timbre/README.md

**[API docs](http://ptaoussanis.github.io/timbre/)** | **[CHANGELOG](https://github.com/ptaoussanis/timbre/blob/master/CHANGELOG.md)** | [contact & contributing](#contact--contributing) | [other Clojure libs](https://www.taoensso.com/clojure-libraries) | [Twitter](https://twitter.com/#!/ptaoussanis) | current [semantic](http://semver.org/) version:

```clojure
[com.taoensso/timbre "2.7.0"] ; See CHANGELOG for breaking changes since 1.x
```

# Timbre, a (sane) Clojure logging & profiling library

Logging with Java can be maddeningly, unnecessarily hard. Particularly if all you want is something *simple that works out-the-box*. Timbre is an attempt to make **simple logging simple** and more **complex logging reasonable**. No XML!

## What's in the box™?
 * Small, uncomplicated **all-Clojure** library.
 * **Super-simple map-based config**: no arcane XML or properties files!
 * **Low overhead** with dynamic logging level.
 * **No overhead** with compile-time logging level. (v2.6+)
 * Flexible **fn-centric appender model** with **middleware**.
 * Sensible built-in appenders including simple **email appender**.
 * Tunable **rate limit** and **asynchronous** logging support.
 * Robust **namespace filtering**.
 * **[tools.logging](https://github.com/clojure/tools.logging) support** (optional).
 * Dead-simple, logging-level-aware **logging profiler**.

## Getting started

### Dependencies

Add the necessary dependency to your [Leiningen](http://leiningen.org/) `project.clj` and `require` the library in your ns:

```clojure
[com.taoensso/timbre "2.7.0"] ; project.clj
(ns my-app (:require [taoensso.timbre :as timbre
                      :refer (trace debug info warn error fatal spy with-log-level)])) ; ns
```

### Logging

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

```clojure
(info "This will print")
=> nil
%> 2012-May-28 17:26:11:444 +0700 localhost INFO [my-app] - This will print

(spy :info (* 5 4 3 2 1))
=> 120
%> 2012-May-28 17:26:14:138 +0700 localhost INFO [my-app] - (* 5 4 3 2 1) 120

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

There's little overhead for checking logging levels:

```clojure
(time (trace (Thread/sleep 5000)))
%> "Elapsed time: 0.054 msecs"

(time (when false))
%> "Elapsed time: 0.051 msecs"
```

And _no_ overhead when using a compile-time logging level (set `TIMBRE_LOG_LEVEL` environment variable):

```clojure
(time (dotimes [_ 1000000000] (trace (Thread/sleep 5000))))
%> "Elapsed time: 387.159 msecs"

(time (dotimes [_ 1000000000] nil))
%> "Elapsed time: 389.231 msecs"
```

First-argument exceptions generate a stack trace:

```clojure
(info (Exception. "Oh noes") "arg1" "arg2")
%> 2012-May-28 17:35:16:132 +0700 localhost INFO [my-app] - arg1 arg2
java.lang.Exception: Oh noes
            NO_SOURCE_FILE:1 my-app/eval6409
          Compiler.java:6511 clojure.lang.Compiler.eval
          <...>
```

### Configuration

Configuring Timbre couldn't be simpler. Let's check out (some of) the defaults:

```clojure
@timbre/config
=>
{:current-level :debug

 :ns-whitelist []
 :ns-blacklist []

 :middleware [] ; As of Timbre 1.4.0, see source for details

 :timestamp-pattern "yyyy-MMM-dd HH:mm:ss ZZ"
 :timestamp-locale  nil

 :appenders
 {:standard-out        { <...> }
  :spit                { <...> }
  <...> }

 :shared-appender-config {}}
```

Easily adjust the current logging level:

```clojure
(timbre/set-level! :warn)
```

And the default timestamp formatting for log messages:

```clojure
(timbre/set-config! [:timestamp-pattern] "yyyy-MMM-dd HH:mm:ss ZZ")
(timbre/set-config! [:timestamp-locale] (java.util.Locale/GERMAN))
```

Filter logging output by namespaces:
```clojure
(timbre/set-config! [:ns-whitelist] ["some.library.core" "my-app.*"])
```

### Built-in appenders

#### File appender

```clojure
(timbre/set-config! [:appenders :spit :enabled?] true)
(timbre/set-config! [:shared-appender-config :spit-filename] "/path/my-file.log")
```

#### Email ([Postal](https://github.com/drewr/postal)) appender

```clojure
;; [com.draines/postal "1.9.2"] ; Add to project.clj dependencies
;; (:require [taoensso.timbre.appenders (postal :as postal-appender)]) ; Add to ns

(timbre/set-config! [:appenders :postal] postal-appender/postal-appender)
(timbre/set-config! [:shared-appender-config :postal]
                    ^{:host "mail.isp.net" :user "jsmith" :pass "sekrat!!1"}
                    {:from "me@draines.com" :to "foo@example.com"})

;; Rate limit to one email per message per minute
(timbre/set-config! [:appenders :postal :limit-per-msecs] 60000)

;; Make sure emails are sent asynchronously
(timbre/set-config! [:appenders :postal :async?] true)
```

#### IRC ([irclj](https://github.com/flatland/irclj)) appender

```clojure
;; [irclj "0.5.0-alpha2"] ; Add to project.clj dependencies
;; (:require [taoensso.timbre.appenders (irc :as irc-appender)]) ; Add to ns

