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From "Chris Nauroth (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-12529) UserGroupInformation equals method depend on the subject object address
Date Mon, 02 Nov 2015 20:40:28 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-12529?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14985986#comment-14985986
] 

Chris Nauroth commented on HADOOP-12529:
----------------------------------------

Clarifying my earlier comment, I didn't mean to suggest that we should immediately close this
as Won't Fix.  If there is an opportunity to optimize for proxy users at our layer and prevent
the need for downstream applications to build a cache, then that's helpful for the whole ecosystem.

However, this is such a sensitive piece of logic that I'd want to see a diligent review across
the ecosystem to check for mutable usage of proxy user UGI instances.  I'd also want to see
a thorough code review from multiple committers.  I would not advocate committing a patch
for this unless people are willing to put in that effort.

To summarize, I see the proposal as potentially helpful, but also highly risky.  Thanks!

> UserGroupInformation equals method depend on the subject object address
> -----------------------------------------------------------------------
>
>                 Key: HADOOP-12529
>                 URL: https://issues.apache.org/jira/browse/HADOOP-12529
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: security
>    Affects Versions: 2.7.1
>            Reporter: wangwenli
>
>  my question is    why UserGroupInformation equals method depend on the subject object?
>        try below code which is extract from HiveMetaStore:
> {code:title=TestUgi.java|borderStyle=solid}
> UserGroupInformation clientUgi = null;
> UserGroupInformation clientUgi2 = null;
> try {
> clientUgi = UserGroupInformation.createProxyUser("user2", UserGroupInformation.getLoginUser());
> clientUgi2 = UserGroupInformation.createProxyUser("user2", UserGroupInformation.getLoginUser());
> if (clientUgi.equals(clientUgi2)) {
> System.out.println("==");
> } else {
> System.out.println("!=");           //  strangely  this will be hit
> }
> } catch (IOException e1) {
> e1.printStackTrace();
> }
> {code}
>       i found that it is because the equal method from UserGroupInformation is compare
on subject object ref : subject == ((UserGroupInformation) o).subject;  .    
>      as you know,   ipc.Client connect to namenode,   connections.get(ConnectionId) 
  this code will try to reuse the same socket to namenode, but because of ConnectionId's equal
depend on ugi equal, which will cause connections.get(ConnectionId) cann't get the same socket,
  suppose many connect to HiveMetaStore, then many connection to Namenode will established.
>       so my doubts is why UserGroupInformation is compare on subject object ref : subject
== ((UserGroupInformation) o).subject,   it should compare on subject's principal,  am i right?



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