[FELIX-4854] Unable to create consistent wiring when same package is exported in same version by multiple bundles

• Type: Bug
• Status: Closed
• Priority: Critical
• Resolution: Not A Problem
• Affects Version/s: framework-4.6.1
• Fix Version/s: framework-5.0.0
• Component/s: Framework
• Labels: framework resolution wiring
• Assignee: Unassigned
• Reporter: Jens Offenbach
• Created: 16/Apr/15 09:35
• Updated: 17/Apr/15 04:30
• Resolved: 17/Apr/15 04:30

Description

I am confronted with a strange wiring problem in Felix. Actually I am not sure if this is a problem in the Felix or Equinox framework. The attached test case shows that there is a differen behaviour in the wiring process between Felix 4.6.1 and Equinox 3.10.2.v20150203-1939 when we have different bundles with different versions exporting the same package in the same version:

The OSGi specification says:
The following list defines the preferences, if multiple choices are possible, in order of decreasing priority:
• A resolved exporter must be preferred over an unresolved exporter.
• An exporter with a higher version is preferred over an exporter with a lower version.
• An exporter with a lower bundle ID is preferred over a bundle with a higher ID.

Let us assume that we have BundleA:1.0.0 and BundleB:2.0.0 both exporting the same package in the same version and we have SampleA and SampleB importing the package. BundleA gets installed and started, then SampleA. I think SampleA gets wired to BundleA:1.0.0. Now BundleB:2.0.0 gets installed and started, followed by SampleB. To which bundle must SampleB be wired? Strict to the OSGi specification, I would say to BundleB:2.0.0, because it has a higher version than BundleA because BundleA and BundleB are both resolved. But does it make sense? I think BundleA:1.0.0 should be preferred because it is already an active part of the resolution process, but I cannot find anything in the specification.

Can someone please explain me, what is going on in the attached use case. Why do we get a different wiring result in Felix 4.6.1 and Equinox 3.10.2.v20150203-1939.

The attached demo use case can be executed via:

mvn clean install -Pfelix
mvn clean install -Pequinox

Felix 4.6.1:

testWiringA()
org.apache.felix.osgi.r6.wiring.sampleA uses org.apache.felix.osgi.r6.wiring.bundleA:1.0.0
org.apache.felix.osgi.r6.wiring.sampleB uses org.apache.felix.osgi.r6.wiring.bundleB:2.0.0

testWiringB()
org.apache.felix.osgi.r6.wiring.sampleA uses org.apache.felix.osgi.r6.wiring.bundleA:1.0.0
org.apache.felix.osgi.r6.wiring.sampleB uses org.apache.felix.osgi.r6.wiring.bundleA:1.0.0

Equinox 3.10.2.v20150203-1939:

testWiringA()
org.apache.felix.osgi.r6.wiring.sampleA uses org.apache.felix.osgi.r6.wiring.bundleB:2.0.0
org.apache.felix.osgi.r6.wiring.sampleB uses org.apache.felix.osgi.r6.wiring.bundleB:2.0.0

testWiringB()
org.apache.felix.osgi.r6.wiring.sampleA uses org.apache.felix.osgi.r6.wiring.bundleA:1.0.0
org.apache.felix.osgi.r6.wiring.sampleB uses org.apache.felix.osgi.r6.wiring.bundleA:1.0.0

The use case is derived from a bigger one resulting in a problematic wiring when the OSGi Compendium is installed in version 4.3.1 and version 5.0.0 in combination with Felix SCR 1.8.2. In my productive scenario, Felix 4.6.1 wires my bundles to OSGi Compendium:4.3.1 and Felix SCR to OSGi Compendium:5.0.0. In this case Felix SCR gets into trouble during introspection, because (based on that wiring) SCR cannot find the activate method when it has the ComponentContext class in its signature. Both ComponentContext classes are not equal, because they are provided by different classloaders.