timbre/README.md

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**[CHANGELOG]** | [API] | current [Break Version]:
```clojure
[com.taoensso/timbre "4.5.1"] ; Stable
```
> Please consider helping to [support my continued open-source Clojure/Script work]?
>
> Even small contributions can add up + make a big difference to help sustain my time writing, maintaining, and supporting Timbre and other Clojure/Script libraries. **Thank you!**
>
> \- Peter Taoussanis
# Timbre
## A pure Clojure/Script logging library
Java logging is a Kafkaesque mess of complexity that buys you _nothing_. It can be comically hard to get even the simplest logging working, and it just gets worse at scale.
Timbre offers an **all Clojure/Script** alternative that's fast, deeply flexible, easy to configure, and that **works out the box**. No XML.
Supports optional interop with [tools.logging](https://github.com/ptaoussanis/timbre/blob/master/src/taoensso/timbre/tools/logging.clj) and [log4j/logback/slf4j](https://github.com/fzakaria/slf4j-timbre).
Happy hacking!
## Features
* Full **Clojure** + **ClojureScript** support (v4+).
* No XML or properties files. **A single, simple config map**, and you're set.
* Simple, flexible **fn appender model** with **middleware**.
* **Great performance** at any scale.
* Filter logging by levels, **namespace whitelist/blacklist patterns**, and more.
* **Zero overhead** with **complete Clj+Cljs elision** for compile-time level/ns filters.
* Includes a simple, high-performance **[logging profiler][]**.
* Useful built-in appenders for **out-the-box** Clj+Cljs logging.
* Powerful, easy-to-configure **rate limits** and **async logging**.
* [Logs as Clojure values][] (v3+).
* Small, simple, cross-platform codebase.
## 3rd-party tools, appenders, etc.
Link | Description
------------------------ | -----------------------------------------------------
[@fzakaria/slf4j-timbre] | Route log4j/logback/sfl4j log output to Timbre
[@palletops/log-config] | Library to help manage Timbre logging config
Your link here? | **PR's welcome!**
## Getting started
Add the necessary dependency to your project:
```clojure
[com.taoensso/timbre "4.5.1"]
```
And setup your namespace imports:
```clojure
(ns my-clj-ns ; Clojure namespace
(:require
[taoensso.timbre :as timbre
:refer (log trace debug info warn error fatal report
logf tracef debugf infof warnf errorf fatalf reportf
spy get-env log-env)]
[taoensso.timbre.profiling :as profiling
:refer (pspy p defnp profile)]))
(ns my-cljs-ns ; ; ClojureScript namespace
(:require
[taoensso.timbre :as timbre
:refer-macros (log trace debug info warn error fatal report
logf tracef debugf infof warnf errorf fatalf reportf
spy get-env log-env)]))
```
> You can also call `(timbre/refer-timbre)` to configure Clj ns referrals **automatically**.
### Logging
By default, Timbre gives you basic `println` and `js/console` (v4+) output at a `:debug` log level:
```clojure
(info "This will print") => nil
%> 15-Jun-13 19:18:33 localhost INFO [my-app.core] - This will print
(spy :info (* 5 4 3 2 1)) => 120
%> 15-Jun-13 19:19:13 localhost INFO [my-app.core] - (* 5 4 3 2 1) => 120
(defn my-mult [x y] (info "Lexical env:" (get-env)) (* x y)) => #'my-mult
(my-mult 4 7) => 28
%> 15-Jun-13 19:21:53 localhost INFO [my-app.core] - Lexical env: {x 4, y 7}
(trace "This won't print due to insufficient log level") => nil
```
First-argument exceptions generate a nicely cleaned-up stack trace using [io.aviso.exception][] (Clj only):
```clojure
(info (Exception. "Oh noes") "arg1" "arg2")
%> 15-Jun-13 19:22:55 localhost INFO [my-app.core] - arg1 arg2
java.lang.Exception: On noes
<Stacktrace>
```
Other utils include: `log-errors`, `log-and-rethrow-errors`, `logged-future`, and `handle-uncaught-jvm-exceptions!` (please see the [API] for details).
#### Disabling stacktrace colors
ANSI colors are enabled by default for stacktraces. To turn these off (e.g. for log files or emails), you can add the following entry to your top-level config **or** individual appender map/s:
```clojure
:output-fn (partial timbre/default-output-fn {:stacktrace-fonts {}})
```
And/or you can set the `TIMBRE_DEFAULT_STACKTRACE_FONTS` environment variable (supports edn).
### Configuration
This is the biggest win over Java logging IMO. **All** of Timbre's behaviour is controlled through a single, simple Clojure map.
> See `timbre/example-config` for Timbre's default config map
```clojure
(def example-config
"An example Timbre v4 config map.
