytes", n),
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zap.String("size", humanize.Bytes(uint64(n))),
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)
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} else {
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lg.Warn(
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"failed to send database snapshot to writer",
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zap.String("size", humanize.Bytes(uint64(n))),
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zap.Error(err),
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)
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}
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pw.CloseWithError(err)
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err = snapshot.Close()
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if err != nil {
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lg.Panic("failed to close database snapshot", zap.Error(err))
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}
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}()
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return pr
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}
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