David Mollitor created HDFS-14862:
-------------------------------------
Summary: 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
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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