file_pipeline.go

Documentation: go.etcd.io/etcd/server/v3/wal

     1  // 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  
    15  package wal
    16  
    17  import (
    18  	"fmt"
    19  	"os"
    20  	"path/filepath"
    21  
    22  	"go.etcd.io/etcd/client/pkg/v3/fileutil"
    23  
    24  	"go.uber.org/zap"
    25  )
    26  
    27  // filePipeline pipelines allocating disk space
    28  type filePipeline struct {
    29  	lg *zap.Logger
    30  
    31  	// dir to put files
    32  	dir string
    33  	// size of files to make, in bytes
    34  	size int64
    35  	// count number of files generated
    36  	count int
    37  
    38  	filec chan *fileutil.LockedFile
    39  	errc  chan error
    40  	donec chan struct{}
    41  }
    42  
    43  func newFilePipeline(lg *zap.Logger, dir string, fileSize int64) *filePipeline {
    44  	if lg == nil {
    45  		lg = zap.NewNop()
    46  	}
    47  	fp := &filePipeline{
    48  		lg:    lg,
    49  		dir:   dir,
    50  		size:  fileSize,
    51  		filec: make(chan *fileutil.LockedFile),
    52  		errc:  make(chan error, 1),
    53  		donec: make(chan struct{}),
    54  	}
    55  	go fp.run()
    56  	return fp
    57  }
    58  
    59  // Open returns a fresh file for writing. Rename the file before calling
    60  // Open again or there will be file collisions.
    61  func (fp *filePipeline) Open() (f *fileutil.LockedFile, err error) {
    62  	select {
    63  	case f = <-fp.filec:
    64  	case err = <-fp.errc:
    65  	}
    66  	return f, err
    67  }
    68  
    69  func (fp *filePipeline) Close() error {
    70  	close(fp.donec)
    71  	return <-fp.errc
    72  }
    73  
    74  func (fp *filePipeline) alloc() (f *fileutil.LockedFile, err error) {
    75  	// count % 2 so this file isn't the same as the one last published
    76  	fpath := filepath.Join(fp.dir, fmt.Sprintf("%d.tmp", fp.count%2))
    77  	if f, err = fileutil.LockFile(fpath, os.O_CREATE|os.O_WRONLY, fileutil.PrivateFileMode); err != nil {
    78  		return nil, err
    79  	}
    80  	if err = fileutil.Preallocate(f.File, fp.size, true); err != nil {
    81  		fp.lg.Error("failed to preallocate space when creating a new WAL", zap.Int64("size", fp.size), zap.Error(err))
    82  		f.Close()
    83  		return nil, err
    84  	}
    85  	fp.count++
    86  	return f, nil
    87  }
    88  
    89  func (fp *filePipeline) run() {
    90  	defer close(fp.errc)
    91  	for {
    92  		f, err := fp.alloc()
    93  		if err != nil {
    94  			fp.errc <- err
    95  			return
    96  		}
    97  		select {
    98  		case fp.filec <- f:
    99  		case <-fp.donec:
   100  			os.Remove(f.Name())
   101  			f.Close()
   102  			return
   103  		}
   104  	}
   105  }
   106
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