rollinglog

Package provides a simple rolling logger

Inspired by lumberjack (https://github.com/natefinch/lumberjack)

Rollinglog is intended to be one part of a logging infrastructure. 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 to which logs are written.

Rollinglog plays well with any logging package that can write to an io.Writer, including the standard library's log package.

Install

go get github.com/PSyton/rollinglog

Usage

One can use rollinglog with the standard library's log package, just pass it into the SetOutput function when your application starts.

import "github.com/PSyton/rollinglog"

// Create logger writes log into file.log in current folder and limits maximum size by 10Mb
// No limits for backups and no compresion enabled
logger := rollinglog.New(rollinglog.LogFile("file.log"), rollinglog.MaxBytes(10 * 1024 * 1024))

log.SetOutput(logger)

...
// Close the logger
logger.Close()

Details

Logger is an io.WriteCloser that writes to the specified file.

Logger opens or creates the logfile on first Write. If the file exists and is less than MaxBytes bytes, rollinglog will open and append to that file. If the file exists and its size is larger MaxBytes, 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.

Whenever a write would cause the current log file exceed MaxBytes bytes, the current file is closed, renamed, and a new log file created with the original name. Thus, the filename you give Logger is always the "current" log file.

Backups use the log file name given to Logger, in the form name.timestamp.ext where name is the filename without the extension, timestamp is the time at which the log was rotated formatted with the time.Time format of TimeFormat and the extension is the original extension. For example, if your LogFile is /var/log/foo/server.log, a backup created at 6:30pm on Nov 11 2016 would use the filename /var/log/foo/server.20161104183000.000.log

Cleaning Up Old Log Files

Whenever a new logfile gets created, old log files may be deleted. The most recent files according to the encoded timestamp will be retained, up to a number equal to MaxBackups (or all of them if MaxBackups is 0). Any files with an encoded timestamp older than MaxAge days are deleted, regardless of MaxBackups. Note that the time encoded in the timestamp is the rotation 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.

Options

rollinglog.New accepts functional options:

• rollinglog.WithLogFile(aFilnename string) - sets log file name with path. By default logger use file name os.Args[0]-rollinglog.log and place it in os.TempDir()
• rollinglog.WithMaxBytes(aSize uint64) - limits log size in bytes. When limit exceeded log will be rotated. (Defailt: 0 - never rotate)
• rollinglog.WithMaxBackups(aCount int) - sets the max count of backups to store (Default: 0 - no limit)
• rollinglog.WithMaxAge(aDays int) - sets the number of days to store backups (Default: 0 - no limit)
• rollinglog.UseCompression - allows to enable compression for backups (disabled by default)
• rollinglog.UseLocaltime - allows use local time for timestamps instead default UTC
• rollinglog.WithErrorHandler(eh ErrHandler) - allows to set error handler for logger.