[Hadoop-common-dev] [jira] Created: (HADOOP-4984) Code to create the UI display string for queues in the Capacity Scheduler needs to be synchronized, and needs to better update its information

Code to create the UI display string for queues in the Capacity Scheduler needs to be synchronized, and needs to better update its information
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Key: HADOOP-4984
URL: https://issues.apache.org/jira/browse/HADOOP-4984
Project: Hadoop Core
Issue Type: Bug
Components: contrib/capacity-sched
Reporter: Vivek Ratan


There are a couple of problems with _SchedulingInfo.toString()_, the code which creates the UI display string for a queue:
* it needs synchronized access to the _QueueSchedulingInfo_ object, as this same object can be updated by the reclaim-capacity thread, and during a heartbeat.
* the code directly updates its count of running map/reduce tasks. this should be done in a better way, perhaps by calling updateQSIObjects(), rather than walking through the data structures directly. It's also not clear that we want to pay the performance penalty of updating the structures. it maybe OK to provide slightly stale info (the 'staleness' is tiny, in a steady-state and large system, where heartbeats are coming in frequently).