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update readme and mention gopkg.in in godoc

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Nate Finch
2014-06-27 06:13:39 -04:00
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# lumberjack [![GoDoc](https://godoc.org/github.com/natefinch/lumberjack?status.png)](https://godoc.org/github.com/natefinch/lumberjack) [![Build Status](https://travis-ci.org/natefinch/lumberjack.png)](https://travis-ci.org/natefinch/lumberjack) # lumberjack [![GoDoc](https://godoc.org/github.com/natefinch/lumberjack?status.png)](https://godoc.org/github.com/natefinch/lumberjack) [![Build Status](https://travis-ci.org/natefinch/lumberjack.png)](https://travis-ci.org/natefinch/lumberjack)
### Lumberjack is a Go package for writing logs to rolling files. ### Lumberjack is a Go package for writing logs to rolling files.
Package lumberjack provides a rolling logger.
Note that this is v2.0 of lumberjack, and should be imported using gopkg.in
thusly:
import "gopkg.in/natefinch/lumberjack.v2"
The package name remains simply lumberjack, and the code resides at
https://github.com/natefinch/lumberjack under the v2.0 branch.
Lumberjack is intended to be one part of a logging infrastructure. Lumberjack is intended to be one part of a logging infrastructure.
It is not an all-in-one solution, but instead is a pluggable It is not an all-in-one solution, but instead is a pluggable
component at the bottom of the logging stack that simply controls the files component at the bottom of the logging stack that simply controls the files
to which logs are written. to which logs are written.
Lumberjack plays well with any logger that can write to an io.Writer, Lumberjack plays well with any logging package that can write to an
including the standard library's log package. io.Writer, including the standard library's log package.
Lumberjack assumes that only one process is writing to the output files. Lumberjack assumes that only one process is writing to the output files.
Using the same lumberjack configuration from multiple processes on the same Using the same lumberjack configuration from multiple processes on the same
machine will result in improper behavior. machine will result in improper behavior.
#### Example
To use lumberjack with the standard library's log package, just pass it into the **Example**
SetOutput function when your application starts.
To use lumberjack with the standard library's log package, just pass it into the SetOutput function when your application starts.
Code: Code:
```go ```go
log.SetOutput(&lumberjack.Logger{ log.SetOutput(&lumberjack.Logger{
Dir: "/var/log/myapp/", Filename: "/var/log/myapp/foo.log",
NameFormat: "2006-01-02T15-04-05.000.log", MaxSize: 500, // megabytes
MaxSize: lumberjack.Gigabyte,
MaxBackups: 3, MaxBackups: 3,
MaxAge: 28, MaxAge: 28,
}) })
@@ -34,35 +42,23 @@ log.SetOutput(&lumberjack.Logger{
## Constants
``` go
const (
Megabyte = 1024 * 1024
Gigabyte = 1024 * Megabyte
)
```
## type Logger ## type Logger
``` go ``` go
type Logger struct { type Logger struct {
// Dir determines the directory in which to store log files. // Filename is the file to write logs to. Backup log files will be retained
// It defaults to os.TempDir() if empty. // in the same directory. It uses <processname>-lumberjack.log in
Dir string `json:"dir" yaml:"dir"` // os.TempDir() if empty.
Filename string `json:"filename" yaml:"filename"`
// NameFormat is the time formatting layout used to generate filenames. // MaxSize is the maximum size in megabytes of the log file before it gets
// It defaults to "2006-01-02T15-04-05.000.log". // rotated. It defaults to 100 megabytes.
NameFormat string `json:"nameformat" yaml:"nameformat"` MaxSize int `json:"maxsize" yaml:"maxsize"`
// MaxSize is the maximum size in bytes of the log file before it gets // MaxAge is the maximum number of days to retain old log files based on the
// rolled. It defaults to 100 megabytes. // timestamp encoded in their filename. Note that a day is defined as 24
MaxSize int64 `json:"maxsize" yaml:"maxsize"` // hours and may not exactly correspond to calendar days due to daylight
// savings, leap seconds, etc. The default is not to remove old log files
// MaxAge is the maximum number of days to retain old log files based on // based on age.
// FileInfo.ModTime. Note that a day is defined as 24 hours and may not
// exactly correspond to calendar days due to daylight savings, leap
// seconds, etc. The default is not to remove old log files based on age.
MaxAge int `json:"maxage" yaml:"maxage"` MaxAge int `json:"maxage" yaml:"maxage"`
// MaxBackups is the maximum number of old log files to retain. The default // MaxBackups is the maximum number of old log files to retain. The default
@@ -70,36 +66,34 @@ type Logger struct {
// deleted.) // deleted.)
