github.com/v2pro/plz@v0.0.0-20221028024117-e5f9aec5b631/countlog/output/lumberjack/README.md (about) 1 # lumberjack [](https://godoc.org/gopkg.in/natefinch/lumberjack.v2) [](https://travis-ci.org/natefinch/lumberjack) [](https://ci.appveyor.com/project/natefinch/lumberjack) [](https://coveralls.io/r/natefinch/lumberjack?branch=v2.0) 2 3 ### Lumberjack is a Go package for writing logs to rolling files. 4 5 Package lumberjack provides a rolling logger. 6 7 Note that this is v2.0 of lumberjack, and should be imported using gopkg.in 8 thusly: 9 10 import "gopkg.in/natefinch/lumberjack.v2" 11 12 The package name remains simply lumberjack, and the code resides at 13 https://github.com/natefinch/lumberjack under the v2.0 branch. 14 15 Lumberjack is intended to be one part of a logging infrastructure. 16 It is not an all-in-one solution, but instead is a pluggable 17 component at the bottom of the logging stack that simply controls the files 18 to which logs are written. 19 20 Lumberjack plays well with any logging package that can write to an 21 io.Writer, including the standard library's log package. 22 23 Lumberjack assumes that only one process is writing to the output files. 24 Using the same lumberjack configuration from multiple processes on the same 25 machine will result in improper behavior. 26 27 28 **Example** 29 30 To use lumberjack with the standard library's log package, just pass it into the SetOutput function when your application starts. 31 32 Code: 33 34 ```go 35 log.SetOutput(&lumberjack.Logger{ 36 Filename: "/var/log/myapp/foo.log", 37 MaxSize: 500, // megabytes 38 MaxBackups: 3, 39 MaxAge: 28, //days 40 Compress: true, // disabled by default 41 }) 42 ``` 43 44 45 46 ## type Logger 47 ``` go 48 type Logger struct { 49 // Filename is the file to write logs to. Backup log files will be retained 50 // in the same directory. It uses <processname>-lumberjack.log in 51 // os.TempDir() if empty. 52 Filename string `json:"filename" yaml:"filename"` 53 54 // MaxSize is the maximum size in megabytes of the log file before it gets 55 // rotated. It defaults to 100 megabytes. 56 MaxSize int `json:"maxsize" yaml:"maxsize"` 57 58 // MaxAge is the maximum number of days to retain old log files based on the 59 // timestamp encoded in their filename. Note that a day is defined as 24 60 // hours and may not exactly correspond to calendar days due to daylight 61 // savings, leap seconds, etc. The default is not to remove old log files 62 // based on age. 63 MaxAge int `json:"maxage" yaml:"maxage"` 64 65 // MaxBackups is the maximum number of old log files to retain. The default 66 // is to retain all old log files (though MaxAge may still cause them to get 67 // deleted.) 68 MaxBackups int `json:"maxbackups" yaml:"maxbackups"` 69 70 // LocalTime determines if the time used for formatting the timestamps in 71 // backup files is the computer's local time. The default is to use UTC 72 // time. 73 LocalTime bool `json:"localtime" yaml:"localtime"` 74 75 // Compress determines if the rotated log files should be compressed 76 // using gzip. The default is not to perform compression. 77 Compress bool `json:"compress" yaml:"compress"` 78 // contains filtered or unexported fields 79 } 80 ``` 81 Logger is an io.WriteCloser that writes to the specified filename. 82 83 Logger opens or creates the logfile on first Write. If the file exists and 84 is less than MaxSize megabytes, lumberjack will open and append to that file. 85 If the file exists and its size is >= MaxSize megabytes, the file is renamed 86 by putting the current time in a timestamp in the name immediately before the 87 file's extension (or the end of the filename if there's no extension). A new 88 log file is then created using original filename. 89 90 Whenever a write would cause the current log file exceed MaxSize megabytes, 91 the current file is closed, renamed, and a new log file created with the 92 original name. Thus, the filename you give Logger is always the "current" log 93 file. 94 95 Backups use the log file name given to Logger, in the form `name-timestamp.ext` 96 where name is the filename without the extension, timestamp is the time at which 97 the log was rotated formatted with the time.Time format of 98 `2006-01-02T15-04-05.000` and the extension is the original extension. For 99 example, if your Logger.Filename is `/var/log/foo/server.log`, a backup created 100 at 6:30pm on Nov 11 2016 would use the filename 101 `/var/log/foo/server-2016-11-04T18-30-00.000.log` 102 103 ### Cleaning Up Old Log Files 104 Whenever a new logfile gets created, old log files may be deleted. The most 105 recent files according to the encoded timestamp will be retained, up to a 106 number equal to MaxBackups (or all of them if MaxBackups is 0). Any files 107 with an encoded timestamp older than MaxAge days are deleted, regardless of 108 MaxBackups. Note that the time encoded in the timestamp is the rotation 109 time, which may differ from the last time that file was written to. 110 111 If MaxBackups and MaxAge are both 0, no old log files will be deleted. 112 113 114 115 116 117 118 119 120 121 122 123 ### func (\*Logger) Close 124 ``` go 125 func (l *Logger) Close() error 126 ``` 127 Close implements io.Closer, and closes the current logfile. 128 129 130 131 ### func (\*Logger) Rotate 132 ``` go 133 func (l *Logger) Rotate() error 134 ``` 135 Rotate causes Logger to close the existing log file and immediately create a 136 new one. This is a helper function for applications that want to initiate 137 rotations outside of the normal rotation rules, such as in response to 138 SIGHUP. After rotating, this initiates a cleanup of old log files according 139 to the normal rules. 140 141 **Example** 142 143 Example of how to rotate in response to SIGHUP. 144 145 Code: 146 147 ```go 148 l := &lumberjack.Logger{} 149 log.SetOutput(l) 150 c := make(chan os.Signal, 1) 151 signal.Notify(c, syscall.SIGHUP) 152 153 go func() { 154 for { 155 <-c 156 l.Rotate() 157 } 158 }() 159 ``` 160 161 ### func (\*Logger) Write 162 ``` go 163 func (l *Logger) Write(p []byte) (n int, err error) 164 ``` 165 Write implements io.Writer. If a write would cause the log file to be larger 166 than MaxSize, the file is closed, renamed to include a timestamp of the 167 current time, and a new log file is created using the original log file name. 168 If the length of the write is greater than MaxSize, an error is returned. 169 170 171 172 173 174 175 176 177 178 - - - 179 Generated by [godoc2md](http://godoc.org/github.com/davecheney/godoc2md)