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The Timbre Clojars group was recently changed. Please update your project.clj to use:

[com.taoensso/timbre "{VERSION}"]

Timbre, a (sane) logging library for Clojure

Logging with Java can be maddeningly, unnecessarily hard. Particularly if all you want is something simple that works out the box.

tools.logging helps, but it doesn't save you from the mess of logger dependencies and configuration hell.

Timbre is an attempt to make simple logging simple and more complex logging possible.

What's In The Box?

  • Small, uncomplicated all-Clojure library.
  • Super-simple map-based config: no arcane XML or properties files.
  • Decent performance (low overhead).
  • Flexible fn-centric appender model.
  • Sensible built-in appenders including simple email appender.
  • Tunable flood control.
  • Asynchronous logging support.

Status Build Status

Timbre was built in a day after I finally lost my patience trying to configure Log4j. I tried to keep the design simple and sensible but I didn't spend much time thinking about it so there may still be room for improvement. In particular the configuration and appender formats are still subject to change.

Getting Started


Depend on Timbre in your project.clj:

[com.taoensso/timbre "0.5.1"]

and require the library:

(ns my-app
  (:use [timbre.core :as timbre :only (trace debug info warn error fatal spy)])

Start Logging

By default, Timbre gives you basic print output to *out*/*err* at a debug logging level:

(info "This will print")
=> 2012-May-28 17:26:11:444 +0700 INFO [timbre.tests] - This will print

(trace "This won't print due to insufficient logging level")
=> nil

There's little overhead for checking logging levels:

(time (trace (Thread/sleep 5000)))
=> "Elapsed time: 0.054 msecs"

(time (when true))
=> "Elapsed time: 0.051 msecs"

First-argument exceptions generate a stack trace:

(info (Exception. "Oh noes") "arg1" "arg2")
=> 2012-May-28 17:35:16:132 +0700 INFO [timbre.tests] - arg1 arg2
java.lang.Exception: Oh noes
            NO_SOURCE_FILE:1 timbre.tests/eval6409


Easily adjust the current logging level:

(timbre/set-level! :warn)

And the default timestamp formatting for log messages:

(timbre/set-config! [:shared-appender-config :timestamp-pattern]
                    "yyyy-MMM-dd HH:mm:ss ZZ")
(timbre/set-config! [:shared-appender-config :locale]

Enable the standard Postal-based email appender:

(timbre/set-config! [:shared-appender-config :postal]
                    ^{:host "" :user "jsmith" :pass "sekrat!!1"}
                    {:from "" :to ""})

(timbre/set-config! [:appenders :postal :enabled?] true)

Rate-limit to one email per message per minute:

(timbre/set-config! [:appenders :postal :max-message-per-msecs] 60000)

And make sure emails are sent asynchronously:

(timbre/set-config! [:appenders :postal :async?] true)

Custom Appenders

Writing a custom appender is easy:

 [:appenders :my-appender]
 {:doc       "Hello-world appender"
  :min-level :debug
  :enabled?  true
  :async?    false
  :max-message-per-msecs nil ; No rate limiting
  :fn (fn [{:keys [ap-config level error? instant timestamp
                  ns message more] :as args}]
        (when-not (:production-mode? ap-config)
          (apply println timestamp "Hello world!" message more)))

And because appender fns are just regular Clojure fns, you have unlimited power: write to your database, send a message over the network, check some other state (e.g. environment config) before making a choice, etc.

See (doc timbre/config) for more information on appenders.

Timbre Supports the ClojureWerkz Project Goals

ClojureWerkz is a growing collection of open-source, batteries-included Clojure libraries that emphasise modern targets, great documentation, and thorough testing.

Contact & Contribution

Reach me (Peter Taoussanis) at ptaoussanis at for questions/comments/suggestions/whatever. I'm very open to ideas if you have any!

I'm also on Twitter: @ptaoussanis.


Copyright © 2012 Peter Taoussanis

Distributed under the Eclipse Public License, the same as Clojure.

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