[GitHub] [beam] damccorm opened a new issue, #20869: DirectRunner NullPointerException

[GitBox <gi...@apache.org>]

damccorm opened a new issue, #20869:
URL: https://github.com/apache/beam/issues/20869

   When using the `DirectRunner` in tests I encountered flaky tests due to `NullPointerException`.
   
   When the test fails the relevant stack trace is like below:
   
    
   
    
   ```
   
   java.lang.NullPointerException
    at org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Preconditions.checkNotNull(Preconditions.java:877)
   
   at org.apache.beam.vendor.guava.v26_0_jre.com.google.common.util.concurrent.ThreadFactoryBuilder.setThreadFactory(ThreadFactoryBuilder.java:132)
   
   at org.apache.beam.runners.direct.DirectRunner.run(DirectRunner.java:192)
    at org.apache.beam.runners.direct.DirectRunner.run(DirectRunner.java:67)
   
   at org.apache.beam.sdk.Pipeline.run(Pipeline.java:322)
    at google.registry.beam.TestPipelineExtension.run(TestPipelineExtension.java:344)
   
   at google.registry.beam.TestPipelineExtension.run(TestPipelineExtension.java:324)
    at google.registry.beam.spec11.Spec11PipelineTest.testSuccess_saveToGcs(Spec11PipelineTest.java:185)
   ```
   
    
   
    
   However the null pointer seems to have come from calling (a repackaged and very innocent looking) guava function to set the `ThreadFactory`:
    
   ```
   
    ExecutorService metricsPool =
    Executors.newCachedThreadPool(
    new ThreadFactoryBuilder()
   .setThreadFactory(MoreExecutors.platformThreadFactory())
   
   .setDaemon(false) // otherwise you say you want to leak, please don't!
    .setNameFormat("direct-metrics-counter-committer")
   
   .build());
   ```
   
    
   Which in turn is just calling java.util.concurrent.Executors.defaulThreatFactory() when not on App Engine:
    
   ```
   
   @Beta
   @GwtIncompatible
   public static ThreadFactory platformThreadFactory() {
    if (!isAppEngine())
   {
     return Executors.defaultThreadFactory();
     } else {
    ...
   } 
   ```
   
    
   
   I don't understand how this could possibly have failed. The test seems to be only flaky on our CI servers running Ubuntu and I haven't been able to reproduce it locally, making debugging a challenge.
   
    
   
   I'd appreciate any input you may have. Thanks!
   
   Imported from Jira [BEAM-12215](https://issues.apache.org/jira/browse/BEAM-12215). Original Jira may contain additional context.
   Reported by: jianglai.


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