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https://issues.apache.org/jira/browse/HDFS-12818?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16282322#comment-16282322
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Erik Krogen commented on HDFS-12818:
------------------------------------
Thanks for looking [~shv]!
{{getStorage()}} can never return null:
{code}
private SimulatedStorage getStorage(Block b) {
return storages.get(LongMath.mod(b.getBlockId(), storages.size()));
}
{code}
This will always return one of the values contained within {{storages}} which
does not contain any null values.
{{getBlockMap(b, bpid)}} also cannot return null; it simply passes through to
{{SimulatedStorage#getBlockMap(bpid)}}:
{code}
Map<Block, BInfo> getBlockMap(String bpid) throws IOException {
SimulatedBPStorage bpStorage = map.get(bpid);
if (bpStorage == null) {
throw new IOException("Nonexistent block pool: " + bpid);
}
return bpStorage.getBlockMap();
}
{code}
{{SimulatedBPStorage#getBlockMap()}} returns a {{final}} non-null field so we
are good to go throughout.
I updated the Javadoc comments to make this more clear; attaching v002 patch. I
believe the 1 new checkstyle issue is a long import from a static import in the
test; nothing I can do hence why I did not fix it between v000 and v001.
> Support multiple storages in DataNodeCluster / SimulatedFSDataset
> -----------------------------------------------------------------
>
> Key: HDFS-12818
> URL: https://issues.apache.org/jira/browse/HDFS-12818
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: datanode, test
> Reporter: Erik Krogen
> Assignee: Erik Krogen
> Priority: Minor
> Attachments: HDFS-12818.000.patch, HDFS-12818.001.patch,
> HDFS-12818.002.patch
>
>
> Currently {{SimulatedFSDataset}} (and thus, {{DataNodeCluster}} with
> {{-simulated}}) only supports a single storage per {{DataNode}}. Given that
> the number of storages can have important implications on the performance of
> block report processing, it would be useful for these classes to support a
> multiple storage configuration.
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