MaxBackups int `json:"maxbackups" yaml:"maxbackups"` MaxBackups int `json:"maxbackups" yaml:"maxbackups"`
// LocalTime determines if the time used for formatting the filename is the // LocalTime determines if the time used for formatting the timestamps in
// computer's local time. The default is to use UTC time. // backup files is the computer's local time. The default is to use UTC
// time.
LocalTime bool `json:"localtime" yaml:"localtime"` LocalTime bool `json:"localtime" yaml:"localtime"`
// contains filtered or unexported fields // contains filtered or unexported fields
} }
``` ```
Logger is an io.WriteCloser that writes to a log file in the given directory Logger is an io.WriteCloser that writes to the specified filename.
with the given NameFormat. NameFormat should include a time formatting
layout in it that produces a valid unique filename for the OS. For more
about time formatting layouts, read a http://golang.org/pkg/time/#pkg-constants.
The date encoded in the filename by NameFormat is used to determine which log Logger opens or creates the logfile on first Write. If the file exists and
files are most recent in several situations. is less than MaxSize megabytes, lumberjack will open and append to that file.
If the file exists and its size is >= MaxSize megabytes, the file is renamed
by putting the current time in a timestamp in the name immediately before the
file's extension (or the end of the filename if there's no extension). A new
log file is then created using original filename.
Logger opens or creates a logfile on first Write. It looks for files in the Whenever a write would cause the current log file exceed MaxSize megabytes,
directory that match its name format, and if the one with the most recent the current file is closed, renamed, and a new log file created with the
NameFormat date is less than MaxSize, it will open and append to that file. original name. Thus, the filename you give Logger is always the "current" log
If no such file exists, or the file is >= MaxSize, a new file is created file.
using the current time with NameFormat to generate the filename.
Whenever a write would cause the current log file exceed MaxSize, a new file
is created using the current time.
### Cleaning Up Old Log Files ### Cleaning Up Old Log Files
Whenever a new file gets created, old log files may be deleted. The log file Whenever a new logfile gets created, old log files may be deleted. The most
directory is scanned for files that match NameFormat. The most recent files recent files according to the encoded timestamp will be retained, up to a
according to their NameFormat date will be retained, up to a number equal to number equal to MaxBackups (or all of them if MaxBackups is 0). Any files
MaxBackups (or all of them if MaxBackups is 0). Any files with a last with an encoded timestamp older than MaxAge days are deleted, regardless of
modified time (based on FileInfo.ModTime) older than MaxAge days are deleted, MaxBackups. Note that the time encoded in the timestamp is the rotation
regardless of MaxBackups. time, which may differ from the last time that file was written to.
If MaxBackups and MaxAge are both 0, no old log files will be deleted. If MaxBackups and MaxAge are both 0, no old log files will be deleted.
@@ -131,12 +125,12 @@ rotations outside of the normal rotation rules, such as in response to
SIGHUP. After rotating, this initiates a cleanup of old log files according SIGHUP. After rotating, this initiates a cleanup of old log files according
to the normal rules. to the normal rules.
**Example**
#### Example
Example of how to rotate in response to SIGHUP. Example of how to rotate in response to SIGHUP.
Code: Code:
```go ```go
l := &lumberjack.Logger{} l := &lumberjack.Logger{}
log.SetOutput(l) log.SetOutput(l)
@@ -151,15 +145,14 @@ Code:
}() }()
``` ```
### func (\*Logger) Write ### func (\*Logger) Write
``` go ``` go
func (l *Logger) Write(p []byte) (n int, err error) func (l *Logger) Write(p []byte) (n int, err error)
``` ```
Write implements io.Writer. If a write would cause the log file to be larger Write implements io.Writer. If a write would cause the log file to be larger
than MaxSize, a new log file is created using the current time formatted with than MaxSize, the file is closed, renamed to include a timestamp of the
PathFormat. If the length of the write is greater than MaxSize, an error is current time, and a new log file is created using the original log file name.
returned. If the length of the write is greater than MaxSize, an error is returned.
lumberjack.go
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// Package lumberjack provides a rolling logger. // Package lumberjack provides a rolling logger.
// //
// Note that this is v2.0 of lumberjack, and should be imported using gopkg.in
// thusly:
//
// import "gopkg.in/natefinch/lumberjack.v2"
//
// The package name remains simply lumberjack, and the code resides at
// https://github.com/natefinch/lumberjack under the v2.0 branch.
//
// Lumberjack is intended to be one part of a logging infrastructure. // Lumberjack is intended to be one part of a logging infrastructure.
// It is not an all-in-one solution, but instead is a pluggable // It is not an all-in-one solution, but instead is a pluggable
// component at the bottom of the logging stack that simply controls the files // component at the bottom of the logging stack that simply controls the files