Re: @Requires : ServiceFactory.getService() resulted in a cycle.

Clement Escoffier Wed, 23 Sep 2009 10:21:34 -0700

Hi,

By analyzing more deeply your stack trace, it seems that during thepojo object creation, the service is unregistered. Do you have anyexplication of such behavior. For sure, this kind of sequence mayannoy the Service Factories.

The immediate should not impact the instance creation. However, it ispossible that something really wrong arrives during the objectcreation of SerialRxTx. In such case, iPOJO stops the instance... Thatmay explain the stack trace. The question is now : why the SerialRxtxPOJO objects cannot be created correctly. Could you try to create themindependently and see if you have an error ?


Regards,

Clement

On 23.09.2009, at 19:02, Joel Schuster wrote:

Clement,

I have an rxtx bundle. I use cfg files to create one or more ipojoinstances of my rxtx service. These cfg files have stuff like baud,parity, com port name, etc.

I have another bundle that uses just one of those, I get the list ofall of them and then pick one based on a property within the rxtxservice also configured by the cfg files.


So:

KNClient (instance from cfg file)
        |
        V
<uses one of x number based on property set in rxtx cfg file>
        |
        V
SerialRxTx (instances from cfg files)

I tried putting immediate=true on the RxTx service, however the cfgfiles no longer were setting the properties and the arch command nolonger showed any instances being created even though theconstructor for the service was being called. As the KNClient is nota service, just a component, it is automatically immediate.


Thanks for your help!

- Joel

-----Original Message-----
From: Clement Escoffier [mailto:[email protected]]
Sent: Wednesday, September 23, 2009 12:53 AM
To: [email protected]

Subject: Re: @Requires : ServiceFactory.getService() resulted in acycle.


Hi,

It sounds like a cycle during object creation. iPOJO object are

created when needed by default (if your component provides aservice).

To handle that iPOJO uses OSGi service factories.

The problem sounds to be the following:
- a service is going to be used
- iPOJO creates the pojo object (because, we need it)
- this object can also depending on a service, which may use the one
of the previous ones.... Cycle

To break the cycle, you can set one component to immediate. In that
case, the object will be created eagerly. the big question is : Which
ones.

If you gives me more detail on your system, I can figure out how to
break the cycle.

Regards,

Clement

On 22.09.2009, at 23:21, Joel Schuster wrote:



I hate sending stack traces but I'm running into a real nasty issue.
I've tried both Felix 1.8.x and 2.0. I get the same issue. I've
tried various forms of the @Requires annotation.

This problem is sometimes reproducible on two systems but not on the
third so I'm beginning to suspect a race condition of some sort as
it only manifests some of the time and is sometimes dependant upon
the order of the bundle loading.

I have one bundle that @Requires a collection of instances from
another bundle that implements two different interfaces, also each
in their own bundles. I've created a test set of bundles to see if
the problem comes from the inheritance model, but I can't reproduce
in a smaller example. Yet another reason it feels like a race
condition.

Thoughts?




-> ERROR: EventDispatcher: Error during dispatch.
(java.lang.IllegalStateException: ServiceFactory.getService()
resulted in a cycle.)
java.lang.IllegalStateException: ServiceFactory.getService()
resulted in a cycle.
        at
org
.apache

.felix.framework.ServiceRegistry.getService(ServiceRegistry.java:261)

        at org.apache.felix.framework.Felix.getService(Felix.java:2881)
        at
org
.apache

.felix.framework.BundleContextImpl.getService(BundleContextImpl.java:

357)

atorg.apache.felix.ipojo.IPojoContext.getService(IPojoContext.java:

260)
        at org.apache.felix.ipojo.util.Tracker.getService(Tracker.java:434)
        at
org
.apache
.felix.ipojo.util.DependencyModel.ungetService(DependencyModel.java:
917)
        at
org
.apache
.felix

.ipojo.util.DependencyModel.manageDeparture(DependencyModel.java:435)

        at
org
.apache
.felix
.ipojo.util.DependencyModel.removedService(DependencyModel.java:424)

at org.apache.felix.ipojo.util.Tracker$Tracked.untrack(Tracker.java:

736)
        at org.apache.felix.ipojo.util.Tracker
$Tracked.serviceChanged(Tracker.java:636)
        at
org
.apache
.felix
.framework
.util
.EventDispatcher.invokeServiceListenerCallback(EventDispatcher.java:
878)
        at
org
.apache
.felix
.framework
.util.EventDispatcher.fireEventImmediately(EventDispatcher.java:732)
        at
org
.apache
.felix
.framework
.util.EventDispatcher.fireServiceEvent(EventDispatcher.java:662)
        at

org.apache.felix.framework.Felix.fireServiceEvent(Felix.java:3603)

        at org.apache.felix.framework.Felix.access$000(Felix.java:40)

at org.apache.felix.framework.Felix$1.serviceChanged(Felix.java:624)

