[jira] [Assigned] (HDFS-12533) NNThroughputBenchmark threads get stuck on UGI.getCurrentUser()

["Erik Krogen (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HDFS-12533?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Erik Krogen reassigned HDFS-12533:
----------------------------------

    Assignee:     (was: Erik Krogen)

> NNThroughputBenchmark threads get stuck on UGI.getCurrentUser()
> ---------------------------------------------------------------
>
>                 Key: HDFS-12533
>                 URL: https://issues.apache.org/jira/browse/HDFS-12533
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>            Reporter: Erik Krogen
>            Priority: Major
>
> In {{NameNode#getRemoteUser()}}, it first attempts to fetch from the RPC user (not a synchronized operation), and if there is no RPC call, it will call {{UserGroupInformation#getCurrentUser()}} (which is {{synchronized}}). This makes it efficient for RPC operations (the bulk) so that there is not too much contention.
> In NNThroughputBenchmark, however, there is no RPC call since we bypass that later, so with a high thread count many of the threads are getting stuck. At one point I attached a profiler and found that quite a few threads had been waiting for {{#getCurrentUser()}} for 2 minutes ( ! ). When taking this away I found some improvement in the throughput numbers I was seeing. To more closely emulate a real NN we should improve this issue.



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