Circular task dependency to 'self' is hard to diagnose

stefk · December 20, 2011, 12:09am

i.e. in milestone 3 the project builds fine, but when upgrading to m5 (or m6) the build stops with:

* Exception is:
16:06:21.824 [ERROR] [org.gradle.BuildExceptionReporter] org.gradle.api.CircularReferenceException: Circular dependency between tasks. Cycle includes [task ':<...>:cmdline', task ':<...>:cmdline'].
16:06:21.824 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.execution.DefaultTaskGraphExecuter.fillDag(DefaultTaskGraphExecuter.java:121)
16:06:21.824 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.execution.DefaultTaskGraphExecuter.addTasks(DefaultTaskGraphExecuter.java:71)
16:06:21.824 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.execution.TaskNameResolvingBuildConfigurationAction.configure(TaskNameResolvingBuildConfigurationAction.java:57)
16:06:21.825 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.execution.DefaultBuildExecuter.configure(DefaultBuildExecuter.java:43)
16:06:21.825 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.execution.DefaultBuildExecuter.access$200(DefaultBuildExecuter.java:23)
16:06:21.825 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.execution.DefaultBuildExecuter$1.proceed(DefaultBuildExecuter.java:53)
16:06:21.825 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.execution.ExcludedTaskFilteringBuildConfigurationAction.configure(ExcludedTaskFilteringBuildConfigurationAction.java:55)
16:06:21.825 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.execution.DefaultBuildExecuter.configure(DefaultBuildExecuter.java:43)
16:06:21.825 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.execution.DefaultBuildExecuter.access$200(DefaultBuildExecuter.java:23)
16:06:21.826 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.execution.DefaultBuildExecuter$1.proceed(DefaultBuildExecuter.java:53)
16:06:21.826 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.execution.DefaultTasksBuildExecutionAction.configure(DefaultTasksBuildExecutionAction.java:34)
16:06:21.826 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.execution.DefaultBuildExecuter.configure(DefaultBuildExecuter.java:43)
16:06:21.826 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.execution.DefaultBuildExecuter.select(DefaultBuildExecuter.java:36)
16:06:21.826 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.initialization.DefaultGradleLauncher.doBuildStages(DefaultGradleLauncher.java:149)
16:06:21.826 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.initialization.DefaultGradleLauncher.doBuild(DefaultGradleLauncher.java:112)
16:06:21.826 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.initialization.DefaultGradleLauncher.run(DefaultGradleLauncher.java:80)
16:06:21.827 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.launcher.cli.RunBuildAction.execute(RunBuildAction.java:42)
16:06:21.827 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.launcher.cli.RunBuildAction.execute(RunBuildAction.java:28)
16:06:21.827 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.launcher.exec.ExceptionReportingAction.execute(ExceptionReportingAction.java:32)
16:06:21.827 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.launcher.exec.ExceptionReportingAction.execute(ExceptionReportingAction.java:21)
16:06:21.827 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.launcher.cli.CommandLineActionFactory$WithLoggingAction.execute(CommandLineActionFactory.java:233)
16:06:21.827 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.launcher.cli.CommandLineActionFactory$WithLoggingAction.execute(CommandLineActionFactory.java:217)
16:06:21.827 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.launcher.Main.doAction(Main.java:48)
16:06:21.828 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.launcher.exec.EntryPoint$1.execute(EntryPoint.java:53)
16:06:21.828 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.launcher.exec.EntryPoint$1.execute(EntryPoint.java:51)
16:06:21.828 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.launcher.exec.Execution.execute(Execution.java:28)
16:06:21.828 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.launcher.exec.EntryPoint.run(EntryPoint.java:39)
16:06:21.828 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.launcher.Main.main(Main.java:39)
16:06:21.828 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.launcher.ProcessBootstrap.runNoExit(ProcessBootstrap.java:51)
16:06:21.828 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.launcher.ProcessBootstrap.run(ProcessBootstrap.java:33)
16:06:21.829 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.launcher.GradleMain.main(GradleMain.java:24)

Incidentally the task is somehow circularly dependent on itself?

