Yell - Your Extensible Logging Library is a comprehensive logging replacement for Ruby.
Yell works and its test suite currently runs on:
- ruby-head, 2.3.1, 2.2.5, 2.2.2, 2.1.0, 2.0.0
- jruby-head, jruby-126.96.36.199, jruby-188.8.131.52
If you want to conveniently use Yell with Rails, then head over to yell-rails. You'll find all the documentation in this repository, though.
gem install yell
Or in your Gemfile:
On the basics, you can use Yell just like any other logging library with a more sophisticated message formatter.
logger = Yell.new STDOUT logger.info "Hello World" #=> "2012-02-29T09:30:00+01:00 [ INFO] 65784 : Hello World" # ^ ^ ^ ^ # ISO8601 Timestamp Level Pid Message
The strength of Yell, however, comes when using multiple adapters. The already built-in ones are IO-based and require no further configuration. Also, there are additional ones available as separate gems. Please consult the wiki on that - they are listed there.
The standard adapters are:
:stdout : Messages will be written to STDOUT
:stderr : Messages will be written to STDERR
:file : Messages will be written to a file
:datefile : Messages will be written to a timestamped file
Here are some short examples on how to combine them:
Example: Notice messages go into
STDOUT and error messages into
logger = Yell.new do |l| l.adapter STDOUT, level: [:debug, :info, :warn] l.adapter STDERR, level: [:error, :fatal] end
Example: Typical production Logger
We setup a logger that starts passing messages at the
:info level. Severities
:error go into the 'production.log', whereas anything higher is written
into the 'error.log'.
logger = Yell.new do |l| l.level = 'gte.info' # will only pass :info and above to the adapters l.adapter :datefile, 'production.log', level: 'lte.warn' # anything lower or equal to :warn l.adapter :datefile, 'error.log', level: 'gte.error' # anything greater or equal to :error end
Example: Typical production Logger for Heroku
When deploying to Heroku, the "rails_log_stdout" gem gets injected to your Rails project. Yell does not need that when properly configured (see yell-rails for a more convenient integration with Rails).
logger = Yell.new do |l| l.level = 'gte.info' l.adapter :stdout, level: 'lte.warn' l.adapter :stderr, level: 'gte.error' end
But I'm used to Log4r and I don't want to move on
One of the really nice features of Log4r is its repository. The following example is taken from the official Log4r documentation.
require 'log4r' include Log4r # create a logger named 'mylog' that logs to stdout mylog = Logger.new 'mylog' mylog.outputters = Outputter.stdout # later in the code, you can get the logger back Logger['mylog']
With Yell you can do the same thing with less:
require 'yell' # create a logger named 'mylog' that logs to stdout Yell.new :stdout, name: 'mylog' # later in the code, you can get the logger back Yell['mylog']
There is no need to define outputters separately and you don't have to taint you global namespace with Yell's subclasses.
Adding a logger to an existing class
Yell comes with a simple module: +Yell::Loggable+. Simply include this in a class and you are good to go.
# Before you can use it, you will need to define a logger and # provide it with the `:name` of your class. Yell.new :stdout, name: 'Foo' class Foo include Yell::Loggable end # Now you can log Foo.logger.info "Hello World" Foo.new.logger.info "Hello World"
It even works with class inheritance:
# Given the above example, we inherit from Foo class Bar < Foo end # The logger will fallback to the Foo superclass Bar.logger.info "Hello World" Bar.new.logger.info "Hello World"
Adding a logger to all classes at once (global logger)
Derived from the example above, simply do the following.
# Define a logger and pass `Object` as name. Internally, Yell adds this # logger to the repository where you can access it later on. Yell.new :stdout, name: Object # Enable logging for the class that (almost) every Ruby class inherits from Object.send :include, Yell::Loggable # now you are good to go... from wherever you are logger.info "Hello from anything" Integer.logger.info "Hello from Integer"
Suppress log messages with silencers
In case you woul like to suppress certain log messages, you may define silencers with Yell. Use this to get control of a noisy log environment. For instance, you can suppress logging messages that contain secure information or more simply, to skip information about serving your Rails assets. Provide a string or a regular expression of the message patterns you would like to exclude.
logger = Yell.new do |l| l.silence /^Started GET "\/assets/ l.silence /^Served asset/ end logger.debug 'Started GET "/assets/logo.png" for 127.0.0.1 at 2013-06-20 10:18:38 +0200' logger.debug 'Served asset /logo.png - 304 Not Modified (0ms)'
Alter log messages with modifiers
You can find further examples and additional adapters in the wiki. or have a look into the examples folder.
Copyright © 2011-current Rudolf Schmidt, released under the MIT license