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https://issues.apache.org/jira/browse/HDFS-8855?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14943802#comment-14943802
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Xiaobing Zhou commented on HDFS-8855:
-------------------------------------
This issue is from DataNodeUGIProvider#tokenUGI
{code}
Token<DelegationTokenIdentifier> token = params.delegationToken();
ByteArrayInputStream buf =
new ByteArrayInputStream(token.getIdentifier());
DataInputStream in = new DataInputStream(buf);
DelegationTokenIdentifier id = new DelegationTokenIdentifier();
id.readFields(in);
UserGroupInformation ugi = id.getUser();
ugi.addToken(token);
return ugi;
{code}
for every request, a brand new UGI will be created even with HDFS-7597 patch,
because DelegationTokenIdentifier is initialized per request, although
HDFS-7597 returns the same UGI for the same DelegationTokenIdentifier instance.
> Webhdfs client leaks active NameNode connections
> ------------------------------------------------
>
> Key: HDFS-8855
> URL: https://issues.apache.org/jira/browse/HDFS-8855
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: webhdfs
> Reporter: Bob Hansen
> Assignee: Xiaobing Zhou
> Attachments: HDFS-8855.005.patch, HDFS-8855.006.patch,
> HDFS-8855.007.patch, HDFS-8855.1.patch, HDFS-8855.2.patch, HDFS-8855.3.patch,
> HDFS-8855.4.patch, HDFS_8855.prototype.patch
>
>
> The attached script simulates a process opening ~50 files via webhdfs and
> performing random reads. Note that there are at most 50 concurrent reads,
> and all webhdfs sessions are kept open. Each read is ~64k at a random
> position.
> The script periodically (once per second) shells into the NameNode and
> produces a summary of the socket states. For my test cluster with 5 nodes,
> it took ~30 seconds for the NameNode to have ~25000 active connections and
> fails.
> It appears that each request to the webhdfs client is opening a new
> connection to the NameNode and keeping it open after the request is complete.
> If the process continues to run, eventually (~30-60 seconds), all of the
> open connections are closed and the NameNode recovers.
> This smells like SoftReference reaping. Are we using SoftReferences in the
> webhdfs client to cache NameNode connections but never re-using them?
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