OSGi/Karaf doesn't find GelfAppender

I try to use Apache Karaf with a Gelf Appender to connect to Log4J, but I just get ClassNotFoundException.

I followed the instructions from Karaf Docs section "Using your own appenders":

I added a folder system/org/graylog2/gelfj/1.1.12/ and copied gelfj-1.1.12.jarfrom Maven repo into the folder. I added this line to etc/startup.properties:

org/graylog2/gelfj/1.1.12/org.graylog2.gelfj-1.1.12.jar=7
org/ops4j/pax/logging/pax-logging-api/1.7.0/pax-logging-api-1.7.0.jar=8

(Second line was already there, I followed the instruction "add the new fragment bundle to the list before the pax-logging-service bundle".)

I also added to file etc/org.ops4j.pax.logging.cfg

# Root logger
log4j.rootLogger=INFO,out,graylog2,osgi:*
...
log4j.appender.graylog2=org.graylog2.log.GelfAppender
log4j.appender.graylog2.graylogHost=foo.bar.de
log4j.appender.graylog2.facility=myall
log4j.appender.graylog2.Threshold=INFO

If I start karaf I just get this exception:

/opt/apache-karaf-2.3.11/bin/karaf server
karaf: JAVA_HOME not set; results may vary
log4j:ERROR Could not instantiate class [org.graylog2.log.GelfAppender].
java.lang.ClassNotFoundException: org.graylog2.log.GelfAppender not found by org.ops4j.pax.logging.pax-logging-service [4]
    at org.apache.felix.framework.BundleWiringImpl.findClassOrResourceByDelegation(BundleWiringImpl.java:1460)
    at org.apache.felix.framework.BundleWiringImpl.access$400(BundleWiringImpl.java:72)
    at org.apache.felix.framework.BundleWiringImpl$BundleClassLoader.loadClass(BundleWiringImpl.java:1843)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:268)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:191)
    at org.apache.log4j.helpers.Loader.loadClass(Loader.java:198)
    at org.apache.log4j.helpers.OptionConverter.instantiateByClassName(OptionConverter.java:326)
    at org.apache.log4j.helpers.OptionConverter.instantiateByKey(OptionConverter.java:123)
    at org.apache.log4j.PaxLoggingConfigurator.parseAppender(PaxLoggingConfigurator.java:97)
    at org.apache.log4j.PropertyConfigurator.parseCategory(PropertyConfigurator.java:735)
    at org.apache.log4j.PropertyConfigurator.parseCatsAndRenderers(PropertyConfigurator.java:639)
    at org.apache.log4j.PropertyConfigurator.doConfigure(PropertyConfigurator.java:504)
    at org.apache.log4j.PaxLoggingConfigurator.doConfigure(PaxLoggingConfigurator.java:72)
    at org.ops4j.pax.logging.service.internal.PaxLoggingServiceImpl.updated(PaxLoggingServiceImpl.java:214)
    at org.ops4j.pax.logging.service.internal.PaxLoggingServiceImpl$1ManagedPaxLoggingService.updated(PaxLoggingServiceImpl.java:362)
    at org.apache.felix.cm.impl.helper.ManagedServiceTracker.updateService(ManagedServiceTracker.java:148)
    at org.apache.felix.cm.impl.helper.ManagedServiceTracker.provideConfiguration(ManagedServiceTracker.java:81)
    at org.apache.felix.cm.impl.ConfigurationManager$ManagedServiceUpdate.provide(ConfigurationManager.java:1436)
    at org.apache.felix.cm.impl.ConfigurationManager$ManagedServiceUpdate.run(ConfigurationManager.java:1392)
    at org.apache.felix.cm.impl.UpdateThread.run(UpdateThread.java:103)
    at java.lang.Thread.run(Thread.java:701)
log4j:ERROR Could not instantiate appender named "graylog2".

I also tried this instructions with the same result.

Thanks for help.

Solution

Taken from the latest gelfj-1.1.12.jar, I can tell it's already a fragment bundle which will attach to the pax-logging-service bundle. A quick install, and refesh of the pax-logging-service bundle result in a successful installation of it. Adding your configuration from above results in a host not found failure.

Therefore as the gelf bundle is already fragment bundle, all it takes is an installation of it via

install mvn:org.graylog2/gelfj/1.1.12

and a

refresh 2

or just do a restart of the container.