@Override
    public void run() {
      try {
        int ret = ToolRunner.run(HBaseConfiguration.create(), new LoadTestTool(), workerArgs);
        if (ret != 0) {
          throw new RuntimeException("LoadTestTool exit with non-zero return code.");
        }
      } catch (Exception ex) {
        LOG.error("Error in worker thread", ex);
        workerThreadError(ex);
      }
    }
Check for errors in the writer threads. If any is found, rethrow it.
hbase-diagnostics/src/main/java/org/apache/hadoop/hbase/util/LoadTestTool.java