Coalescing bulkloader sample

[sheepdreamofandroids]

Hey Ben,

Looks like you merged without taking the changes?
Anyway, here's the PR again. Better luck this time!

cheers, Guus

[coveralls]

Coverage increased (+0.2%) to 93.737% when pulling d59d8dc on sheepdreamofandroids:coalescing-bulkloader-sample into a915558 on ben-manes:master.

[ben-manes]

Thanks! Can you please take a quick look at this test failure? It seems like a race condition because if I run with a mvn clean test it passes, but not with a subsequent mvn test.

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running com.github.benmanes.caffeine.examples.coalescing.bulkloader.CoalescingBulkloaderTest
whenEnoughKeysAreRequestedTheLoadWillHappenImmediately[0](com.github.benmanes.caffeine.examples.coalescing.bulkloader.CoalescingBulkloaderTest) failed, 2 attempts left.
maxDelayIsNotMissedTooMuch[1](com.github.benmanes.caffeine.examples.coalescing.bulkloader.CoalescingBulkloaderTest) failed, 2 attempts left.
maxDelayIsNotMissedTooMuch[2](com.github.benmanes.caffeine.examples.coalescing.bulkloader.CoalescingBulkloaderTest) failed, 2 attempts left.
maxDelayIsNotMissedTooMuch[2](com.github.benmanes.caffeine.examples.coalescing.bulkloader.CoalescingBulkloaderTest) failed, 1 attempts left.
maxDelayIsNotMissedTooMuch[2](com.github.benmanes.caffeine.examples.coalescing.bulkloader.CoalescingBulkloaderTest) failed, 0 attempts left.
Tests run: 6, Failures: 1, Errors: 0, Skipped: 0, Time elapsed: 0.76 sec <<< FAILURE!
maxDelayIsNotMissedTooMuch[2](com.github.benmanes.caffeine.examples.coalescing.bulkloader.CoalescingBulkloaderTest)  Time elapsed: 0.232 sec  <<< FAILURE!
java.lang.AssertionError:
Expected: is <1>
     but: was <0>
	at org.hamcrest.MatcherAssert.assertThat(MatcherAssert.java:20)
	at org.junit.Assert.assertThat(Assert.java:956)
	at org.junit.Assert.assertThat(Assert.java:923)
	at com.github.benmanes.caffeine.examples.coalescing.bulkloader.CoalescingBulkloaderTest.maxDelayIsNotMissedTooMuch(CoalescingBulkloaderTest.java:98)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:567)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at com.github.benmanes.caffeine.examples.coalescing.bulkloader.CoalescingBulkloaderTest$1.try_(CoalescingBulkloaderTest.java:152)
	at com.github.benmanes.caffeine.examples.coalescing.bulkloader.CoalescingBulkloaderTest$1.try_(CoalescingBulkloaderTest.java:156)
	at com.github.benmanes.caffeine.examples.coalescing.bulkloader.CoalescingBulkloaderTest$1.try_(CoalescingBulkloaderTest.java:156)
	at com.github.benmanes.caffeine.examples.coalescing.bulkloader.CoalescingBulkloaderTest$1.evaluate(CoalescingBulkloaderTest.java:147)
	at org.junit.rules.RunRules.evaluate(RunRules.java:20)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
	at org.junit.runners.Suite.runChild(Suite.java:128)
	at org.junit.runners.Suite.runChild(Suite.java:27)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
	at org.apache.maven.surefire.junit4.JUnit4Provider.execute(JUnit4Provider.java:252)
	at org.apache.maven.surefire.junit4.JUnit4Provider.executeTestSet(JUnit4Provider.java:141)
	at org.apache.maven.surefire.junit4.JUnit4Provider.invoke(JUnit4Provider.java:112)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:567)
	at org.apache.maven.surefire.util.ReflectionUtils.invokeMethodWithArray(ReflectionUtils.java:189)
	at org.apache.maven.surefire.booter.ProviderFactory$ProviderProxy.invoke(ProviderFactory.java:165)
	at org.apache.maven.surefire.booter.ProviderFactory.invokeProvider(ProviderFactory.java:85)
	at org.apache.maven.surefire.booter.ForkedBooter.runSuitesInProcess(ForkedBooter.java:115)
	at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:75)


Results :

Failed tests:   maxDelayIsNotMissedTooMuch[2](com.github.benmanes.caffeine.examples.coalescing.bulkloader.CoalescingBulkloaderTest): (..)

Tests run: 6, Failures: 1, Errors: 0, Skipped: 0

[sheepdreamofandroids]

Hmmm, I can't make it fail locally. Can you tell me a bit more about your environment, like OS and java version used for running the test? Does it still fail when you increase the delta constant in the test?

[ben-manes]

Yes, it seems to fail regardless of which constant I increase. I am running on OS X Mojave with JDK 1.8.0_144. It also fails when switching to JDK 11.0.1

[ben-manes]

Sorry we never got this resolved. I had the same failures locally, but after playing around it started working properly and I cannot get it to fail anymore. I'll merge, since its been far too long.

[ben-manes]

haha, and it failed again locally. It is flaky on my laptop unfortunately.

[sheepdreamofandroids]

Hey Ben, I managed to make it fail on my laptop as well. But only by running 8 benchmarks in parallel in the background and even then only sometimes. Since this test is sensitive to timing I don't think it is anything to worry about.
The reason that it fails more often on your mac might be that (AFAIK) a mac prioritizes GUI over other processes. As long as CI is unaffected I guess that's OK.

[ben-manes]

Thanks for looking into it! Reviewing the tests it makes sense to be flaky because sleep() is the minimum time rather than a hard real-time guarantee. I agree as long as it’s stable on CI that’s good enough.