APPENDERS
An appender is a map with keys:
:min-level ; Level keyword, or nil (=> no minimum level)
:enabled? ;
:async? ; Dispatch using agent? Useful for slow appenders (clj only)
:rate-limit ; [[ncalls-limit window-ms] <...>], or nil
:output-fn ; Optional override for inherited (fn [data]) -> string
:timestamp-opts ; Optional override for inherited {:pattern _ :locale _ :timezone _}
:ns-whitelist ; Optional, stacks with active config's whitelist
:ns-blacklist ; Optional, stacks with active config's blacklist
:fn ; (fn [data]) -> side effects, with keys described below
An appender's fn takes a single data map with keys:
:config ; Entire config map (this map, etc.)
:appender-id ; Id of appender currently dispatching
:appender ; Entire map of appender currently dispatching
:instant ; Platform date (java.util.Date or js/Date)
:level ; Keyword
:error-level? ; Is level e/o #{:error :fatal}?
:?ns-str ; String, or nil
:?file ; String, or nil
:?line ; Integer, or nil ; Waiting on CLJ-865
:?err ; First-arg platform error, or nil
:vargs ; Vector of raw args
:output_ ; Forceable - final formatted output string created
; by calling (output-fn <this-data-map>)
:msg_ ; Forceable - args as a string
:timestamp_ ; Forceable - string
:hostname_ ; Forceable - string (clj only)
:output-fn ; (fn [data]) -> formatted output string
; (see `default-output-fn` for details)
:context ; *context* value at log time (see `with-context`)
:profile-stats ; From `profile` macro
**NB** - any keys not specifically documented here should be
considered private / subject to change without notice.
MIDDLEWARE
Middleware are simple (fn [data]) -> ?data fns (applied left->right) that
transform the data map dispatched to appender fns. If any middleware
returns nil, NO dispatch will occur (i.e. the event will be filtered).
The `example-config` source code contains further settings and details.
See also `set-config!`, `merge-config!`, `set-level!`."
{:level :debug ; e/o #{:trace :debug :info :warn :error :fatal :report}
;; Control log filtering by namespaces/patterns. Useful for turning off
;; logging in noisy libraries, etc.:
:ns-whitelist [] #_["my-app.foo-ns"]
:ns-blacklist [] #_["taoensso.*"]
:middleware [] ; (fns [data]) -> ?data, applied left->right
;; Clj only:
:timestamp-opts default-timestamp-opts ; {:pattern _ :locale _ :timezone _}
:output-fn default-output-fn ; (fn [data]) -> string
:appenders
{;; The standard println appender:
;; :println (println-appender {:stream :auto})
:an-example-custom-println-appender
;; Inline appender definition (just a map):
{:enabled? true
:async? false
:min-level nil
:rate-limit [[1 250] [10 5000]] ; 1/250ms, 10/5s
:output-fn :inherit
:fn ; Appender's (fn [data]) -> side effects
(fn [data]
(let [{:keys [output_]} data
formatted-output-str (force output_)]
(println formatted-output-str)))}}})
```
A few things to note:
* Appenders are _trivial_ to write & configure - **they're just fns**. It's Timbre's job to dispatch useful args to appenders when appropriate, it's their job to do something interesting with them.
* Being 'just fns', appenders have basically limitless potential: write to your database, send a message over the network, check some other state (e.g. environment config) before making a choice, etc.
#### Log levels and ns filters
The **log level** may be set:
* At compile-time: (`TIMBRE_LEVEL` environment variable).
* Statically using: `timbre/set-level!`/`timbre/merge-level!`.
* Dynamically using: `timbre/with-level`.
The **ns filters** may be set:
* At compile-time: (`TIMBRE_NS_WHITELIST`, `TIMBRE_NS_BLACKLIST` env vars).
* Statically using: `timbre/set-config!`/`timbre/merge-config!`.
* Dynamically using: `timbre/with-config`.
There are also variants of the core logging macros that take an **explicit config arg**:
```clojure
(timbre/log* <config-map> <level> <& args>) ; or
(timbre/logf* <config-map> <level> <& args>)
```
Logging calls excluded by a compile-time option (e.g. during Cljs compilation) will be **entirely elided from your codebase**, e.g.:
```bash
#!/bin/bash
# edn values welcome:
export TIMBRE_LEVEL=':warn' # Elide all lower logging calls
export TIMBRE_NS_WHITELIST='["my-app.*"]' # Elide all other ns logging calls
export TIMBRE_NS_BLACKLIST='["my-app.foo" "my-app.bar.*"]'
lein cljsbuild once # Compile js with appropriate logging calls excluded
lein uberjar # Compile jar ''
```
### Built-in appenders
#### Redis ([Carmine]) appender (v3+)
```clojure
;; [com.taoensso/carmine <latest-version>] ; Add to project.clj deps
;; (:require [taoensso.timbre.appenders (carmine :as car-appender)]) ; Add to ns
(timbre/merge-config! {:appenders {:carmine (car-appender/carmine-appender)}})
```
This gives us a high-performance Redis appender:
* **All raw logging args are preserved** in serialized form (even errors).
