[jira] [Created] (YARN-3491) Improve the public resource localization to do both FSDownload submission to the thread pool and completed localization handling in one thread (PublicLocalizer).

["zhihai xu (JIRA)" <ji...@apache.org>]

zhihai xu created YARN-3491:
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             Summary: Improve the public resource localization to do both FSDownload submission to the thread pool and completed localization handling in one thread (PublicLocalizer).
                 Key: YARN-3491
                 URL: https://issues.apache.org/jira/browse/YARN-3491
             Project: Hadoop YARN
          Issue Type: Improvement
          Components: nodemanager
    Affects Versions: 2.7.0
            Reporter: zhihai xu
            Assignee: zhihai xu
            Priority: Critical


Improve the public resource localization to do both FSDownload submission to the thread pool and completed localization handling in one thread (PublicLocalizer).
Currently FSDownload submission to the thread pool is done in PublicLocalizer#addResource which is running in Dispatcher thread and completed localization handling is done in PublicLocalizer#run which is running in PublicLocalizer thread.
Because FSDownload submission to the thread pool at the following code is time consuming, the thread pool can't be fully utilized. Instead of doing public resource localization in parallel(multithreading), public resource localization is serialized most of the time.
{code}
            synchronized (pending) {
              pending.put(queue.submit(new FSDownload(lfs, null, conf,
                  publicDirDestPath, resource, request.getContext().getStatCache())),
                  request);
            }
{code}

Also there are two more benefits with this change:
1. The Dispatcher thread won't be blocked by above FSDownload submission. Dispatcher thread handles most of time critical events at Node manager.
2. don't need synchronization on HashMap (pending).
Because pending will be only accessed in PublicLocalizer thread.



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