Any ideas appreciated.

Szczepan_Faber · December 20, 2011, 1:53pm

Hey Stefan,

It looks like the problem occurs regardless of the tasks you run. Can you confirm?

stefk · December 20, 2011, 4:35pm

Yes, actually running gradle tasks gives me a java.util.ConcurrentModificationException:

08:34:15.504 [DEBUG] [org.gradle.api.internal.tasks.execution.SkipUpToDateTaskExecuter] task ':tasks' is not up-to-date
08:34:15.505 [DEBUG] [org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter] Executing actions for task ':tasks'.
08:34:15.506 [QUIET] [org.gradle.api.tasks.diagnostics.TaskReportTask_Decorated]
 08:34:15.506 [QUIET] [org.gradle.api.tasks.diagnostics.TaskReportTask_Decorated] ------------------------------------------------------------
08:34:15.507 [QUIET] [org.gradle.api.tasks.diagnostics.TaskReportTask_Decorated] All tasks runnable from root project
08:34:15.507 [QUIET] [org.gradle.api.tasks.diagnostics.TaskReportTask_Decorated] ------------------------------------------------------------
08:34:15.508 [QUIET] [org.gradle.api.tasks.diagnostics.TaskReportTask_Decorated]
 08:34:15.703 [DEBUG] [org.gradle.api.internal.tasks.execution.ExecuteAtMostOnceTaskExecuter] Finished executing task ':tasks'
08:34:15.706 [ERROR] [org.gradle.BuildExceptionReporter]
 08:34:15.707 [ERROR] [org.gradle.BuildExceptionReporter] FAILURE: Build failed with an exception.
08:34:15.707 [ERROR] [org.gradle.BuildExceptionReporter]
 08:34:15.707 [ERROR] [org.gradle.BuildExceptionReporter] * What went wrong:
08:34:15.708 [ERROR] [org.gradle.BuildExceptionReporter] Execution failed for task ':tasks'.
08:34:15.709 [ERROR] [org.gradle.BuildExceptionReporter] Cause: java.util.ConcurrentModificationException (no error message)
08:34:15.709 [ERROR] [org.gradle.BuildExceptionReporter]
 08:34:15.710 [ERROR] [org.gradle.BuildExceptionReporter] * Exception is:
08:34:15.710 [ERROR] [org.gradle.BuildExceptionReporter] org.gradle.api.tasks.TaskExecutionException: Execution failed for task ':tasks'.
08:34:15.710 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:71)
08:34:15.710 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.execute(ExecuteActionsTaskExecuter.java:48)
08:34:15.711 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.api.internal.tasks.execution.PostExecutionAnalysisTaskExecuter.execute(PostExecutionAnalysisTaskExecuter.java:34)
08:34:15.711 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.api.internal.tasks.execution.SkipUpToDateTaskExecuter.execute(SkipUpToDateTaskExecuter.java:55)
08:34:15.711 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.api.internal.tasks.execution.ValidatingTaskExecuter.execute(ValidatingTaskExecuter.java:57)
08:34:15.711 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.api.internal.tasks.execution.SkipEmptySourceFilesTaskExecuter.execute(SkipEmptySourceFilesTaskExecuter.java:41)
08:34:15.711 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.api.internal.tasks.execution.SkipTaskWithNoActionsExecuter.execute(SkipTaskWithNoActionsExecuter.java:51)
08:34:15.711 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.api.internal.tasks.execution.SkipOnlyIfTaskExecuter.execute(SkipOnlyIfTaskExecuter.java:52)
08:34:15.712 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.api.internal.tasks.execution.ExecuteAtMostOnceTaskExecuter.execute(ExecuteAtMostOnceTaskExecuter.java:42)
08:34:15.712 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.api.internal.AbstractTask.executeWithoutThrowingTaskFailure(AbstractTask.java:243)
08:34:15.712 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.execution.DefaultTaskGraphExecuter.executeTask(DefaultTaskGraphExecuter.java:192)
08:34:15.712 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.execution.DefaultTaskGraphExecuter.doExecute(DefaultTaskGraphExecuter.java:177)
08:34:15.712 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.execution.DefaultTaskGraphExecuter.execute(DefaultTaskGraphExecuter.java:83)
08:34:15.713 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.execution.SelectedTaskExecutionAction.execute(SelectedTaskExecutionAction.java:36)
08:34:15.713 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:70)
08:34:15.713 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.execution.DefaultBuildExecuter.access$300(DefaultBuildExecuter.java:23)
08:34:15.713 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.execution.DefaultBuildExecuter$2.proceed(DefaultBuildExecuter.java:80)
08:34:15.713 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.execution.DryRunBuildExecutionAction.execute(DryRunBuildExecutionAction.java:32)
