Amichai Rothman created AMQ-4774:
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Summary: ActiveMQ broker silently fails to start in Karaf
Key: AMQ-4774
URL: https://issues.apache.org/jira/browse/AMQ-4774
Project: ActiveMQ
Issue Type: Bug
Components: OSGi/Karaf
Affects Versions: 5.8.0
Environment: Karaf 2.3.3
Reporter: Amichai Rothman
I have an application, deployed into Karaf. I install the activemq-broker
feature, and one of the app bundles uses ActiveMQConnectionFactory to get a
javax.jms.Connection instance and then uses the JMS API only (no other
ActiveMQ-specific APIs in use). I'll note that this bundle depends on another
bundle which uses the JMS API as well (no ActiveMQ imports there at all). The
application also depends on other karaf features such as cxf-dosgi.
ActiveMQ fails to start in a couple of ways, depending on the order of
installation of the features and app:
At first I got a LinkageError:
java.lang.LinkageError: loader constraint violation: when resolving method
"org.apache.activemq.ActiveMQConnectionFactory.createConne
ction()Ljavax/jms/Connection;" the class loader (instance of
org/eclipse/osgi/internal/baseadaptor/DefaultClassLoader) of the current
class, com/myprojectgroup/bus/activemq/ActiveMQSession, and the class loader
(instance of org/eclipse/osgi/internal/baseadaptor/D
efaultClassLoader) for resolved class,
org/apache/activemq/ActiveMQConnectionFactory, have different Class objects for
the type Ljava
x/jms/Connection; used in the signature
at
com.myprojectgroup.bus.activemq.ActiveMQSession.createConnection(ActiveMQSession.java:38)
at
com.myprojectgroup.messaging.jms.Session.open(Session.java:70)[68:com.myprojectgroup.messaging:0.1.0.SNAPSHOT]
at
com.myprojectgroup.messaging.jms.Session$1.run(Session.java:108)[68:com.myprojectgroup.messaging:0.1.0.SNAPSHOT]
The only bundle that exports the javax.jms package is
org.apache.geronimo.specs.geronimo-jms_1.1_spec, though after further
investigation I found that the activemq-web-console bundle does have another
copy of it internally, which I think might be the cause of the conflict (it
does not import the package in the manifest, so I can't just remove the package
from the jar since it won't find the package exported by the geronimo-jms
bundle without a corresponding import declaration). The activemq-osgi bundle
has a DynamicImport-Package: *, which may further complicate things. If it also
had an explicit Import-Package directive for the statically-linked classes it
uses such as javax.jms ones, perhaps it would go through the regular bundle
classloading mechanism and avoid the problem - I think it takes precedence over
dynamic imports, though I'm not sure).
Next, I played around with reordering the installation, and got to another
failure mode where there is no exception at all or any error in the logs, but
the broker simply fails to start silently. Perhaps this is also caused by
classloader issues but they are just occurring somewhere within ActiveMQ and
being silently ignored. This mode of failure I've managed to recreate easily:
On a fresh stock installation of Karaf 2.3.3, add two feature urls:
features:addurl mvn:org.apache.activemq/activemq-karaf/5.8.0/xml/features
mvn:org.apache.cxf.dosgi/cxf-dosgi/1.6-SNAPSHOT/xml/features
(you might need to add the apache snapshot repo to karaf for it to find the
dosgi snapshot feature)
And then install them in this order:
features:install -v cxf-dosgi-discovery-distributed activemq-broker
The broker will not be started, although the logs will have no errors.
Strangely, if you now uninstall the activemq-web-console bundle (not feature)
and restart karaf, the broker will start ok. Also if you install only
activemq-broker and not dosgi, it will start ok.
To simplify, I found that instead of the dosgi feature it's enough to install
and start the mvn:org.osgi/org.osgi.compendium/4.3.1 bundle before installing
activemq-broker to make it fail - this is from looking at the innards of the
dosgi feature, however if I remove this bundle from the feature the broker
still fails to start, so it's not the only bundle causing problems, but just an
example.
The only workaround I've found so far is to install everything, then uninstall
the activemq-web-console bundle and restart - then everything works as it
should. Strangely, not installing it in the first place doesn't work either -
the broker won't start unless the web console is first started, then
uninstalled.
Some details of the LinkageError are in http://pastebin.com/TKZt7hUA (pasted to
irc channel originally).
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