[Umbrella Issue] Many tests use Thread.sleep instead of synchronization primitives

Many of our tests simply have a Thread.sleep(duration) when testing multi-threaded code. This is inherently flaky.

Instead we should use synchronization classes (generally Semaphore) to synchronized the tests which is both faster in the general case and not flaky in the extreme case.

See for instance #1218 and #1219

util/src/test/java/io/kubernetes/client/informer/cache/ReflectorRunnableTest.java
extended/src/test/java/io/kubernetes/client/extended/workqueue/DefaultDelayingQueueTest.java
util/src/test/java/io/kubernetes/client/informer/cache/ProcessorListenerTest.java
util/src/test/java/io/kubernetes/client/informer/cache/SharedProcessorTest.java
util/src/test/java/io/kubernetes/client/CopyTest.java
util/src/test/java/io/kubernetes/client/informer/cache/ControllerTest.java
extended/src/test/java/io/kubernetes/client/extended/workqueue/DefaultWorkQueueTest.java
extended/src/test/java/io/kubernetes/client/extended/leaderelection/LeaderElectionTest.java
util/src/test/java/io/kubernetes/client/informer/impl/DefaultSharedIndexInformerTest.java
extended/src/test/java/io/kubernetes/client/extended/controller/LeaderElectingControllerTest.java
util/src/test/java/io/kubernetes/client/PortForwardTest.java
util/src/test/java/io/kubernetes/client/AttachTest.java
util/src/test/java/io/kubernetes/client/ExecTest.java
extended/src/test/java/io/kubernetes/client/extended/workqueue/ratelimiter/BucketRateLimiterTest.java
spring/src/test/java/io/kubernetes/client/spring/extended/controller/KubernetesInformerCreatorTest.java
spring/src/test/java/io/kubernetes/client/spring/extended/controller/KubernetesReconcilerCreatorTest.java
extended/src/test/java/io/kubernetes/client/extended/event/EventCorrelatorTest.java

@brendandburns

@brendandburns thanks for sorting out these potentially flaking tests.. will fix them later!

/assign

I would like to help :-)

@sarveshkaushal

@sarveshkaushal we'd welcome the help. In most cases the Thread.sleep(foo) is to wait for some other thread to complete it's work. Instead, we should create a Semaphore, then acquire() one or more permits for the executions we're waiting for, and then release() them in the Thread, then attempt to acquire() in the test thread to implement the wait.

See an example PR #1219

The reason that Thread.sleep() is flaky is because in a CI/CD system like GitHub actions the machines can be massively overloaded, which leads to much longer delays than you might otherwise see when running tests, so the sleep(..) ends up not being long enough. You can always make the sleep longer, but that makes the tests run longer (and it's still flaky in extreme cases) so using synchronization primitives is (almost) always the right answer.

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If still available I would like to contribute

@brendandburns

@brendandburns I have one doubt, I was working on util/src/test/java/io/kubernetes/client/informer/cache/SharedProcessorTest.java, particularly on:

java/util/src/test/java/io/kubernetes/client/informer/cache/SharedProcessorTest.java

Lines 27 to 60 in 536f725

    
           @Test 
        
           public void testListenerAddition() throws InterruptedException { 
        
             SharedProcessor<V1Pod> sharedProcessor = new SharedProcessor<>(); 
        
             V1Pod foo1 = new V1Pod().metadata(new V1ObjectMeta().name("foo1").namespace("default")); 
        
             ProcessorListener.Notification<V1Pod> addNotification = 
        
                 new ProcessorListener.AddNotification<V1Pod>(foo1); 
        
             ProcessorListener.Notification<V1Pod> updateNotification = 
        
                 new ProcessorListener.UpdateNotification<V1Pod>(null, foo1); 
        
             ProcessorListener.Notification<V1Pod> deleteNotification = 
        
                 new ProcessorListener.DeleteNotification<V1Pod>(foo1); 
        
             ExpectingNoticationHandler<V1Pod> expectAddHandler = 
        
                 new ExpectingNoticationHandler<V1Pod>(addNotification); 
        