08:34:15.713 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:70)
08:34:15.714 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:63)
08:34:15.714 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.initialization.DefaultGradleLauncher.doBuildStages(DefaultGradleLauncher.java:157)
08:34:15.714 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.initialization.DefaultGradleLauncher.doBuild(DefaultGradleLauncher.java:112)
08:34:15.714 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.initialization.DefaultGradleLauncher.run(DefaultGradleLauncher.java:80)
08:34:15.714 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.launcher.cli.RunBuildAction.execute(RunBuildAction.java:42)
08:34:15.714 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.launcher.cli.RunBuildAction.execute(RunBuildAction.java:28)
08:34:15.715 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.launcher.exec.ExceptionReportingAction.execute(ExceptionReportingAction.java:32)
08:34:15.715 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.launcher.exec.ExceptionReportingAction.execute(ExceptionReportingAction.java:21)
08:34:15.715 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.launcher.cli.CommandLineActionFactory$WithLoggingAction.execute(CommandLineActionFactory.java:233)
08:34:15.715 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.launcher.cli.CommandLineActionFactory$WithLoggingAction.execute(CommandLineActionFactory.java:217)
08:34:15.715 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.launcher.Main.doAction(Main.java:48)
08:34:15.715 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.launcher.exec.EntryPoint$1.execute(EntryPoint.java:53)
08:34:15.716 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.launcher.exec.EntryPoint$1.execute(EntryPoint.java:51)
08:34:15.716 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.launcher.exec.Execution.execute(Execution.java:28)
08:34:15.716 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.launcher.exec.EntryPoint.run(EntryPoint.java:39)
08:34:15.716 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.launcher.Main.main(Main.java:39)
08:34:15.716 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.launcher.ProcessBootstrap.runNoExit(ProcessBootstrap.java:51)
08:34:15.717 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.launcher.ProcessBootstrap.run(ProcessBootstrap.java:33)
08:34:15.717 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.launcher.GradleMain.main(GradleMain.java:24)
08:34:15.717 [ERROR] [org.gradle.BuildExceptionReporter] Caused by: java.util.ConcurrentModificationException
08:34:15.717 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.api.internal.DefaultDomainObjectCollection$IteratorImpl.next(DefaultDomainObjectCollection.java:313)
08:34:15.717 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.api.internal.GraphAggregator.group(GraphAggregator.java:33)
08:34:15.717 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.api.tasks.diagnostics.internal.SingleProjectTaskReportModel.build(SingleProjectTaskReportModel.java:61)
08:34:15.718 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.api.tasks.diagnostics.TaskReportTask.generate(TaskReportTask.java:67)
08:34:15.718 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.api.tasks.diagnostics.AbstractReportTask.generate(AbstractReportTask.java:67)
08:34:15.718 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.api.internal.BeanDynamicObject.invokeMethod(BeanDynamicObject.java:158)
08:34:15.718 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.api.internal.CompositeDynamicObject.invokeMethod(CompositeDynamicObject.java:93)
08:34:15.718 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.api.tasks.diagnostics.TaskReportTask_Decorated.invokeMethod(Unknown Source)
08:34:15.718 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.util.ReflectionUtil.invoke(ReflectionUtil.groovy:23)
08:34:15.719 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$2.execute(AnnotationProcessingTaskFactory.java:129)
08:34:15.719 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$2.execute(AnnotationProcessingTaskFactory.java:127)
08:34:15.719 [ERROR] [org.gradle.BuildExceptionReporter]
at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:63)
08:34:15.719 [ERROR] [org.gradle.BuildExceptionReporter]
... 37 more

The other tasks I tried are:

test

:

gave circular task error

dependency

:

worked fine

clean

: worked fine

build

: gave circular task error

stefk · December 22, 2011, 8:18am

I can add that milestone-6 has exactly the same issues.

