code: @Override
    public JobID getNewJobId() throws IOException {
      int value = jobCounter.incrementAndGet();
      if (value > 1) {
        throw new RuntimeException(
          "CoronaJobTracker can only run one job! (value=" + value + ")");
      }
      createSession();
      // the jobtracker can run only a single job. it's jobid is fixed based
      // on the sessionId.
      jobId = jobIdFromSessionId(sessionId);
      return jobId;
    }
docs: Returns a unique JobID for a new job.
  CoronaJobTracker can only run a single job and it's id is fixed a-priori
  @return the job ID.