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https://issues.apache.org/jira/browse/HDFS-5394?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13816378#comment-13816378
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Chris Nauroth commented on HDFS-5394:
-------------------------------------
I just tested with patch version 7, and the datanode didn't uncache previously
cached blocks after receiving the DNA_CACHE message. Debug logging shows that
it's due to the following logic in {{FsDatasetCache#uncacheBlock}}. I assume
{{case CACHED}} should be doing the same as the {{default}} block and
submitting an {{UncachingTask}}.
{code}
case CACHED:
if (LOG.isDebugEnabled()) {
LOG.debug("Block with id " + blockId + ", pool " + bpid + " " +
"does not need to be uncached, because it is " +
"in state " + prevValue.state + ".");
}
break;
{code}
> fix race conditions in DN caching and uncaching
> -----------------------------------------------
>
> Key: HDFS-5394
> URL: https://issues.apache.org/jira/browse/HDFS-5394
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: datanode, namenode
> Affects Versions: 3.0.0
> Reporter: Colin Patrick McCabe
> Assignee: Colin Patrick McCabe
> Attachments: HDFS-5394-caching.001.patch,
> HDFS-5394-caching.002.patch, HDFS-5394-caching.003.patch,
> HDFS-5394-caching.004.patch, HDFS-5394.005.patch, HDFS-5394.006.patch,
> HDFS-5394.007.patch
>
>
> The DN needs to handle situations where it is asked to cache the same replica
> more than once. (Currently, it can actually do two mmaps and mlocks.) It
> also needs to handle the situation where caching a replica is cancelled
> before said caching completes.
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