Peter_Niederwieser · December 22, 2011, 4:00pm

Can you provide a build that allows us to reproduce the problem(s)?

stefk · December 22, 2011, 4:26pm

Sure, I’ll see what I can do.

stefk · December 22, 2011, 6:54pm

Um, I’m not exactly sure what’s the easiest way to do this, however through using the debugger I have managed to find the case where the “tasks” task breaks:

Inside GraphAggregator.java there is this method:

public Result<N> group(Collection<? extends N> startNodes, Collection<? extends N> allNodes) {
        Map<N, Set<N>> reachableByNode = new HashMap<N, Set<N>>();
        Set<N> topLevelNodes = new LinkedHashSet<N>(allNodes);
        for (N node : allNodes) {
            Set<N> reachableNodes = graphWalker.add(node).findValues();
            reachableByNode.put(node, reachableNodes);
            topLevelNodes.removeAll(reachableNodes);
        }
        topLevelNodes.addAll(startNodes);
        Map<N, Set<N>> nodes = new HashMap<N, Set<N>>();
        for (N node : topLevelNodes) {
            nodes.put(node, calculateReachableNodes(reachableByNode, node, topLevelNodes));
        }
        return new Result<N>(nodes, topLevelNodes);
    }

The ConcurrentModificationException is thrown on one of the

topLevelNodes.removeAll(reachableNodes);

calls (Note: since gradle is single threaded, so the only way this exception would be thrown is by modifying some iterator while we are iterating).

Let me setup all the variables which lead to the exception being thrown: allNodes is the following

