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
15package wal
16
17import (
18	"fmt"
19	"os"
20	"path/filepath"
21
22	"github.com/coreos/etcd/pkg/fileutil"
23)
24
25// filePipeline pipelines allocating disk space
26type 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
39func 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.
53func (fp *filePipeline) Open() (f *fileutil.LockedFile, err error) {
54	select {
55	case f = <-fp.filec:
56	case err = <-fp.errc:
57	}
58	return
59}
60
61func (fp *filePipeline) Close() error {
62	close(fp.donec)
63	return <-fp.errc
64}
65
66func (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
81func (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}
98