= loggability home :: http://deveiate.org/projects/loggability code :: http://bitbucket.org/ged/loggability docs :: http://deveiate.org/code/loggability github :: http://github.com/ged/loggability == Description A composable logging system built on the standard Logger library. You can add Loggability to large libraries and systems, then hook everything up later when you know where you want logs to be written, at what level of severity, and in which format. An example: # Load a bunch of libraries that use Loggability require 'strelka' require 'inversion' require 'treequel' require 'loggability' # Set up our own library module MyProject extend Loggability log_as :my_project class Server extend Loggability log_to :my_project def initialize self.log.debug "Listening." end end end # Now tell everything that's using Loggability to log to an HTML # log file at INFO level Loggability.write_to( '/usr/local/www/htdocs/log.html' ) Loggability.format_as( :html ) Loggability.level = :info === Configurability Loggability has support for the Configurability[https://rubygems.org/gems/configurability] library, which does the same thing for configuration that Loggability does for logging. You can configure all registered loggers from the 'logging' section of the config: logging: __default__: warn STDERR mongrel2: info STDOUT (html) strelka: debug (html) inversion: error /var/log/templating.log (default) The format of the value of each logger is: SEVERITY [TARGET] [(FORMAT)] where: [+SEVERITY+] The log level; one of: +debug+, +info+, +warn+, +error+, or +fatal+ [+TARGET+] The destination for log messages. This can be the path to a log file, or one of 'STDOUT' or 'STDERR', which get mapped to the equivalent filehandle. Optional. [+FORMAT+] The name of one of the formatters. Loggability comes with +default+ (plaintext), +color+ (ANSI colored text), and +html+ formatters. If the special key __default__ is included, its config will be used to set global defaults before the individual configs are applied. If either of the optional values is unspecified, it is left unchanged from what it was before configuration. == Prerequisites * Ruby 1.9.3 or better, Rubinius 2.0 or better It will probably work under any other interpreter in which Logger works, but it's only tested in the above. == Installation $ gem install loggability == Usage Loggability is split up into two parts: {log hosts}[rdoc-ref:Loggability::LogHost] and {log clients}[rdoc-ref:Loggability::LogClient]. A log host is an object that contains a Logger instance that will be used to log stuff. A log client is an object that will write logging messages to a particular log host's Logger. Both parts require that you extend the object with Loggability. === Setting Up A 'Log Host' To install a Logger into an object, you use the +log_as+ declaration with a Symbol that will be used as the key for the object's Logger: module MyProject extend Loggability log_as :my_project end After declaring itself as a log host, it will have an associated Loggability::Logger object that's a wrapper around a Logger instance: MyProject.logger # => # Since it's still a Logger object, you can call all the regular Logger methods: MyProject.logger.level = Logger::WARN MyProject.logger.debug("Created logger") MyProject.logger.info("Program started") MyProject.logger.warn("Nothing to do!") begin File.each_line(path) do |line| unless line =~ /^(\w+) = (.*)$/ MyProject.logger.error("Line in wrong format: #{line}") end end rescue => err MyProject.logger.fatal("Caught exception; exiting") MyProject.logger.fatal(err) end or use a few new convenience methods for changing the logging level: MyProject.logger.level = :debug ...installing a different formatter: MyProject.logger.format_as( :html ) ...changing the output destination: log_messages = [] MyProject.logger.output_to( log_messages ) ...{and more}[rdoc-ref:Loggability::Logger]. === Setting Up A 'Log Client' To add an object that will log to your log host, after you extend Loggability, use the +log_to+ declaration to hook up the object (and instances of the object if you use +log_to+ in a Class) to the log host you specify: class MyProject::Server extend Loggability log_to :my_project def initialize( config={} ) self.log.debug "Creating a server with config: %p" % [ config ] #... end end You can fetch any object's Logger through the Loggability object: Loggability[ MyProject ] # => # Loggability[ MyProject::Server ] # => # Calling the object's #log method will return a Proxy for its host's Logger object that will include the object's name in the log messages 'progname'. You can also use the log host itself as the argument to +log_to+: class MyProject::Client extend Loggability log_to MyProject end === Aggregate Logging If you have several log hosts, and you want to affect them all simultaneously, you can do that using the aggregate functions of Loggability. They're the same as the methods on Loggability::Logger: # Set all logs to log at INFO level Loggability.level = :info # Write HTML logs Loggability.format_with( :html ) # Log everything to the same logfile Loggability.output_to( "/tmp/my_project_log.html" ) === Temporarily Overriding Logging Behavior Sometimes you want to log one particular chunk of code at a different level, or to a different destination, and then restore everything back to the way it was afterwards. Loggability has a few ways of doing that: # Log only fatal errors... Loggability.with_level( :fatal ) do ... end # Log everything to an array for the block logs = [] Loggability.outputting_to( logs ) do ... end # Log using the HTML formatter Loggability.formatted_with( :html ) do ... end # Or chain them together: Loggability.with_level( :debug ).outputting_to( $stderr ).formatted_with( :color ) do Client.connect! end == Contributing You can check out the current development source with Mercurial[http://bitbucket.org/ged/loggability], or if you prefer Git, via {its Github mirror}[https://github.com/ged/loggability]. After checking out the source, run: $ rake newb This task will install any missing dependencies, run the tests/specs, and generate the API documentation. == License Copyright (c) 2012, Michael Granger All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: * Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. * Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. * Neither the name of the author/s, nor the names of the project's contributors may be used to endorse or promote products derived from this software without specific prior written permission. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.