[task ':databus-bootstrap-client:databus-bootstrap-client-impl:assemble', task ':databus-bootstrap-client:databus-bootstrap-client-impl:build', task ':databus-bootstrap-client:databus-bootstrap-client-impl:buildDependents', task ':databus-bootstrap-client:databus-bootstrap-client-impl:buildNeeded', task ':databus-bootstrap-client:databus-bootstrap-client-impl:check', task ':databus-bootstrap-client:databus-bootstrap-client-impl:classes', task ':databus-bootstrap-client:databus-bootstrap-client-impl:clean', task ':databus-bootstrap-client:databus-bootstrap-client-impl:cleanEclipse', task ':databus-bootstrap-client:databus-bootstrap-client-impl:cleanEclipseClasspath', task ':databus-bootstrap-client:databus-bootstrap-client-impl:cleanEclipseJdt', task ':databus-bootstrap-client:databus-bootstrap-client-impl:cleanEclipseProject', task ':databus-bootstrap-client:databus-bootstrap-client-impl:cleanIdea', task ':databus-bootstrap-client:databus-bootstrap-client-impl:cleanIdeaModule', task ':databus-bootstrap-client:databus-bootstrap-client-impl:cleanTest', task ':databus-bootstrap-client:databus-bootstrap-client-impl:cobertura', task ':databus-bootstrap-client:databus-bootstrap-client-impl:coberturaXml', task ':databus-bootstrap-client:databus-bootstrap-client-impl:compileJava', task ':databus-bootstrap-client:databus-bootstrap-client-impl:compileTestJava', task ':databus-bootstrap-client:databus-bootstrap-client-impl:dependencyReport', task ':databus-bootstrap-client:databus-bootstrap-client-impl:eclipse', task ':databus-bootstrap-client:databus-bootstrap-client-impl:eclipseClasspath', task ':databus-bootstrap-client:databus-bootstrap-client-impl:eclipseJdt', task ':databus-bootstrap-client:databus-bootstrap-client-impl:eclipseProject', task ':databus-bootstrap-client:databus-bootstrap-client-impl:findbugs', task ':databus-bootstrap-client:databus-bootstrap-client-impl:findbugs-text', task ':databus-bootstrap-client:databus-bootstrap-client-impl:idea', task ':databus-bootstrap-client:databus-bootstrap-client-impl:ideaModule', task ':databus-bootstrap-client:databus-bootstrap-client-impl:instrumentedJar', task ':databus-bootstrap-client:databus-bootstrap-client-impl:ivyForArchives', task ':databus-bootstrap-client:databus-bootstrap-client-impl:jar', task ':databus-bootstrap-client:databus-bootstrap-client-impl:javadoc', task ':databus-bootstrap-client:databus-bootstrap-client-impl:javadocJar', task ':databus-bootstrap-client:databus-bootstrap-client-impl:processResources', task ':databus-bootstrap-client:databus-bootstrap-client-impl:processTestResources', task ':databus-bootstrap-client:databus-bootstrap-client-impl:projectReport', task ':databus-bootstrap-client:databus-bootstrap-client-impl:propertyReport', task ':databus-bootstrap-client:databus-bootstrap-client-impl:release', task ':databus-bootstrap-client:databus-bootstrap-client-impl:sourcesJar', task ':databus-bootstrap-client:databus-bootstrap-client-impl:taskReport', task ':databus-bootstrap-client:databus-bootstrap-client-impl:test', task ':databus-bootstrap-client:databus-bootstrap-client-impl:testClasses', task ':databus-bootstrap-client:databus-bootstrap-client-impl:upload', task ':databus-bootstrap-client:databus-bootstrap-client-impl:uploadArchives', task ':databus-bootstrap-client:databus-bootstrap-client-impl:uploadDefault', task ':databus-bootstrap-client:databus-bootstrap-client-impl:uploadDocs', task ':databus-bootstrap-client:databus-bootstrap-client-impl:uploadJavadoc', task ':databus-bootstrap-client:databus-bootstrap-client-impl:uploadRuntime', task ':databus-bootstrap-client:databus-bootstrap-client-impl:uploadSources', task ':databus-bootstrap-client:databus-bootstrap-client-impl:uploadTestRuntime']

We can assume that the for loop iterates over the allNodes in the sequence provided.
Skipping ahead to the point where the

N node = task ':databus-bootstrap-client:databus-bootstrap-client-impl:cobertura'

we have the following

reachableNodes = [task ':databus-bootstrap-client:databus-bootstrap-client-impl:instrumentedJar', task ':databus-bootstrap-client:databus-bootstrap-client-impl:coberturaXml', task ':databus-bootstrap-client:databus-bootstrap-client-impl:cleanTest', task ':databus-bootstrap-client:databus-bootstrap-client-impl:test', task ':databus-bootstrap-client:databus-bootstrap-client-impl:testClasses', task ':databus-bootstrap-client:databus-bootstrap-client-impl:classes', task ':databus-bootstrap-client:databus-bootstrap-client-impl:processTestResources', task ':databus-bootstrap-client:databus-bootstrap-client-impl:compileTestJava', task ':databus-bootstrap-client:databus-bootstrap-client-impl:compileJava', task ':databus-bootstrap-client:databus-bootstrap-client-impl:processResources']

and the state of the topLevelNodes just before removeAll is called with the reachableNodes set above is :

