Configurable Logger for Go



This is a logger implementation that supports multiple log levels, multiple output destinations with configurable formats and levels for each. It also supports granular output configuration to get more detailed logging for specific files/packages. Timber includes support for standard XML or JSON config files to get you started quickly. It's also easy to configure in code if you want to DIY.


  • Log levels: Finest, Fine, Debug, Trace, Info, Warn, Error, Critical
  • External configuration via XML and JSON
  • Multiple log destinations (console, file, socket)
  • Configurable format per destination
  • Extensible and pluggable design (if you configure via code rather than XML)


I like the log4go design with multiple configurable loggers, but it did not support adding formatters to all of the loggers (it is only supported for files). I thought about trying to contribute patches to log4go but some of the features I wanted would break complete backwards compatibility so I decided to do a rewrite from scratch.

I try to expose everything possible that I think might be useful for someone to replace or extend.


The easiest way to use Timber is to use configure the built-in singleton:

import (
	log "timber"

func main() {
	// load xml config, json also supported

An example timber.xml and timber.json are included in the package. Timber does implement the interface of the go log package so replacing the log with Timber will work ok.

log.Close() should be called before your program exits to make sure all the buffers are drained and all messages are printed.


Logger is the interface that is used for logging itself with methods like Warn, Critical, Error, etc. All of these functions expect a Printf-like arguments and syntax for the message.

LogFormatter is a generic interface for taking a LogRecord and formatting into a string to be logged. PatFormatter is the only included implementation of this interface.

LogWriter interface wraps an underlying Writer but doesn't allow errors to propagate. There are implementations for writing to files, sockets and the console.

Timber is a MultiLogger which just means that it implements the Logger interface but can log messages to multiple destinations. Each destination has a LogWriter, level and LogFormatter.

Global is the default unconfigured instance of Timber which may be configured and used or, less commonly, replaced with your own instance (be sure to call Global.Close() before replacing for proper cleanup).

Are you planning to wrap Timber in your own logger? Ever notice that if you wrap the go log package or log4go the source file that gets printed is always your wrapper? Timber.FileDepth sets how far up the stack to go to find the file you actually want. It's set to DefaultFileDepth so add your wrapper stack depth to that.


  • Some of the runtime configuration changes have not been implemented, such as MultiLogger.SetLevel and MultiLogger.SetFormatter which change the Level or LogFormatter on-the-fly. Loggers may be added at any time with AddLogger but there is no way to delete loggers right now.


  • I don't support the log4go special handling of the first parameter and probably never will. Right now, all of the Logger methods just expect a Printf-like syntax. If there is demand, I may get the proc syntax in for delayed evaluation.
  • PatFormatter format codes are not the same as log4go
  • PatFormatter always adds a newline at the end of the string so if there's already one there, then you'll get 2 so using Timber to replace the go log package may look a bit messy depending on how you formatted your logging.
  • Embedded config sections

    Embedded config sections

    I'd rather not have to have a separate config file for my logs from the rest of my service. If we cleaned up and published the config structures (and a couple methods), it would make it trivial to embed timber config in a different config file...

    opened by dgrijalva 5
  • Different log levels depending on caller

    Different log levels depending on caller

    Like log4j, it would be nice to be able to configure different log levels for different parts of a program. In a large complicated program, it's sometimes necessary to enable debug logging for only one subsystem without spamming the logs with debug messages from every other subsystem. For example, in a webapp you might only want to enable debug logging for the code that validates incoming requests, without enabling any other debug output.

    This is different than the ability to configure a log level for each output, which doesn't fulfill the need I'm thinking of.

    This ability is similar to log4j's ability to configure different "loggers" for different classes/packages: , search for "logger". We could do something similar based on the filename returned from runtime.Caller(), such as determining the log level based on a prefix of the filename.

    opened by drevell 4
  • Add JSON support for configuration

    Add JSON support for configuration

    Added JSON support for configuration and included a example configuration file for it.

    Added a LoadJSONConfiguration and LoadXMLConfiguration function so that you can specifically load a certain type of config file, otherwise use LoadConfiguration attempts to figure out the type by the given filenames extension.

    opened by larzconwell 2
  • Rework of BufferedWriter to be safer and more flexible

    Rework of BufferedWriter to be safer and more flexible

    Two issues I'm solving here:

    1. bufio.Writer isn't safe to be accessed from multiple goroutines at once.
    2. buffer flushing is based on buffer size. apps that log take forever to flush


    1. changed all operations on bufio.Writer to happen in a goroutine
    2. added an explicit Flush method
    opened by dgrijalva 2
  • don't try and build syslog formatter on platforms which lack log/syslog

    don't try and build syslog formatter on platforms which lack log/syslog

    timber fails to build on windows, due to log/syslog having a build restriction (!windows,!plan9):

    This adds the same restriction to the syslog formatter, fixing the windows build

    opened by jbert 1
  • syslog sucks

    syslog sucks

    The go1.1 format implementation that I copied prints all sorts of garbage in rsyslogd (ubuntu) because of the timestamp format. Same for mac os x. This new format works and I figured it out from snooping the output of the logger command on ubuntu but is totally fucking broken on mac os. At this point I'm done fucking with it unless someone asks for mac os syslog to work.

    It kinda matches the old RFC 3164 but the hostname field didn't work right (rsyslog would just put the hostname doubled).

    opened by smw1218 0
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