@Override
  public ExecutorService getTaskExecutor(Config config) {
    int threadPoolSize = new JobConfig(config).getThreadPoolSize();

    return Executors.newFixedThreadPool(threadPoolSize,
        new ThreadFactoryBuilder().setNameFormat("Samza Container Thread-%d").build());
  }
Default factory for creating the executor used when running tasks in multi-thread mode.
samza-core/src/main/java/org/apache/samza/task/DefaultTaskExecutorFactory.java