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https://issues.apache.org/jira/browse/HDFS-3702?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14220259#comment-14220259
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stack commented on HDFS-3702:
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Nice. Thanks for picking this up [~eddyxu] again.
nit: why have the temporary tempExcluded variable in below?
1369 DatanodeInfo[] tempExcluded = ObjectArrays.concat(
1370 excluded, excludedLocalNodes, DatanodeInfo.class);
1371 excluded = tempExcluded;
Would be coolio if at least a trace logging I could enable for a few seconds to
ensure this feature was working properly when enabled?
Are there other cases in the codebase that you know of where the DN
NetUtils.getHostname() works as a key for finding the datanode info in the NN?
As I read it, we are doing an extra trip to the NN when we open a DFSOS with
AVOID_LOCAL_COPY set? No means of doing doing this once only or once every so
often rather than on each time (not a blocker for the hbase case I'd say but
would be good to avoid or mitigate if possible).
Thanks again for working on this one.
> Add an option for NOT writing the blocks locally if there is a datanode on
> the same box as the client
> -----------------------------------------------------------------------------------------------------
>
> Key: HDFS-3702
> URL: https://issues.apache.org/jira/browse/HDFS-3702
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: hdfs-client
> Affects Versions: 2.5.1
> Reporter: Nicolas Liochon
> Assignee: Lei (Eddy) Xu
> Priority: Minor
> Attachments: HDFS-3702.000.patch, HDFS-3702.001.patch
>
>
> This is useful for Write-Ahead-Logs: these files are writen for recovery
> only, and are not read when there are no failures.
> Taking HBase as an example, these files will be read only if the process that
> wrote them (the 'HBase regionserver') dies. This will likely come from a
> hardware failure, hence the corresponding datanode will be dead as well. So
> we're writing 3 replicas, but in reality only 2 of them are really useful.
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