[jira] [Updated] (HDFS-14862) Review of MovedBlocks

["David Mollitor (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HDFS-14862?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

David Mollitor updated HDFS-14862:
----------------------------------
    Status: Patch Available  (was: Open)

> Review of MovedBlocks
> ---------------------
>
>                 Key: HDFS-14862
>                 URL: https://issues.apache.org/jira/browse/HDFS-14862
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: balancer & mover
>    Affects Versions: 3.2.0
>            Reporter: David Mollitor
>            Assignee: David Mollitor
>            Priority: Minor
>         Attachments: HDFS-14862.1.patch
>
>
> Internal data structure needs to be protected (synchronized) but is scoped as {{protected}} so any sub-class could modify without a lock.  Synchronize the collection itself for protection.  It also returns the internal data structure in {{getLocations}} so the structure could be modified outside of the lock.  Create a copy instead.
> {code:java}
>     /** The locations of the replicas of the block. */
>     protected final List<L> locations = new ArrayList<L>(3);
>     
>     public Locations(Block block) {
>       this.block = block;
>     }
>     
>     /** clean block locations */
>     public synchronized void clearLocations() {
>       locations.clear();
>     }
> ...
>    /** @return its locations */
>     public synchronized List<L> getLocations() {
>       return locations;
>     }
> {code}
>  
> [https://github.com/apache/hadoop/blob/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/balancer/MovedBlocks.java#L43]
> Also, remove a bunch of superfluous and complicated code.



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