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Date: Thu, 27 Oct 2016 23:22:58 +0000 (UTC)
From: "Mingliang Liu (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Message-ID: <JIRA.13014793.1477328639000.111691.1477610578989@Atlassian.JIRA>
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References: <JIRA.13014793.1477328639000@Atlassian.JIRA> <JIRA.13014793.1477328639767@arcas>
Subject: [jira] [Updated] (HDFS-11047) Remove deep copies of
 FinalizedReplica to alleviate heap consumption on DataNode
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archived-at: Thu, 27 Oct 2016 23:23:01 -0000


     [ https://issues.apache.org/jira/browse/HDFS-11047?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Mingliang Liu updated HDFS-11047:
---------------------------------
     Hadoop Flags: Reviewed
    Fix Version/s: 3.0.0-alpha2

> Remove deep copies of FinalizedReplica to alleviate heap consumption on DataNode
> --------------------------------------------------------------------------------
>
>                 Key: HDFS-11047
>                 URL: https://issues.apache.org/jira/browse/HDFS-11047
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: datanode
>            Reporter: Xiaobing Zhou
>            Assignee: Xiaobing Zhou
>             Fix For: 3.0.0-alpha2
>
>         Attachments: HDFS-11047.000.patch, HDFS-11047.001.patch, HDFS-11047.002.patch
>
>
> DirectoryScanner does scan by deep copying FinalizedReplica. In a deployment with 500,000+ blocks, we've seen the DN heap usage being accumulated to high peaks very quickly. Deep copies of FinalizedReplica will make DN heap usage even worse if directory scans are scheduled more frequently. This proposes removing unnecessary deep copies since DirectoryScanner#scan already holds lock of dataset.
> DirectoryScanner#scan
> {code}
>     try(AutoCloseableLock lock = dataset.acquireDatasetLock()) {
>       for (Entry<String, ScanInfo[]> entry : diskReport.entrySet()) {
>         String bpid = entry.getKey();
>         ScanInfo[] blockpoolReport = entry.getValue();
>         
>         Stats statsRecord = new Stats(bpid);
>         stats.put(bpid, statsRecord);
>         LinkedList<ScanInfo> diffRecord = new LinkedList<ScanInfo>();
>         diffs.put(bpid, diffRecord);
>         
>         statsRecord.totalBlocks = blockpoolReport.length;
>         List<ReplicaInfo> bl = dataset.getFinalizedBlocks(bpid); /* deep copies here*/
> {code}
> FsDatasetImpl#getFinalizedBlocks
> {code}
>   public List<ReplicaInfo> getFinalizedBlocks(String bpid) {
>     try (AutoCloseableLock lock = datasetLock.acquire()) {
>       ArrayList<ReplicaInfo> finalized =
>           new ArrayList<ReplicaInfo>(volumeMap.size(bpid));
>       for (ReplicaInfo b : volumeMap.replicas(bpid)) {
>         if (b.getState() == ReplicaState.FINALIZED) {
>           finalized.add(new ReplicaBuilder(ReplicaState.FINALIZED)
>               .from(b).build()); /* deep copies here*/
>         }
>       }
>       return finalized;
>     }
>   }
> {code}



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