[FELIX-1841] SCR invokes bind method twice when dependency service properties are modified

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: scr-1.2.0
• Fix Version/s: scr-1.4.0
• Component/s: Declarative Services (SCR)
• Assignee: Felix Meschberger
• Reporter: Pierre De Rop
• Created: 03/Nov/09 12:45
• Updated: 30/Jul/10 11:42
• Resolved: 26/Nov/09 07:27

Description

It seems that when a service S is depending on another service D, and when D service properties are modified (using ServiceRegistration.setProperties method), then D is
re-bound twice into the using service S.

For example, I have a service "Client" has a "1..1" dependency over "Service":

<?xml version="1.0" encoding="UTF-8"?>
<component name="Client">
<implementation class="client.Client"/>
<reference name="SERVICE"
interface="service.Service"
policy="dynamic"
cardinality="1..1"
target="(foo=bar)"
bind="bind"/>
</component>

public class Client {
protected void bind(Service s)

{ System.out.println("Client:: bound Service : " + s); Thread.dumpStack(); }

}

I have another bundle which provide the "Service" dependency, and sometimes, the "Service" properties are modified like this:

ServiceRegistration reg ...
reg.setProperties(...)

So, when the setProperties takes place, "Client" is re-bound twice with the service "Service".
Indeed, in DependencyManager, when a ServiceEvent.MODIFIED event. is caught, the following code is invoked (line 170):

case ServiceEvent.MODIFIED:
m_componentManager.log( LogService.LOG_DEBUG, "Dependency Manager: Updating

{0}

", new Object[]

{ serviceString }

, null );

// remove the service first
// only continue with further event handling if the service
// removal did not cause the component to be deactivated
if ( serviceRemoved( ref ) )
{
// recalculate the number of services matching the filter
// because we don't know whether this service previously matched
// or not
ServiceReference refs[] = getFrameworkServiceReferences();
m_size = ( refs == null ) ? 0 : refs.length;

// now try to bind the service - if it matches the target filter
// without recalculating the size (already done).
if ( targetFilterMatch( ref ) )

{ serviceAdded( ref ); }

}

break;

So, the service is first re-bound to the Client, when the serviceRemoved() method is invoked (it's a bound service replacement, I guess).
But the problem here is that the modified service is also re-bound, when serviceAdded is invoked (line 189).
Don't you think that this is a bug and the service should be re-bound only once, not twice ?

Here is the first stacktrace of the first bind:

java.lang.Exception: Stack trace
at java.lang.Thread.dumpStack(Thread.java:1158)
at client.Client.bind(Client.java:13)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:592)
at org.apache.felix.scr.impl.helper.BaseMethod.invokeMethod(BaseMethod.java:213)
at org.apache.felix.scr.impl.helper.BaseMethod.access$500(BaseMethod.java:38)
at org.apache.felix.scr.impl.helper.BaseMethod$Resolved.invoke(BaseMethod.java:542)
at org.apache.felix.scr.impl.helper.BaseMethod.invoke(BaseMethod.java:434)
at org.apache.felix.scr.impl.manager.DependencyManager.invokeBindMethod(DependencyManager.java:948)
at org.apache.felix.scr.impl.manager.DependencyManager.bind(DependencyManager.java:884)
at org.apache.felix.scr.impl.manager.DependencyManager.serviceRemoved(DependencyManager.java:367)
at org.apache.felix.scr.impl.manager.DependencyManager.serviceChanged(DependencyManager.java:177)
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:3587)
at org.apache.felix.framework.Felix.access$000(Felix.java:40)
at org.apache.felix.framework.Felix$1.serviceChanged(Felix.java:625)
at org.apache.felix.framework.ServiceRegistry.servicePropertiesModified(ServiceRegistry.java:505)
at org.apache.felix.framework.ServiceRegistrationImpl.setProperties(ServiceRegistrationImpl.java:116)
at service.impl.ServiceFactory.run(ServiceFactory.java:48)
at java.lang.Thread.run(Thread.java:595)

and here is the second stacktrace, when Service is re-bound:

Client: bound Service : service.impl.ServiceImpl@142a80d
java.lang.Exception: Stack trace
at java.lang.Thread.dumpStack(Thread.java:1158)
at client.Client.bind(Client.java:13)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:592)
at org.apache.felix.scr.impl.helper.BaseMethod.invokeMethod(BaseMethod.java:213)
at org.apache.felix.scr.impl.helper.BaseMethod.access$500(BaseMethod.java:38)
at org.apache.felix.scr.impl.helper.BaseMethod$Resolved.invoke(BaseMethod.java:542)
at org.apache.felix.scr.impl.helper.BaseMethod.invoke(BaseMethod.java:434)
at org.apache.felix.scr.impl.manager.DependencyManager.invokeBindMethod(DependencyManager.java:948)
at org.apache.felix.scr.impl.manager.DependencyManager.serviceAdded(DependencyManager.java:271)
at org.apache.felix.scr.impl.manager.DependencyManager.serviceChanged(DependencyManager.java:189)
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:3587)
at org.apache.felix.framework.Felix.access$000(Felix.java:40)
at org.apache.felix.framework.Felix$1.serviceChanged(Felix.java:625)
at org.apache.felix.framework.ServiceRegistry.servicePropertiesModified(ServiceRegistry.java:505)
at org.apache.felix.framework.ServiceRegistrationImpl.setProperties(ServiceRegistrationImpl.java:116)
at service.impl.ServiceFactory.run(ServiceFactory.java:48)
at java.lang.Thread.run(Thread.java:595)

Issue Links

• relates to: FELIX-1866 SCR 1.1 restarts components when service properties are changed, even if "modified" attributed is specified