* Configurable number of entries to keep per log level.
* Only the most recent instance of each **unique entry** is kept.
* Resulting **log is just a Clojure value**: a vector of log entries (maps).
Clojure has a rich selection of built-in and 3rd party tools for querying values like this.
See also `car-appender/query-entries`.
#### Email ([Postal]) appender
```clojure
;; [com.draines/postal <latest-version>] ; Add to project.clj deps
;; (:require [taoensso.timbre.appenders (postal :as postal-appender)]) ; Add to ns
(timbre/merge-config!
{:appenders
{:postal
(postal-appender/postal-appender
^{:host "mail.isp.net" :user "jsmith" :pass "sekrat!!1"}
{:from "me@draines.com" :to "foo@example.com"})}})
```
#### File appender
```clojure
;; (:require [taoensso.timbre.appenders.core :as appenders]) ; Add to ns
(timbre/merge-config!
{:appenders {:spit (appenders/spit-appender {:fname "/path/my-file.log"})}})
```
#### Other included appenders
A number of 3rd-party appenders are included out-the-box [here](https://github.com/ptaoussanis/timbre/tree/master/src/taoensso/timbre/appenders/3rd_party). **Please see the relevant docstring for details**. Thanks goes to the respective authors!
Just give me a shout if you've got an appender you'd like to have added.
## Profiling
> Currently Clj only
The usual recommendation for Clojure profiling is: use a good **JVM profiler** like [YourKit], [JProfiler], or [VisualVM].
And these can certainly do the job. But as with many Java tools, they can be a little hairy and often heavy-handed. Timbre includes a simple, lightweight alternative.
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
```
Timbre profiling is **log level & ns filter aware**: if the level is insufficient or ns filtered, you **won't pay for profiling**.
And since `p` and `profile` **always return their body's result**, it becomes feasible to use profiling more often as part of your normal workflow: just *leave profiling code in production as you do logging code*.
See also `defnp`, `sampling-profile`.
## This project supports the ![ClojureWerkz-logo] goals
[ClojureWerkz] is a growing collection of open-source, **batteries-included Clojure libraries** that emphasise modern targets, great documentation, and thorough testing.
## Contacting me / contributions
Please use the project's [GitHub issues page] for all questions, ideas, etc. **Pull requests welcome**. See the project's [GitHub contributors page] for a list of contributors.
Otherwise, you can reach me at [Taoensso.com]. Happy hacking!
\- [Peter Taoussanis]
## License
Distributed under the [EPL v1.0] \(same as Clojure).
Copyright &copy; 2015-2016 [Peter Taoussanis].
<!--- Standard links -->
[Taoensso.com]: https://www.taoensso.com
[Peter Taoussanis]: https://www.taoensso.com
[@ptaoussanis]: https://www.taoensso.com
[More by @ptaoussanis]: https://www.taoensso.com
[Break Version]: https://github.com/ptaoussanis/encore/blob/master/BREAK-VERSIONING.md
[support my continued open-source Clojure/Script work]: http://taoensso.com/clojure/backers
<!--- Standard links (repo specific) -->
[CHANGELOG]: https://github.com/ptaoussanis/timbre/releases
[API]: http://ptaoussanis.github.io/timbre/
[GitHub issues page]: https://github.com/ptaoussanis/timbre/issues
[GitHub contributors page]: https://github.com/ptaoussanis/timbre/graphs/contributors
[EPL v1.0]: https://raw.githubusercontent.com/ptaoussanis/timbre/master/LICENSE
[Hero]: https://raw.githubusercontent.com/ptaoussanis/timbre/master/hero.png "Title"
<!--- Unique links -->
[logging profiler]: #profiling
[Logs as Clojure values]: #redis-carmine-appender-v3
[@palletops/log-config]: https://github.com/palletops/log-config
[@fzakaria/slf4j-timbre]: https://github.com/fzakaria/slf4j-timbre
[io.aviso.exception]: https://github.com/AvisoNovate/pretty
[Carmine]: https://github.com/ptaoussanis/carmine
[Postal]: https://github.com/drewr/postal
[YourKit]: http://www.yourkit.com/)
[JProfiler]: http://www.ej-technologies.com/products/jprofiler/overview.html
[VisualVM]: http://docs.oracle.com/javase/6/docs/technotes/guides/visualvm/index.html
[ClojureWerkz-logo]: https://raw.github.com/clojurewerkz/clojurewerkz.org/master/assets/images/logos/clojurewerkz_long_h_50.png
[ClojureWerkz]: http://clojurewerkz.org/