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https://issues.apache.org/jira/browse/HDFS-4359?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Aaron T. Myers updated HDFS-4359:
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Target Version/s: 2.0.3-alpha
> remove an unnecessary synchronized keyword in BPOfferService.java
> -----------------------------------------------------------------
>
> Key: HDFS-4359
> URL: https://issues.apache.org/jira/browse/HDFS-4359
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: datanode
> Affects Versions: 3.0.0, 2.0.2-alpha
> Reporter: liang xie
> Assignee: liang xie
> Attachments: dn.jstack, HDFS-4359.txt, nn_dns_broken.jstack
>
>
> we encountered a NN&DN hung issue, the DN hung was caused by no NN response
> for heartbeat. Per DN thread dump, i think we can have a little improvement
> on this detail code :
> synchronized List<BPServiceActor> getBPServiceActors() {
> return Lists.newArrayList(bpServices);
> }
> the bpServices is declared as :
> private List<BPServiceActor> bpServices =
> new CopyOnWriteArrayList<BPServiceActor>();
> It's a thread-safe variant indead, so we can remove the above synchronized
> keyword safely, IMHO.
> Here is a simple statistic for thread dump:
> xieliang@xieliang:/tmp$ grep 0x00000007b00289f0 dn.jstack |wc -l
> 252
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