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https://issues.apache.org/jira/browse/HADOOP-16122?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16772628#comment-16772628
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Eric Yang commented on HADOOP-16122:
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{quote}Since the client code must run in the same process to access different
users' HDFS, I'm not sure if proxyUser can do that with different users'
principals as well.{quote}
ProxyUser is specifically designed for multi-user access to HDFS without
exposing end user principals to service. In the event service is compromised,
there is only service principal to regenerate rather than regenerating for all
end user principals and keytab files.
> Re-login from keytab for multiple UGI will use the same and incorrect
> keytabPrincipal
> -------------------------------------------------------------------------------------
>
> Key: HADOOP-16122
> URL: https://issues.apache.org/jira/browse/HADOOP-16122
> Project: Hadoop Common
> Issue Type: Bug
> Components: auth
> Reporter: chendihao
> Priority: Major
>
> In our scenario, we have a service to allow multiple users to access HDFS
> with their keytab. The users use different Hadoop user and permission to
> access the HDFS files. This service will run with multi-threads and create
> independent UGI object for each user and use its own UGI to create Hadoop
> FileSystem object to read/write HDFS.
>
> Since we have multiple Hadoop users in the same process, we have to use
> `loginUserFromKeytabAndReturnUGI` instead of `loginUserFromKeytab`. The
> `loginUserFromKeytabAndReturnUGI` will not do the re-login automatically.
> Then we have to call `checkTGTAndReloginFromKeytab` or `reloginFromKeytab`
> before the kerberos ticket expires.
>
> The issue is that `reloginFromKeytab` will always re-login with the same and
> incorrect keytab instead of the one from the expected UGI object. Because of
> this issue, we can only support multiple Hadoop users to login with their own
> keytabs at the first time but not re-login when the tickets expire. The logic
> of login and re-login is slightly different especially for updating the
> global static properties and it may be the bug of the implementation of that.
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