We implement the "context dependent switching" of the execution
environments (cluster / local / test) with static variables in the
ExecutionEnvironment.
That means that these environments are potentially shared between multiple
threads that run programs (also in case where they run one after the other).
This may lead to exceptions, as we sometimes see in the tests, when using
forked test execution: The later test in the same JVM may access the same
environment object as the prior ones. In particular, we see that half
finished programs may still be associated with the execution environment,
such that mixes between programs occur, producing hard to understand cast
exceptions (see trace below)
This is so far only relevant to tests with forked execution, but may become
relevant to users that build different programs at the same time.
I propose to change the static members from environments to environment
factories. That way, we can switch type of environment depending on the
context as before, and we guarantee that each call to
"ExecutionEnvironment.getEnvironment()" returns a dedicated and fresh
environment.
Running org.apache.flink.api.scala.operators.translation.DistinctTranslationTest
java.lang.ClassCastException:
org.apache.flink.api.common.operators.base.DeltaIterationBase cannot
be cast to org.apache.flink.api.common.operators.base.GroupReduceOperatorBase
at
org.apache.flink.api.scala.operators.translation.DistinctTranslationTest.testCombinable(DistinctTranslationTest.scala:39)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at
org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
at
org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at
org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
at
org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
at
org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
at
org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
at
org.apache.maven.surefire.junit4.JUnit4Provider.execute(JUnit4Provider.java:264)
at
org.apache.maven.surefire.junit4.JUnit4Provider.executeTestSet(JUnit4Provider.java:153)
at
org.apache.maven.surefire.junit4.JUnit4Provider.invoke(JUnit4Provider.java:124)
at
org.apache.maven.surefire.booter.ForkedBooter.invokeProviderInSameClassLoader(ForkedBooter.java:200)
at
org.apache.maven.surefire.booter.ForkedBooter.runSuitesInProcess(ForkedBooter.java:153)
at
org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:103)
Tests run: 1, Failures: 1, Errors: 0, Skipped: 0, Time elapsed: 0.027
sec <<< FAILURE! - in
org.apache.flink.api.scala.operators.translation.DistinctTranslationTest
testCombinable(org.apache.flink.api.scala.operators.translation.DistinctTranslationTest)
Time elapsed: 0.024 sec <<< FAILURE!
java.lang.AssertionError:
org.apache.flink.api.common.operators.base.DeltaIterationBase cannot
be cast to org.apache.flink.api.common.operators.base.GroupReduceOperatorBase
at org.junit.Assert.fail(Assert.java:88)
at
org.apache.flink.api.scala.operators.translation.DistinctTranslationTest.testCombinable(DistinctTranslationTest.scala:46)