        at
org
.apache
.felix

.framework.ServiceRegistry.unregisterService(ServiceRegistry.java:117)

        at
org
.apache
.felix
.framework

.ServiceRegistrationImpl.unregister(ServiceRegistrationImpl.java:128)

        at
org
.apache
.felix
.ipojo
.handlers
.providedservice
.ProvidedService.unregisterService(ProvidedService.java:298)
        at
org
.apache
.felix
.ipojo
.handlers
.providedservice
.ProvidedServiceHandler.__stateChanged(ProvidedServiceHandler.java:
435)
        at
org
.apache
.felix
.ipojo
.handlers
.providedservice
.ProvidedServiceHandler.stateChanged(ProvidedServiceHandler.java)
        at

org.apache.felix.ipojo.InstanceManager.setState(InstanceManager.java:

451)

atorg.apache.felix.ipojo.InstanceManager.stop(InstanceManager.java:

340)
        at org.apache.felix.ipojo.util.Property.invoke(Property.java:502)
        at
org
.apache
.felix
.ipojo
.handlers
.configuration
.ConfigurationHandler.__onCreation(ConfigurationHandler.java:432)
        at
org
.apache
.felix
.ipojo
.handlers
.configuration
.ConfigurationHandler.onCreation(ConfigurationHandler.java)
        at
org
.apache
.felix.ipojo.InstanceManager.getPojoObject(InstanceManager.java:787)
        at org.apache.felix.ipojo.handlers.providedservice.ProvidedService
$SingletonStrategy.getService(ProvidedService.java:438)
        at
org
.apache
.felix
.ipojo
.handlers

.providedservice.ProvidedService.getService(ProvidedService.java:263)

        at
org
.apache
.felix
.framework
.ServiceRegistrationImpl
.getFactoryUnchecked(ServiceRegistrationImpl.java:293)
        at
org
.apache
.felix
.framework

.ServiceRegistrationImpl.getService(ServiceRegistrationImpl.java:207)

        at
org
.apache

.felix.framework.ServiceRegistry.getService(ServiceRegistry.java:307)

        at org.apache.felix.framework.Felix.getService(Felix.java:2881)
        at
org
.apache

.felix.framework.BundleContextImpl.getService(BundleContextImpl.java:

357)

atorg.apache.felix.ipojo.IPojoContext.getService(IPojoContext.java:

260)
        at org.apache.felix.ipojo.util.Tracker.getService(Tracker.java:426)
        at
org
.apache

.felix.ipojo.util.DependencyModel.getService(DependencyModel.java:901)

        at
org
.apache
.felix
.ipojo
.handlers.dependency.Dependency.createServiceObject(Dependency.java:
481)
        at
org
.apache

.felix.ipojo.handlers.dependency.Dependency.onGet(Dependency.java:456)

at

org.apache.felix.ipojo.InstanceManager.onGet(InstanceManager.java:944)

at

com.navsys.mcmpge.kearfott.knclient.KNClient.__getcomms(KNClient.java)

at

com.navsys.mcmpge.kearfott.knclient.KNClient.<init>(KNClient.java:49)

        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native
Method)
        at
sun
.reflect
.NativeConstructorAccessorImpl
.newInstance(NativeConstructorAccessorImpl.java:39)
        at
sun
.reflect
.DelegatingConstructorAccessorImpl
.newInstance(DelegatingConstructorAccessorImpl.java:27)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
        at
org
.apache
.felix.ipojo.InstanceManager.createObject(InstanceManager.java:600)
        at
org
.apache
.felix.ipojo.InstanceManager.getPojoObject(InstanceManager.java:776)
        at
org
.apache
.felix
.ipojo
.handlers
.lifecycle
.callback
.LifecycleCallbackHandler
.__stateChanged(LifecycleCallbackHandler.java:156)
        at
org
.apache
.felix
.ipojo
.handlers
.lifecycle
.callback

.LifecycleCallbackHandler.stateChanged(LifecycleCallbackHandler.java)

at

org.apache.felix.ipojo.InstanceManager.setState(InstanceManager.java:

440)
        at

org.apache.felix.ipojo.InstanceManager.start(InstanceManager.java:321)

        at
org
.apache
.felix.ipojo.ComponentFactory.createInstance(ComponentFactory.java:
155)
        at
org
.apache
.felix.ipojo.IPojoFactory.createComponentInstance(IPojoFactory.java:
298)
        at
org
.apache
.felix.ipojo.IPojoFactory.createComponentInstance(IPojoFactory.java:
235)
        at

org.apache.felix.ipojo.IPojoFactory.updated(IPojoFactory.java:603)

        at org.apache.felix.cm.impl.ConfigurationManager
$UpdateConfiguration.run(ConfigurationManager.java:1460)
        at org.apache.felix.cm.impl.UpdateThread.run(UpdateThread.java:88)

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Re: @Requires : ServiceFactory.getService() resulted in a cycle.

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