Kraken Logging

• Kraken Core's logging system integrates Felix logging, OSGi logging and slf4j logging.

How Integrated Logging Works?

• Felix default logger replacement
  • Kraken embeds Felix framework and start it at boot()
  • Felix constructor has a config map parameter.
  • FelixConstants.LOG_LOGGER_PROP(felix.log.logger) config is set to org.slf4j.Logger
• OSGi Log Service implementation
  • Kraken Core registers KrakenLogService as an OSGi Log Service.

    context.registerService(LogService.class.getName(), new KrakenLogService(), null);
    

  • KrakenLogService implements org.osgi.service.log.LogService.
  • All logs are passed to org.apache.felix.framework.Logger.
  • Then felix logger will send all logs to slf4j logger.
• SLF4J logging
  • KrakenLogger acts as felix logger and slf4j logger.
    • extends org.apache.felix.framework.Logger

      @Override
      protected void doLog(ServiceReference sr, int level, String msg, Throwable throwable) {
      	internalLog(level, msg, throwable);
      }
      

  • implements org.slf4j.Logger

Trace Log in Kraken Console

• You can view logs in realtime using the logger.tail command.
  • INFO to FATAL log level by default.
  • Press Ctrl-C if you want to stop.

    kraken> logger.tail
    ======= Tailing ========
    [2009-09-09 00:40:10.838 INFO ] console opened from: /127.0.0.1:3531
    ...
    waiting monitor stop..
    interrupted.
    

• If you want trace or debug logging, you should set logger.
  • You can list all loggers or filter loggers by prefix matching

    kraken> logger.list
    ==================
     Logger List
    ==================
    org.apache.felix.framework.Felix
    org.krakenapps.bundle.BundleManager
    org.krakenapps.console.ConsoleHandler
    org.krakenapps.main.Kraken
    ...
    kraken> logger.list org.apache.felix
    ==================
     Logger List
    ==================
    org.apache.felix.framework.Felix
    

  • Set logger using the logger.set command

    kraken> logger.set org.apache.felix.framework.Felix debug on
    

  • You can also turn off specific log level

    kraken> logger.set org.apache.felix.framework.Felix debug off
    

How to use SLF4J in my project?

• Kraken Core implements and exports org.slf4j.impl package. (version 1.5.6)
  • You can add slf4j-api 1.5.6 and use slf4j api.

    <dependencies>
    ...
    	<dependency>
    		<groupId>org.slf4j</groupId>
    		<artifactId>slf4j-api</artifactId>
    		<version>1.5.6</version>
    	</dependency>
    ...
    </dependencies>
    

  • But you SHOULD NOT add any slf4j implementation to dependencies.