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From "Yi Liu (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-8884) Improve BlockPlacementPolicyDefault#chooseTarget to check candidate datanode first
Date Tue, 11 Aug 2015 07:58:45 GMT

     [ https://issues.apache.org/jira/browse/HDFS-8884?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Yi Liu updated HDFS-8884:
-------------------------
    Attachment: HDFS-8884.001.patch

> Improve BlockPlacementPolicyDefault#chooseTarget to check candidate datanode first 
> -----------------------------------------------------------------------------------
>
>                 Key: HDFS-8884
>                 URL: https://issues.apache.org/jira/browse/HDFS-8884
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>            Reporter: Yi Liu
>            Assignee: Yi Liu
>         Attachments: HDFS-8884.001.patch
>
>
> In current BlockPlacementPolicyDefault, when choosing datanode storage to place block,
we have following logic:
> {code}
>         final DatanodeStorageInfo[] storages = DFSUtil.shuffle(
>             chosenNode.getStorageInfos());
>         int i = 0;
>         boolean search = true;
>         for (Iterator<Map.Entry<StorageType, Integer>> iter = storageTypes
>             .entrySet().iterator(); search && iter.hasNext(); ) {
>           Map.Entry<StorageType, Integer> entry = iter.next();
>           for (i = 0; i < storages.length; i++) {
>             StorageType type = entry.getKey();
>             final int newExcludedNodes = addIfIsGoodTarget(storages[i],
> {code}
> We will iterate (actually two {{for}}) all storages of the candidate datanode even the
datanode itself is not good (e.g. decommissioned, stale, too busy..), since currently we do
all the check in {{addIfIsGoodTarget}}.
> We can fail-fast: check the datanode related conditions first, if the datanode is not
good, then no need to shuffle and iterate the storages. Then it's more efficient.



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