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From "Hong Zhiguo (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (YARN-4002) make ResourceTrackerService.nodeHeartbeat more concurrent
Date Mon, 21 Mar 2016 02:16:33 GMT

     [ https://issues.apache.org/jira/browse/YARN-4002?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Hong Zhiguo updated YARN-4002:
    Attachment: YARN-4002-rwlock-v2.patch

Uploaded YARN-4002-rwlock-v2.patch for an improvement: make the read side critical section
    try {
      hostsList = hostsReader.getHosts();
      excludeList = hostsReader.getExcludedHosts();
    } finally {

As explained by [~rohithsharma], this prevents mixing up old value of hostsReader.getHosts()
and new value of hostsReader.getExcludedHosts(). And this is the only reason someone may prefer
rwlock solution than lockless one.

If the mixing up is not thought (for example, by meself) a problem, lockless solution is good

> make ResourceTrackerService.nodeHeartbeat more concurrent
> ---------------------------------------------------------
>                 Key: YARN-4002
>                 URL: https://issues.apache.org/jira/browse/YARN-4002
>             Project: Hadoop YARN
>          Issue Type: Improvement
>            Reporter: Hong Zhiguo
>            Assignee: Hong Zhiguo
>            Priority: Critical
>         Attachments: 0001-YARN-4002.patch, YARN-4002-lockless-read.patch, YARN-4002-rwlock-v2.patch,
YARN-4002-rwlock.patch, YARN-4002-v0.patch
> We have multiple RPC threads to handle NodeHeartbeatRequest from NMs. By design the method
ResourceTrackerService.nodeHeartbeat should be concurrent enough to scale for large clusters.
> But we have a "BIG" lock in NodesListManager.isValidNode which I think it's unnecessary.
> First, the fields "includes" and "excludes" of HostsFileReader are only updated on "refresh
nodes".  All RPC threads handling node heartbeats are only readers.  So RWLock could be used
to  alow concurrent access by RPC threads.
> Second, since he fields "includes" and "excludes" of HostsFileReader are always updated
by "reference assignment", which is atomic in Java, the reader side lock could just be skipped.

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