topLevelNodes = [task ':databus-bootstrap-client:databus-bootstrap-client-impl:buildDependents', task ':databus-bootstrap-client:databus-bootstrap-client-impl:buildNeeded', task ':databus-bootstrap-client:databus-bootstrap-client-impl:clean', task ':databus-bootstrap-client:databus-bootstrap-client-impl:cleanEclipse', task ':databus-bootstrap-client:databus-bootstrap-client-impl:cleanIdea', task ':databus-bootstrap-client:databus-bootstrap-client-impl:cobertura', task ':databus-bootstrap-client:databus-bootstrap-client-impl:coberturaXml', task ':databus-bootstrap-client:databus-bootstrap-client-impl:dependencyReport', task ':databus-bootstrap-client:databus-bootstrap-client-impl:eclipse', task ':databus-bootstrap-client:databus-bootstrap-client-impl:eclipseClasspath', task ':databus-bootstrap-client:databus-bootstrap-client-impl:eclipseJdt', task ':databus-bootstrap-client:databus-bootstrap-client-impl:eclipseProject', task ':databus-bootstrap-client:databus-bootstrap-client-impl:findbugs', task ':databus-bootstrap-client:databus-bootstrap-client-impl:findbugs-text', task ':databus-bootstrap-client:databus-bootstrap-client-impl:idea', task ':databus-bootstrap-client:databus-bootstrap-client-impl:ideaModule', task ':databus-bootstrap-client:databus-bootstrap-client-impl:ivyForArchives', task ':databus-bootstrap-client:databus-bootstrap-client-impl:javadoc', task ':databus-bootstrap-client:databus-bootstrap-client-impl:javadocJar', task ':databus-bootstrap-client:databus-bootstrap-client-impl:projectReport', task ':databus-bootstrap-client:databus-bootstrap-client-impl:propertyReport', task ':databus-bootstrap-client:databus-bootstrap-client-impl:release', task ':databus-bootstrap-client:databus-bootstrap-client-impl:sourcesJar', task ':databus-bootstrap-client:databus-bootstrap-client-impl:taskReport', task ':databus-bootstrap-client:databus-bootstrap-client-impl:upload', task ':databus-bootstrap-client:databus-bootstrap-client-impl:uploadArchives', task ':databus-bootstrap-client:databus-bootstrap-client-impl:uploadDefault', task ':databus-bootstrap-client:databus-bootstrap-client-impl:uploadDocs', task ':databus-bootstrap-client:databus-bootstrap-client-impl:uploadJavadoc', task ':databus-bootstrap-client:databus-bootstrap-client-impl:uploadRuntime', task ':databus-bootstrap-client:databus-bootstrap-client-impl:uploadSources', task ':databus-bootstrap-client:databus-bootstrap-client-impl:uploadTestRuntime']

So examining the reachableNodes, topLevelNodes & allNodes variables, we see that the next value of N node would be :databus-bootstrap-client:databus-bootstrap-client-impl:coberturaXml. But it is also in reachableNodes and topLevelNodes. So when we come to do a removeAll on topLevelNodes, we expect :databus-bootstrap-client:databus-bootstrap-client-impl:coberturaXml to be removed. However the way topLevelNodes is initialized, it causes some deeper iterator interference which modifies the iterator being used for the for loop and thus the exception :(.
Please advise.

daz · December 22, 2011, 7:24pm

Thanks for the detailed analysis. It will certainly help us in our investigation.

stefk · December 22, 2011, 9:18pm

One minor correction: the exception is thrown by the for loop when it does to get the next item, not in the removeAll step. i.e. after the removeAll step and we go to the next iteration of the forloop (which does a iterator.next() call).

Szczepan_Faber · January 4, 2012, 12:38am

Hey Stefan,

By reading the code I cannot figure out how come that exception can be thrown. topLevelNodes, reachableNodes can contain the same item and we still should be able to removeAll() without interfering.

Do you have that dev environment still set up? Can we pair on it remotely? If we cannot than I suggest to dig a bit into what is changed in the allNodes and when (e.g. eager breakpoint at all mutators or some more code analysis)

Szczepan_Faber · January 4, 2012, 5:02pm

The issue has been solved by removing the circular dependency. However, the problem with awkward reporting still persists, e.g. “Cycle includes [task ‘:<…>:cmdline’, task ‘:<…>:cmdline’]”.

I’ll push that to jira.

stefk · January 5, 2012, 5:07am

Well it’s the next thing that the for loop iterator would go over, and it’s just been removed… But yeah I havent had a chance to debug it with the fix to see what’s changed.

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Circular task dependency to 'self' is hard to diagnose

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