code: public void recordKilledTask(String trackerName) {
      synchronized (this) {
        NodeUsageReport usageReport = getReportUnprotected(trackerName);
        usageReport.setNumKilled(usageReport.getNumKilled() + 1);
      }
    }
docs: Increment the number of killed tasks on a tracker.
  @param trackerName The name of the tracker.