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180 lines
6.2 KiB
Markdown
180 lines
6.2 KiB
Markdown
# 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)
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### Lumberjack is a Go package for writing logs to rolling files.
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Package lumberjack provides a rolling logger.
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Note that this is v2.0 of lumberjack, and should be imported using gopkg.in
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thusly:
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import "gopkg.in/natefinch/lumberjack.v2"
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The package name remains simply lumberjack, and the code resides at
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https://github.com/natefinch/lumberjack under the v2.0 branch.
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Lumberjack is intended to be one part of a logging infrastructure.
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It is not an all-in-one solution, but instead is a pluggable
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component at the bottom of the logging stack that simply controls the files
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to which logs are written.
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Lumberjack plays well with any logging package that can write to an
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io.Writer, including the standard library's log package.
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Lumberjack assumes that only one process is writing to the output files.
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Using the same lumberjack configuration from multiple processes on the same
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machine will result in improper behavior.
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**Example**
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To use lumberjack with the standard library's log package, just pass it into the SetOutput function when your application starts.
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Code:
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```go
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log.SetOutput(&lumberjack.Logger{
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Filename: "/var/log/myapp/foo.log",
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MaxSize: 500, // megabytes
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MaxBackups: 3,
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MaxAge: 28, //days
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Compress: true, // disabled by default
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})
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```
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## type Logger
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``` go
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type Logger struct {
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// Filename is the file to write logs to. Backup log files will be retained
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// in the same directory. It uses <processname>-lumberjack.log in
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// os.TempDir() if empty.
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Filename string `json:"filename" yaml:"filename"`
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// MaxSize is the maximum size in megabytes of the log file before it gets
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// rotated. It defaults to 100 megabytes.
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MaxSize int `json:"maxsize" yaml:"maxsize"`
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// MaxAge is the maximum number of days to retain old log files based on the
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// timestamp encoded in their filename. Note that a day is defined as 24
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// hours and may not exactly correspond to calendar days due to daylight
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// savings, leap seconds, etc. The default is not to remove old log files
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// based on age.
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MaxAge int `json:"maxage" yaml:"maxage"`
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// MaxBackups is the maximum number of old log files to retain. The default
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// is to retain all old log files (though MaxAge may still cause them to get
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// deleted.)
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MaxBackups int `json:"maxbackups" yaml:"maxbackups"`
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// LocalTime determines if the time used for formatting the timestamps in
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// backup files is the computer's local time. The default is to use UTC
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// time.
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LocalTime bool `json:"localtime" yaml:"localtime"`
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// Compress determines if the rotated log files should be compressed
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// using gzip. The default is not to perform compression.
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Compress bool `json:"compress" yaml:"compress"`
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// contains filtered or unexported fields
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}
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```
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Logger is an io.WriteCloser that writes to the specified filename.
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Logger opens or creates the logfile on first Write. If the file exists and
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is less than MaxSize megabytes, lumberjack will open and append to that file.
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If the file exists and its size is >= MaxSize megabytes, the file is renamed
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by putting the current time in a timestamp in the name immediately before the
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file's extension (or the end of the filename if there's no extension). A new
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log file is then created using original filename.
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Whenever a write would cause the current log file exceed MaxSize megabytes,
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the current file is closed, renamed, and a new log file created with the
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original name. Thus, the filename you give Logger is always the "current" log
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file.
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Backups use the log file name given to Logger, in the form `name-timestamp.ext`
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where name is the filename without the extension, timestamp is the time at which
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the log was rotated formatted with the time.Time format of
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`2006-01-02T15-04-05.000` and the extension is the original extension. For
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example, if your Logger.Filename is `/var/log/foo/server.log`, a backup created
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at 6:30pm on Nov 11 2016 would use the filename
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`/var/log/foo/server-2016-11-04T18-30-00.000.log`
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### Cleaning Up Old Log Files
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Whenever a new logfile gets created, old log files may be deleted. The most
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recent files according to the encoded timestamp will be retained, up to a
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number equal to MaxBackups (or all of them if MaxBackups is 0). Any files
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with an encoded timestamp older than MaxAge days are deleted, regardless of
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MaxBackups. Note that the time encoded in the timestamp is the rotation
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time, which may differ from the last time that file was written to.
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If MaxBackups and MaxAge are both 0, no old log files will be deleted.
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### func (\*Logger) Close
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``` go
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func (l *Logger) Close() error
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```
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Close implements io.Closer, and closes the current logfile.
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### func (\*Logger) Rotate
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``` go
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func (l *Logger) Rotate() error
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```
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Rotate causes Logger to close the existing log file and immediately create a
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new one. This is a helper function for applications that want to initiate
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rotations outside of the normal rotation rules, such as in response to
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SIGHUP. After rotating, this initiates a cleanup of old log files according
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to the normal rules.
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**Example**
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Example of how to rotate in response to SIGHUP.
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Code:
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```go
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l := &lumberjack.Logger{}
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log.SetOutput(l)
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c := make(chan os.Signal, 1)
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signal.Notify(c, syscall.SIGHUP)
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go func() {
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for {
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<-c
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l.Rotate()
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}
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}()
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```
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### func (\*Logger) Write
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``` go
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func (l *Logger) Write(p []byte) (n int, err error)
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```
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Write implements io.Writer. If a write would cause the log file to be larger
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than MaxSize, the file is closed, renamed to include a timestamp of the
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current time, and a new log file is created using the original log file name.
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If the length of the write is greater than MaxSize, an error is returned.
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- - -
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Generated by [godoc2md](http://godoc.org/github.com/davecheney/godoc2md)
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