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https://issues.apache.org/jira/browse/FELIX-4984?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14693635#comment-14693635
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David Jencks commented on FELIX-4984:
-------------------------------------
After studying this for a while I think that what is happening is that we're
remembering to "bind later" a reference for a component that can't possibly be
created from the original request, because of cardinality constraints. Then
when it _is_ created (due to starting at a different point in the cycle) the
leftover "bind later" request is binding the same object as the "normally
working" bind, but to a different object than we originally expected. I'm not
entirely sure why this only happens occasionally.
I have a proposal (see patch) to only add a "bind later" request when the
cardinality is otherwise satisfied, without the missing dependency, so that if
we know the component can't be created we don't add the "bind later" request.
Do you think this is at least on the right track? It now occurs to me that
perhaps checking _all_ the references before adding any "bind later" requests
would be safer.
> Issues in CircularReferenceTest
> -------------------------------
>
> Key: FELIX-4984
> URL: https://issues.apache.org/jira/browse/FELIX-4984
> Project: Felix
> Issue Type: Bug
> Components: Declarative Services (SCR)
> Reporter: Pierre De Rop
> Priority: Minor
> Attachments:
> org.apache.felix.scr.integration.CircularReferenceTest.test_A11_B0n_delayed_B_first.log
>
>
> This issue is described in the dev mailing list, in
> http://www.mail-archive.com/[email protected]/msg37281.html
> while working on FELIX-4955, I sometimes have the CircularReferenceTest
> failing.
> Everything is located in my sandbox, in
> http://svn.apache.org/repos/asf/felix/sandbox/pderop/dependencymanager.ds/
> To reproduce the test:
> install eclipse Mars
> install latest bndtools using "install new software" from Eclipse, and then
> add latest stable release from http://dl.bintray.com/bndtools/bndtools/latest/
> install a java8 runtime (I'm using oracle java8 1.8.0_45, 64 bit version).
> The whole new dependencymanager.ds project is intented to be build in java8.
> checkout my sandbox:
> $ svn checkout
> http://svn.apache.org/repos/asf/felix/sandbox/pderop/dependencymanager.ds
> go to "dependencymanager.ds" directory:
> $ cd dependencymanager.ds/
> due to a pending issue, you have to first build the DM bnd annotation plugin
> before importing the project into eclipse. to do so, just type:
> $ ./gradlew org.apache.felix.dependencymanager.annotation:jar
> now launch eclipse and use the the dependencymanager/ds directory as the
> workspace dir for Eclipse.
> switch to BndTools perpective.
> import the bndtools project into eclipse: Import -> Existing Projects into
> Workspace -> Browse -> select dependencymanager.ds directory (it is proposed
> by default).
> normally, and hopefully, everything should compile fine. Junit tests are left
> in org.apache.felix.dependencymanager.ds/ directory and integration tests are
> located in org.apache.felix.dependencymanager.ds.itest/ directory.
> Open under Eclipse the
> org.apache.felix.dependencymanager.ds.itest/src/org/apache/felix/scr/integration/CircularReferenceTest.java
> I slightly modified it in order to dump stack traces when A component is
> bound multiple times to the same B instance.
> (I believe that only delayed components are concerned by the issue).
> For example, in the test_A11_B0n_delayed_A_first() method, I added a call to
> "assertABoundToOneB(a)" like this:
> {code}
> @Test
> public void test_A11_B0n_delayed_A_first() throws InvalidSyntaxException
> {
> String componentNameA = "4.1.A.1.1.dynamic";
> final ComponentConfigurationDTO componentA =
> findComponentConfigurationByName( componentNameA,
> ComponentConfigurationDTO.SATISFIED );
> String componentNameB = "4.1.B.0.n.dynamic";
> final ComponentConfigurationDTO componentB =
> findComponentConfigurationByName( componentNameB,
> ComponentConfigurationDTO.SATISFIED );
> delay();
> A a = getServiceFromConfiguration(componentA, A.class);
> assertABoundToOneB(a);
> delay(); //async binding of a to b after circular ref detected
> B b = getServiceFromConfiguration(componentB, B.class);
> assertEquals( 1, b.getAs().size() );
> }
> {code}
> the "assertABoundToOneB(a)" call does this:
> {code}
> private void assertABoundToOneB(A a) {
> if (a.getBs().size() != 1) {
> System.err.println("detected problem ...");
> a.dumpStackTracesWhenBWasBound();
> }
> assertEquals( 1, a.getBs().size());
> }
> {code}
> And stacktraces will be dumped in order to determine why A was bound two
> times to the same B instance.
> it's possible that you have to run several times the "CircularReferenceTest"
> test before having a failure (and some stacktraces).
> Thanks.
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