[KAFKA-8630] Unit testing a streams processor with a WindowStore throws a ClassCastException

• Type: Bug
• Status: Resolved
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: 2.3.0
• Fix Version/s: 2.7.0, 2.6.1
• Component/s: streams-test-utils
• Assignee: John Roesler
• Reporter: Justin Fetherolf
• Created: 04/Jul/19 13:01
• Updated: 20/Oct/20 21:35
• Resolved: 20/Oct/20 21:35

Description

I was attempting to write a unit test for a class implementing the Processor interface that contained a WindowStore, but running the test fails with a ClassCastException coming out of InMemoryWindowStore.init attempting to cast MockProcessorContext to InternalProcessorContext.

Minimal code to reproduce:

package com.cantgetthistowork;

import org.apache.kafka.streams.processor.Processor;
import org.apache.kafka.streams.processor.ProcessorContext;
import org.apache.kafka.streams.state.WindowStore;

public class InMemWindowProcessor implements Processor<String, String> {

  private ProcessorContext context;
  private WindowStore<String, String> windowStore;

  @Override
  public void init(ProcessorContext context) {
    this.context = context;

    windowStore = (WindowStore<String, String>) context.getStateStore("my-win-store");
  }

  @Override
  public void process(String key, String value) {
  }

  @Override
  public void close() {
  }

}

package com.cantgetthistowork;

import java.time.Duration;
import java.time.Instant;

import org.apache.kafka.common.serialization.Serdes;
import org.apache.kafka.streams.processor.MockProcessorContext;
import org.apache.kafka.streams.state.Stores;
import org.apache.kafka.streams.state.WindowStore;
import org.junit.Before;
import org.junit.Test;

public class InMemWindowProcessorTest {

  InMemWindowProcessor processor = null;
  MockProcessorContext context = null;

  @Before
  public void setup() {
    processor = new InMemWindowProcessor();
    context = new MockProcessorContext();

    WindowStore<String, String> store =
      Stores.windowStoreBuilder(
        Stores.inMemoryWindowStore(
          "my-win-store",
          Duration.ofMinutes(10),
          Duration.ofSeconds(10),
          false
        ),
        Serdes.String(),
        Serdes.String()
      )
      .withLoggingDisabled()
      .build();
    store.init(context, store);
    context.register(store, null);
    processor.init(context);
  }

  @Test
  public void testThings() {
    Instant baseTime = Instant.now();
    context.setTimestamp(baseTime.toEpochMilli());
    context.setTopic("topic-name");
    processor.process("key1", "value1");
  }

}

 

I was trying this with maven, with mvn --version outputting:

Apache Maven 3.5.0 (ff8f5e7444045639af65f6095c62210b5713f426; 2017-04-03T13:39:06-06:00)
Maven home: ~/opt/apache-maven-3.5.0
Java version: 1.8.0_212, vendor: Oracle Corporation
Java home: /usr/lib/jvm/java-8-openjdk-amd64/jre
Default locale: en_US, platform encoding: UTF-8
OS name: "linux", version: "4.15.0-52-generic", arch: "amd64", family: "unix"

And finally the stack trace:

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running com.cantgetthistowork.InMemWindowProcessorTest
SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.
Tests run: 1, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 0.076 sec <<< FAILURE!
testThings(com.cantgetthistowork.InMemWindowProcessorTest)  Time elapsed: 0.05 sec  <<< ERROR!
java.lang.ClassCastException: org.apache.kafka.streams.processor.MockProcessorContext cannot be cast to org.apache.kafka.streams.processor.internals.InternalProcessorContext
    at org.apache.kafka.streams.state.internals.InMemoryWindowStore.init(InMemoryWindowStore.java:91)
    at org.apache.kafka.streams.state.internals.WrappedStateStore.init(WrappedStateStore.java:48)
    at org.apache.kafka.streams.state.internals.MeteredWindowStore.init(MeteredWindowStore.java:90)
    at com.cantgetthistowork.InMemWindowProcessorTest.setup(InMemWindowProcessorTest.java:36)
    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:498)
    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.RunBefores.evaluate(RunBefores.java:24)
    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$2.evaluate(ParentRunner.java:268)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.apache.maven.surefire.junit4.JUnit4Provider.execute(JUnit4Provider.java:252)
    at org.apache.maven.surefire.junit4.JUnit4Provider.executeTestSet(JUnit4Provider.java:141)
    at org.apache.maven.surefire.junit4.JUnit4Provider.invoke(JUnit4Provider.java:112)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.apache.maven.surefire.util.ReflectionUtils.invokeMethodWithArray(ReflectionUtils.java:189)
    at org.apache.maven.surefire.booter.ProviderFactory$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 :

Tests in error: 
  testThings(com.cantgetthistowork.InMemWindowProcessorTest): org.apache.kafka.streams.processor.MockProcessorContext cannot be cast to org.apache.kafka.streams.processor.internals.InternalProcessorContext

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

 

 

Issue Links

• duplicates: KAFKA-10200 MockProcessorContext doesn't work with WindowStores
• is related to: KAFKA-9109 Get Rid of Cast from ProcessorContext to InternalProcessorContext
• relates to: KAFKA-9088 Consolidate InternalMockProcessorContext and MockInternalProcessorContext