Intermittent failure in TaskExecutorRepeatTemplateAsynchronousTests

[fmbenhassine]

TaskExecutorRepeatTemplateAsynchronousTests#testThrottleLimit fails intermittently with an ArrayIndexOutOfBoundsException, see build log.

[hpoettker]

The error that I can reproduce by executing the test thousands of times is:

java.lang.ArrayIndexOutOfBoundsException: Index 1 out of bounds for length 0
  at java.base/java.util.ArrayList.add(ArrayList.java:455)
  at java.base/java.util.ArrayList.add(ArrayList.java:467)
  at org.springframework.batch.repeat.support.TaskExecutorRepeatTemplateAsynchronousTests$6.doInIteration(TaskExecutorRepeatTemplateAsynchronousTests.java:187)
  at org.springframework.batch.repeat.support.TaskExecutorRepeatTemplate$ExecutingRunnable.run(TaskExecutorRepeatTemplate.java:261)
  at org.springframework.core.task.SimpleAsyncTaskExecutor$ConcurrencyThrottlingRunnable.run(SimpleAsyncTaskExecutor.java:285)
  at java.base/java.lang.Thread.run(Thread.java:833)

It's thrown here:

spring-batch/spring-batch-infrastructure/src/test/java/org/springframework/batch/repeat/support/TaskExecutorRepeatTemplateAsynchronousTests.java

Line 187 in e67c006

items.add("" + item);

The issue seems to be that the callback is executed concurrently while items and threadNames are not thread-safe collections.