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file_pipeline.go
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/
file_pipeline.go
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// Copyright 2016 The etcd Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package wal
import (
"fmt"
"os"
"path/filepath"
"github.com/coreos/etcd/pkg/fileutil"
)
// filePipeline pipelines allocating disk space
type filePipeline struct {
// dir to put files
dir string
// size of files to make, in bytes
size int64
// count number of files generated
count int
filec chan *fileutil.LockedFile
errc chan error
donec chan struct{}
}
func newFilePipeline(dir string, fileSize int64) *filePipeline {
fp := &filePipeline{
dir: dir,
size: fileSize,
filec: make(chan *fileutil.LockedFile),
errc: make(chan error, 1),
donec: make(chan struct{}),
}
go fp.run()
return fp
}
// Open returns a fresh file for writing. Rename the file before calling
// Open again or there will be file collisions.
func (fp *filePipeline) Open() (f *fileutil.LockedFile, err error) {
select {
case f = <-fp.filec:
case err = <-fp.errc:
}
return f, err
}
func (fp *filePipeline) Close() error {
close(fp.donec)
return <-fp.errc
}
func (fp *filePipeline) alloc() (f *fileutil.LockedFile, err error) {
// count % 2 so this file isn't the same as the one last published
fpath := filepath.Join(fp.dir, fmt.Sprintf("%d.tmp", fp.count%2))
if f, err = fileutil.LockFile(fpath, os.O_CREATE|os.O_WRONLY, fileutil.PrivateFileMode); err != nil {
return nil, err
}
if err = fileutil.Preallocate(f.File, fp.size, true); err != nil {
plog.Errorf("failed to allocate space when creating new wal file (%v)", err)
f.Close()
return nil, err
}
fp.count++
return f, nil
}
func (fp *filePipeline) run() {
defer close(fp.errc)
for {
f, err := fp.alloc()
if err != nil {
fp.errc <- err
return
}
select {
case fp.filec <- f:
case <-fp.donec:
os.Remove(f.Name())
f.Close()
return
}
}
}