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https://issues.apache.org/jira/browse/HADOOP-9747?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16345576#comment-16345576
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Bharat Viswanadham commented on HADOOP-9747:
--------------------------------------------
Hi [~daryn]
Thanks for reply.
# In getLoginUser(), there can be a still race condition, as setLoginUser()
can be called from loginUserFromSubject/loginUserFromKeytab, which might change
*_loginUserRef._*
Can we update the getLoginUser() as below, this will only penalize during
initial creation of loginUserRef Object.
{code:java}
UserGroupInformation loginUser = logiUserRef;
if (loginUser == null) {
synchronized(UserGroupInformation.class) {
if (loginUser == null) {
loginUser = createLoginUser(null);
loginUserRef = loginUser;
}
}
}
return loginUser;{code}
2. So, for this setLoginUser should be synchronized.
I think this might improvise the code, and also handle race condition. Could
you please let me know your thoughts?
> Reduce unnecessary UGI synchronization
> --------------------------------------
>
> Key: HADOOP-9747
> URL: https://issues.apache.org/jira/browse/HADOOP-9747
> Project: Hadoop Common
> Issue Type: Bug
> Components: security
> Affects Versions: 0.23.0, 2.0.0-alpha, 3.0.0-alpha1
> Reporter: Daryn Sharp
> Assignee: Daryn Sharp
> Priority: Critical
> Attachments: HADOOP-9747-trunk-03.patch, HADOOP-9747-trunk.01.patch,
> HADOOP-9747-trunk.02.patch, HADOOP-9747.2.branch-2.patch,
> HADOOP-9747.2.trunk.patch, HADOOP-9747.branch-2.patch, HADOOP-9747.trunk.patch
>
>
> Jstacks of heavily loaded NNs show up to dozens of threads blocking in the
> UGI.
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