Recently, I have been using SchedulerLoadSimulator to validate the impact of changes on my FairScheduler. I encountered some problems.
Firstly, I fix a npe bug with the patch in https://issues.apache.org/jira/browse/YARN-4302
Secondly, everything seems to be ok, but I just get "" in file realtimetrack.json. Finally, I find the MetricsLogRunnable thread will exit because of npe,
the reason is "wrapper.getQueueSet()" is still null when executing "String metrics = web.generateRealTimeTrackingMetrics();"
So, we should put "String metrics = web.generateRealTimeTrackingMetrics();" in try section to avoid MetricsLogRunnable thread exit with unexpected exception.
My hadoop version is 2.7.2, it seems that hadoop trunk branch also has the second problem and I have made a patch to solve it.