blob: 65075d281110cf445418640936d7c08d315512db [file] [log] [blame]
Matthias Andreas Benkard832a54e2019-01-29 09:27:38 +01001// Go support for leveled logs, analogous to https://code.google.com/p/google-glog/
2//
3// Copyright 2013 Google Inc. All Rights Reserved.
4//
5// Licensed under the Apache License, Version 2.0 (the "License");
6// you may not use this file except in compliance with the License.
7// You may obtain a copy of the License at
8//
9// http://www.apache.org/licenses/LICENSE-2.0
10//
11// Unless required by applicable law or agreed to in writing, software
12// distributed under the License is distributed on an "AS IS" BASIS,
13// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14// See the License for the specific language governing permissions and
15// limitations under the License.
16
17// File I/O for logs.
18
19package glog
20
21import (
22 "errors"
23 "flag"
24 "fmt"
25 "os"
26 "os/user"
27 "path/filepath"
28 "strings"
29 "sync"
30 "time"
31)
32
33// MaxSize is the maximum size of a log file in bytes.
34var MaxSize uint64 = 1024 * 1024 * 1800
35
36// logDirs lists the candidate directories for new log files.
37var logDirs []string
38
39// If non-empty, overrides the choice of directory in which to write logs.
40// See createLogDirs for the full list of possible destinations.
41var logDir = flag.String("log_dir", "", "If non-empty, write log files in this directory")
42
43func createLogDirs() {
44 if *logDir != "" {
45 logDirs = append(logDirs, *logDir)
46 }
47 logDirs = append(logDirs, os.TempDir())
48}
49
50var (
51 pid = os.Getpid()
52 program = filepath.Base(os.Args[0])
53 host = "unknownhost"
54 userName = "unknownuser"
55)
56
57func init() {
58 h, err := os.Hostname()
59 if err == nil {
60 host = shortHostname(h)
61 }
62
63 current, err := user.Current()
64 if err == nil {
65 userName = current.Username
66 }
67
68 // Sanitize userName since it may contain filepath separators on Windows.
69 userName = strings.Replace(userName, `\`, "_", -1)
70}
71
72// shortHostname returns its argument, truncating at the first period.
73// For instance, given "www.google.com" it returns "www".
74func shortHostname(hostname string) string {
75 if i := strings.Index(hostname, "."); i >= 0 {
76 return hostname[:i]
77 }
78 return hostname
79}
80
81// logName returns a new log file name containing tag, with start time t, and
82// the name for the symlink for tag.
83func logName(tag string, t time.Time) (name, link string) {
84 name = fmt.Sprintf("%s.%s.%s.log.%s.%04d%02d%02d-%02d%02d%02d.%d",
85 program,
86 host,
87 userName,
88 tag,
89 t.Year(),
90 t.Month(),
91 t.Day(),
92 t.Hour(),
93 t.Minute(),
94 t.Second(),
95 pid)
96 return name, program + "." + tag
97}
98
99var onceLogDirs sync.Once
100
101// create creates a new log file and returns the file and its filename, which
102// contains tag ("INFO", "FATAL", etc.) and t. If the file is created
103// successfully, create also attempts to update the symlink for that tag, ignoring
104// errors.
105func create(tag string, t time.Time) (f *os.File, filename string, err error) {
106 onceLogDirs.Do(createLogDirs)
107 if len(logDirs) == 0 {
108 return nil, "", errors.New("log: no log dirs")
109 }
110 name, link := logName(tag, t)
111 var lastErr error
112 for _, dir := range logDirs {
113 fname := filepath.Join(dir, name)
114 f, err := os.Create(fname)
115 if err == nil {
116 symlink := filepath.Join(dir, link)
117 os.Remove(symlink) // ignore err
118 os.Symlink(name, symlink) // ignore err
119 return f, fname, nil
120 }
121 lastErr = err
122 }
123 return nil, "", fmt.Errorf("log: cannot create log: %v", lastErr)
124}