             ExpectingNoticationHandler<V1Pod> expectUpdateHandler = 
        
                 new ExpectingNoticationHandler<V1Pod>(updateNotification); 
        
             ExpectingNoticationHandler<V1Pod> expectDeleteHandler = 
        
                 new ExpectingNoticationHandler<V1Pod>(deleteNotification); 
        
             sharedProcessor.addAndStartListener(expectAddHandler); 
        
             sharedProcessor.addAndStartListener(expectUpdateHandler); 
        
             sharedProcessor.addAndStartListener(expectDeleteHandler); 
        
             sharedProcessor.distribute(addNotification, false); 
        
             sharedProcessor.distribute(updateNotification, false); 
        
             sharedProcessor.distribute(deleteNotification, false); 
        
             // sleep 1s for notification distribution completing 
        
             Thread.sleep(1000); 
        
             assertTrue(expectAddHandler.isSatisfied()); 
        
             assertTrue(expectUpdateHandler.isSatisfied()); 
        
             assertTrue(expectDeleteHandler.isSatisfied()); 
        
           }

I can create a semaphore and acquire it, blocking the main thread, but how will I release so that blocked main thread will continue the execution, I looked at many tests, facing similar problem in many of them.

Edit-
I cannot access ExecutorService instance variable which would have been useful over here, please suggest.

what are the things I need to learn in order to start contributiing to this project?

@brendandburns

@brendandburns ping

/assign

@brendandburns

@brendandburns Is this issue still open. I would like to fix these tests.

test: replace Thread.sleep with sync primitives in tests

test: replace remaining Thread.sleep calls with sync primitives

@maintainer

Hi @maintainer,
I would like to work on this issue. Could you please assign it to me?

Hey,

I see there are already PRs open for:

To avoid duplicating effort, I'm going to start working on the remaining items from the bottom of the list, beginning with extended/src/test/java/io/kubernetes/client/extended/event/EventCorrelatorTest.java.

/assign

Less time available than I anticipated, so I’m unassigning myself. I’m still planning to work on some of the tests, just without taking ownership of the issue.

/unassign

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[Umbrella Issue] Many tests use Thread.sleep instead of synchronization primitives #1223

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	@Test
	public void testListenerAddition() throws InterruptedException {

	SharedProcessor<V1Pod> sharedProcessor = new SharedProcessor<>();

	V1Pod foo1 = new V1Pod().metadata(new V1ObjectMeta().name("foo1").namespace("default"));
	ProcessorListener.Notification<V1Pod> addNotification =
	new ProcessorListener.AddNotification<V1Pod>(foo1);
	ProcessorListener.Notification<V1Pod> updateNotification =
	new ProcessorListener.UpdateNotification<V1Pod>(null, foo1);
	ProcessorListener.Notification<V1Pod> deleteNotification =
	new ProcessorListener.DeleteNotification<V1Pod>(foo1);

	ExpectingNoticationHandler<V1Pod> expectAddHandler =
	new ExpectingNoticationHandler<V1Pod>(addNotification);
	ExpectingNoticationHandler<V1Pod> expectUpdateHandler =
	new ExpectingNoticationHandler<V1Pod>(updateNotification);
	ExpectingNoticationHandler<V1Pod> expectDeleteHandler =
	new ExpectingNoticationHandler<V1Pod>(deleteNotification);

	sharedProcessor.addAndStartListener(expectAddHandler);
	sharedProcessor.addAndStartListener(expectUpdateHandler);
	sharedProcessor.addAndStartListener(expectDeleteHandler);

	sharedProcessor.distribute(addNotification, false);
	sharedProcessor.distribute(updateNotification, false);
	sharedProcessor.distribute(deleteNotification, false);
	// sleep 1s for notification distribution completing
	Thread.sleep(1000);

	assertTrue(expectAddHandler.isSatisfied());
	assertTrue(expectUpdateHandler.isSatisfied());
	assertTrue(expectDeleteHandler.isSatisfied());
	}

[Umbrella Issue] Many tests use Thread.sleep instead of synchronization primitives #1223

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brendandburns commented on Sep 3, 2020

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