Log4jruby

• https://github.com/lenny/log4jruby

Description:

Log4jruby is a thin wrapper around the Log4j Logger. It is geared more toward those who are using JRuby to integrate with and build on top of Java code that uses Log4j. The Log4jruby::Logger provides an interface much like the standard ruby Logger. Logging is configured via traditional Log4j methods.

The primary use case (i.e., mine) for this library is that you are already up and running with Log4j and now you want to use it for your Ruby code too. There is not much help here for configuration. In our environment, we deploy Rails apps that call and extend Java code into Tomcat as WARs and use a log4j.properties to configure. For the most part, all there is to using log4jruby is making sure the log4j jar is required and that Log4j is at least minimally configured (e.g., log4j.properties in the CLASSPATH). The examples should give you the idea.

Features

• Filename, line number, and method name are available (if tracing is on) to your appender layout via MDC.
• Exceptions can be logged directly and are output with backtraces. Java Exceptions (i.e., NativeExceptions) are logged with full java backtrace(including nested exceptions).
• Logging config for your ruby code can be added to your existing configuration. Ruby logger names are mapped to dot separated names prefixed with .jruby

 log4j.appender.Ruby=org.apache.log4j.ConsoleAppender
 log4j.appender.Ruby.layout=org.apache.log4j.PatternLayout
 log4j.appender.Ruby.layout.ConversionPattern=%5p %.50X{fileName} %X{methodName}:%X{lineNumber} - %m%n
 ...
 log4j.logger.jruby=info,Ruby
 log4j.logger.jruby.MyClass=debug

Configuration

As noted above, configuring log4j is left to the client. You must load and configure log4j before requiring log4jruby. There are multiple ways to do so. In our environment, we deploy Rails apps that call and extend Java code to Tomcat as WAR files. We provision our app servers with log4j.jar and a log4j.properties file in in $TOMCAT_HOME/lib. You may also add log4j.jar and path to config file into CLASSPATH via environment variables, JAVA_OPTS, JAVA_OPTS, etc... Or add them into $CLASSPATH at runtime before loading log4jruby. See examples/setup.rb.

Note: If you're using bundler, you can specify gem 'log4jruby', require: false in your Gemfile to delay loading the gem too early.

In a Rails application, add the following in config/application.rb or the appropriate config/environments file.

 config.logger = ActiveSupport::TaggedLogging.new(Log4jruby::Logger.get('MyApp'))

or older versions of Rails

 config.logger = Log4jruby::Logger.get('MyApp')

Examples

 def foo
   logger.debug("hello from foo")
   bar
 rescue => e
   logger.error(e)
 end

 DEBUG jruby.MyClass foo:17 - hello from foo
 DEBUG jruby.MyClass bar:24 - hello from bar
 DEBUG jruby.MyClass baz:29 - hello from baz
 ERROR jruby.MyClass foo:20 - error from baz
   examples/simple.rb:30:in `baz'
   examples/simple.rb:25:in `bar'
   examples/simple.rb:18:in `foo'
   examples/simple.rb:35:in `(root)'

See more in log4jruby/examples.

Usage

 class MyClass
   enable_logger

   class << self
     def my_class_method
       logger.info("hello from class method")
     end
   end

   def my_method
     logger.info("hello from instance method")
   end
 end

 INFO jruby.MyModule.A my_class_method:14 - hello from class method
 INFO jruby.MyModule.A my_method:19 - hello from instance method

See more in log4jruby/examples.. They should be runnable from the source.