partitioned-batch-job raises NPE when used with mutiple Partiton handlers

Start with the partitioned-batch-job sample and inspect DeployerPartitionHandler.launchWorker at line 347, where taskExecution is reported as null when multiple partition handlers are configured. Run the sample with two or more handlers and compare the execution path with a single handler. Done means the multi-handler job completes without the NullPointerException and the behavior is covered by a regression check.

Hello,

I modified the partitioned-batch-job sample such that to add the following method:

  @Bean
  public PartitionHandler partitionHandler2(TaskLauncher taskLauncher, JobExplorer jobExplorer, TaskRepository taskRepository)
  {
    Resource resource = this.resourceLoader.getResource("maven://fr.simplex_software.tests:partitioned-job:1.0-SNAPSHOT");
    DeployerPartitionHandler partitionHandler = new DeployerPartitionHandler(taskLauncher, jobExplorer, resource, "workerStep");
    List<String> commandLineArgs = new ArrayList<>(3);
    commandLineArgs.add("--spring.profiles.active=worker");
    commandLineArgs.add("--spring.cloud.task.initialize-enabled=false");
    commandLineArgs.add("--spring.batch.initializer.enabled=false");
    partitionHandler.setCommandLineArgsProvider(new PassThroughCommandLineArgsProvider(commandLineArgs));
    partitionHandler.setEnvironmentVariablesProvider(new SimpleEnvironmentVariablesProvider(this.environment));
    partitionHandler.setMaxWorkers(2);
    partitionHandler.setApplicationName("PartitionedBatchJobTask");
    return partitionHandler;
  }

Running the job raises the following exception:

2021-08-06 13:12:47.071 DEBUG 13084 --- [           main] o.s.c.t.r.support.SimpleTaskRepository   : Creating: 
TaskExecution{executionId=149, parentExecutionId=null, exitCode=null, taskName='null', startTime=null, endTime=null, 
exitMessage='null', externalExecutionId='null', errorMessage='null', arguments=[]}
2021-08-06 13:12:47.074 ERROR 13084 --- [           main] o.s.batch.core.step.AbstractStep         : Encountered an error 
executing step step1 in job partitionedJob-494091066

java.lang.NullPointerException: null
     at 
    org.springframework.cloud.task.batch.partition.DeployerPartitionHandler.launchWorker(DeployerPartitionHandler.java:347) 
    ~[spring-cloud-task-batch-2.3.3.jar:2.3.3]
     at 
    org.springframework.cloud.task.batch.partition.DeployerPartitionHandler.launchWorkers(DeployerPartitionHandler.java:313) 
    ~ [spring-cloud-task-batch-2.3.3.jar:2.3.3]
    ...

Please advise.

Many thanks in advance.

Just to mention that the NPE is raised at the line #347 of the DeployerPartitionHanlder class cause the taskExecution lcal property is null. This only happens as soon as there are 2 or more partition handlers in the job. Using different flows doesn't change anything.