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From "Gabor Bota (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HADOOP-15622) UserGroupInformation TGT renewer refreshTime should be based on getNextTgtRenewalTime
Date Fri, 20 Jul 2018 13:37:00 GMT
Gabor Bota created HADOOP-15622:

             Summary: UserGroupInformation TGT renewer refreshTime should be based on getNextTgtRenewalTime
                 Key: HADOOP-15622
                 URL: https://issues.apache.org/jira/browse/HADOOP-15622
             Project: Hadoop Common
          Issue Type: Bug
            Reporter: Gabor Bota

 The calculation of nextRefresh in UserGroupInformation is currently based on:

nextRefresh = Math.max(getRefreshTime(tgt),
              now + kerberosMinSecondsBeforeRelogin);

Most of the time nextRefresh = getRefreshTime(tgt). If it is renewing exactly on refreshTime,
and there are parallel operations using expired ticket. There is a time gap that some operations
might not perform until the next tgt is obtained. Ideally, we want to keep service uninterrupted,
therefore getNextTgtRenewalTime supposed to calculate the time a few minutes before Kerberos
tgt expired to determine the nextRefresh time. It looks like we are not using getNextTgtRenewalTime
method to calculate nextRefresh instead opt-in to use ticket expiration time as base line
for nextRefresh. I think patch 2 approach can create time gap then strain on KDC server when
ticket can not be renewed. It would be better to calculate nextRefresh based on getNextTgtRenewalTime.

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