mirror of
https://github.com/etcd-io/etcd.git
synced 2024-09-27 06:25:44 +00:00
134 lines
3.1 KiB
Go
134 lines
3.1 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 wal
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import (
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"encoding/binary"
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"hash"
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"io"
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"os"
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"sync"
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"time"
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"go.etcd.io/etcd/pkg/v3/crc"
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"go.etcd.io/etcd/pkg/v3/ioutil"
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"go.etcd.io/etcd/server/v3/storage/wal/walpb"
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)
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// walPageBytes is the alignment for flushing records to the backing Writer.
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// It should be a multiple of the minimum sector size so that WAL can safely
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// distinguish between torn writes and ordinary data corruption.
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const walPageBytes = 8 * minSectorSize
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type encoder struct {
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mu sync.Mutex
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bw *ioutil.PageWriter
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crc hash.Hash32
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buf []byte
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uint64buf []byte
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}
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func newEncoder(w io.Writer, prevCrc uint32, pageOffset int) *encoder {
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return &encoder{
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bw: ioutil.NewPageWriter(w, walPageBytes, pageOffset),
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crc: crc.New(prevCrc, crcTable),
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// 1MB buffer
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buf: make([]byte, 1024*1024),
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uint64buf: make([]byte, 8),
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}
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}
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// newFileEncoder creates a new encoder with current file offset for the page writer.
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func newFileEncoder(f *os.File, prevCrc uint32) (*encoder, error) {
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offset, err := f.Seek(0, io.SeekCurrent)
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if err != nil {
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return nil, err
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}
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return newEncoder(f, prevCrc, int(offset)), nil
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}
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func (e *encoder) encode(rec *walpb.Record) error {
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e.mu.Lock()
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defer e.mu.Unlock()
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e.crc.Write(rec.Data)
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rec.Crc = e.crc.Sum32()
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var (
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data []byte
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err error
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n int
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)
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if rec.Size() > len(e.buf) {
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data, err = rec.Marshal()
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if err != nil {
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return err
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}
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} else {
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n, err = rec.MarshalTo(e.buf)
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if err != nil {
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return err
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}
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data = e.buf[:n]
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}
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data, lenField := prepareDataWithPadding(data)
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return write(e.bw, e.uint64buf, data, lenField)
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}
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func encodeFrameSize(dataBytes int) (lenField uint64, padBytes int) {
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lenField = uint64(dataBytes)
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// force 8 byte alignment so length never gets a torn write
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padBytes = (8 - (dataBytes % 8)) % 8
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if padBytes != 0 {
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lenField |= uint64(0x80|padBytes) << 56
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}
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return lenField, padBytes
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}
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func (e *encoder) flush() error {
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e.mu.Lock()
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defer e.mu.Unlock()
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return e.bw.Flush()
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}
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func prepareDataWithPadding(data []byte) ([]byte, uint64) {
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lenField, padBytes := encodeFrameSize(len(data))
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if padBytes != 0 {
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data = append(data, make([]byte, padBytes)...)
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}
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return data, lenField
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}
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func write(w io.Writer, uint64buf, data []byte, lenField uint64) error {
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// write padding info
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binary.LittleEndian.PutUint64(uint64buf, lenField)
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start := time.Now()
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nv, err := w.Write(uint64buf)
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walWriteBytes.Add(float64(nv))
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if err != nil {
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return err
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}
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// write the record with padding
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n, err := w.Write(data)
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walWriteSec.Observe(time.Since(start).Seconds())
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walWriteBytes.Add(float64(n))
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return err
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}
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