private ExecutorService getPool() {
      int maxThreads = 1;
      long keepAliveTime = 60;
      ThreadPoolExecutor pool = new ThreadPoolExecutor(1, maxThreads, keepAliveTime,
        TimeUnit.SECONDS, new SynchronousQueue<>(),
        new ThreadFactoryBuilder().setNameFormat("hbase-table-pool-%d").setDaemon(true)
          .setUncaughtExceptionHandler(Threads.LOGGING_EXCEPTION_HANDLER).build());
      pool.allowCoreThreadTimeOut(true);
      return pool;
    }
@return a pool that has one thread only at every time. A second action added to the pool (
        running concurrently), will cause an exception.
hbase-server/src/test/java/org/apache/hadoop/hbase/coprocessor/TestOpenTableInCoprocessor.java