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https://issues.apache.org/jira/browse/HDFS-7331?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14197449#comment-14197449
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Aaron T. Myers commented on HDFS-7331:
--------------------------------------
bq. The size of the map needs to be bounded. A cachemap can do the job.
Why does the size of the map need to be bounded? To take an extreme case, in a
5,000 node cluster we'd be storing maybe an extra 30 bytes for each hostname,
an extra 4 bytes for each IP address, and an extra 8 bytes for each long. Add
in maybe another 32 bytes for object overhead per map entry, and you're looking
at a total of 370KB on each DN. That hardly seems like something to worry
about, considering most DN heaps are multiple GBs in size.
> Add Datanode network counts to datanode jmx page
> ------------------------------------------------
>
> Key: HDFS-7331
> URL: https://issues.apache.org/jira/browse/HDFS-7331
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: datanode
> Reporter: Charles Lamb
> Assignee: Charles Lamb
> Priority: Minor
> Attachments: HDFS-7331.001.patch
>
>
> Add per-datanode counts to the datanode jmx page. For example, networkErrors
> could be exposed like this:
> {noformat}
> }, {
> ...
> "DatanodeNetworkCounts" : "{\"dn1\":{\"networkErrors\":1}}",
> ...
> "NamenodeAddresses" :
> "{\"localhost\":\"BP-1103235125-127.0.0.1-1415057084497\"}",
> "VolumeInfo" :
> "{\"/tmp/hadoop-cwl/dfs/data/current\":{\"freeSpace\":3092725760,\"usedSpace\":28672,\"reservedSpace\":0}}",
> "ClusterId" : "CID-4b38f2ae-5e58-4e15-b3cf-3ba3f46e724e"
> }, {
> {noformat}
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