go.etcd.io/etcd@v3.3.27+incompatible/wal/file_pipeline.go (about)

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