(timbre/set-config! [:appenders :irc] irc-appender/irc-appender)
(timbre/set-config! [:shared-appender-config :irc]
                    {:host "irc.example.org"
                     :port 6667
                     :nick "logger"
                     :name "Logger"
                     :chan "#logs"})
```

#### Socket ([server-socket](https://github.com/technomancy/server-socket)) appender

Listens on the specified interface (use :all for all interfaces, defaults to localhost if unspecified) and port. Connect with either of:

```
telnet localhost 9000
netcat localhost 9000
```

```clojure
;; [server-socket "1.0.0"] ; Add to project.clj dependencies
;; (:require [taoensso.timbre.appenders (socket :as socket-appender)]) ; Add to ns

(timbre/set-config! [:appenders :socket] socket-appender/socket-appender)
(timbre/set-config! [:shared-appender-config :socket]
                    {:listen-addr :all
                     :port 9000})
```

#### MongoDB ([congomongo](https://github.com/aboekhoff/congomongo)) appender

```clojure
;; [congomongo "0.4.1"] ; Add to project.clj dependencies
;; (:require [taoensso.timbre.appenders (mongo :as mongo-appender)]) ; Add to ns

(timbre/set-config! [:appenders :mongo] mongo-appender/mongo-appender)
(timbre/set-config! [:shared-appender-config :mongo]
                    {:db          "logs"
                     :collection  "myapp"
                     :server      {:host "127.0.0.1" :port 27017}})
```

### Custom appenders

Writing a custom appender is dead-easy:

```clojure
(timbre/set-config!
 [:appenders :my-appender]
 {:doc       "Hello-world appender"
  :min-level :debug
  :enabled?  true
  :async?    false
  :limit-per-msecs nil ; No rate limit
  :fn (fn [{:keys [ap-config level prefix throwable message] :as args}]
        (when-not (:my-production-mode? ap-config)
          (println prefix "Hello world!" message)))
```

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 the `timbre/config` docstring for more information on appenders.

## Profiling

The usual recommendation for Clojure profiling is: use a good **JVM profiler** like [YourKit](http://www.yourkit.com/), [JProfiler](http://www.ej-technologies.com/products/jprofiler/overview.html), or [VisualVM](http://docs.oracle.com/javase/6/docs/technotes/guides/visualvm/index.html).

And these certainly do the job. But as with many Java tools, they can be a little hairy and often heavy-handed - especially when applied to Clojure. Timbre includes an alternative.

Let's add it to our app's `ns` declaration:

```clojure
(:require [taoensso.timbre.profiling :as profiling :refer (p profile)])
```

Wrap forms that you'd like to profile with the `p` macro and give them a name:

```clojure
(defn my-fn
  []
  (let [nums (vec (range 1000))]
    (+ (p :fast-sleep (Thread/sleep 1) 10)
       (p :slow-sleep (Thread/sleep 2) 32)
       (p :add  (reduce + nums))
       (p :sub  (reduce - nums))
       (p :mult (reduce * nums))
       (p :div  (reduce / nums)))))

(my-fn)
=> 42
```

The `profile` macro can now be used to log times for any wrapped forms:

```clojure
(profile :info :Arithmetic (dotimes [n 100] (my-fn)))
=> "Done!"
%> 2012-Jul-03 20:46:17 +0700 localhost INFO [my-app] - Profiling my-app/Arithmetic
              Name  Calls       Min        Max       MAD      Mean  Total% Total
 my-app/slow-sleep    100       2ms        2ms      31μs       2ms      57 231ms
 my-app/fast-sleep    100       1ms        1ms      27μs       1ms      29 118ms
        my-app/add    100      44μs        2ms      46μs     100μs       2 10ms
        my-app/sub    100      42μs      564μs      26μs      72μs       2 7ms
        my-app/div    100      54μs      191μs      17μs      71μs       2 7ms
       my-app/mult    100      31μs      165μs      11μs      44μs       1 4ms
       Unaccounted                                                       6 26ms
             Total                                                     100 405ms
```

It's important to note that Timbre profiling is fully **logging-level aware**: if the  level is insufficient, you *won't pay for profiling*. Likewise, normal namespace filtering applies. (Performance characteristics for both checks are inherited from Timbre itself).

And since `p` and `profile` **always return their body's result** regardless of whether profiling actually happens or not, it becomes feasible to use profiling more often as part of your normal workflow: just *leave profiling code in production as you do for logging code*.

A simple **sampling profiler** is also available: `taoensso.timbre.profiling/sampling-profile`.

## This project supports the CDS and ![ClojureWerkz](https://raw.github.com/clojurewerkz/clojurewerkz.org/master/assets/images/logos/clojurewerkz_long_h_50.png) goals

  * [CDS](http://clojure-doc.org/), the **Clojure Documentation Site**, is a **contributer-friendly** community project aimed at producing top-notch, **beginner-friendly** Clojure tutorials and documentation. Awesome resource.

  * [ClojureWerkz](http://clojurewerkz.org/) is a growing collection of open-source, **batteries-included Clojure libraries** that emphasise modern targets, great documentation, and thorough testing. They've got a ton of great stuff, check 'em out!

## Contact & contribution

Please use the [project's GitHub issues page](https://github.com/ptaoussanis/timbre/issues) for project questions/comments/suggestions/whatever **(pull requests welcome!)**. Am very open to ideas if you have any!

Otherwise reach me (Peter Taoussanis) at [taoensso.com](https://www.taoensso.com) or on Twitter ([@ptaoussanis](https://twitter.com/#!/ptaoussanis)). Cheers!

## License

Copyright &copy; 2012, 2013 Peter Taoussanis. Distributed under the [Eclipse Public License](http://www.eclipse.org/legal/epl-v10.html), the same as Clojure.