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From "Daniel Templeton (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-7262) Add a hierarchy into the ZKRMStateStore for delegation token znodes to prevent jute buffer overflow
Date Wed, 04 Oct 2017 14:42:00 GMT

    [ https://issues.apache.org/jira/browse/YARN-7262?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16191351#comment-16191351

Daniel Templeton commented on YARN-7262:

My comments after a closer look:
# The new property and default should have javadocs
# Please don't you start with the {{null != x}} stuff, too...  \*sigh\*
# Please add assert messages, and let's not mix {{assertX()}} with {{Assert.assertX()}} calls.
# I feet like you should test with more than just a split index of 0 or 1.
# You don't need to store {{token3}} in {{testDelegationTokenNodeWithSplitChangeAcrossRestarts()}}.
# In {{initInternal()}}. shouldn't you consider 0 a valid split index?
# "Unknown child node with name: " could be a bit more descriptive.  Child of what?  What
caused it?  What should the admin do about it?  Same for the messages in {{checkRemoveParentZnode()}}
# In {{loadDelegationTokenFromNode()}}, can I get an _else_ instead of an early return?
# I don't like reassigning the {{splitIdx}} parameter in {{getLeafZnodePath()}}.
# May as well split the long line on the equals in {{RMStateStore}}.

I still want to take a closer look at the ZK code, but I need more sleep first.

> Add a hierarchy into the ZKRMStateStore for delegation token znodes to prevent jute buffer
> ---------------------------------------------------------------------------------------------------
>                 Key: YARN-7262
>                 URL: https://issues.apache.org/jira/browse/YARN-7262
>             Project: Hadoop YARN
>          Issue Type: Improvement
>    Affects Versions: 2.6.0
>            Reporter: Robert Kanter
>            Assignee: Robert Kanter
>         Attachments: YARN-7262.001.patch
> We've seen users who are running into a problem where the RM is storing so many delegation
tokens in the {{ZKRMStateStore}} that the _listing_ of those znodes is higher than the jute
buffer. This is fine during operations, but becomes a problem on a fail over because the RM
will try to read in all of the token znodes (i.e. call {{getChildren}} on the parent znode).
 This is particularly bad because everything appears to be okay, but then if a failover occurs
you end up with no active RMs.
> There was a similar problem with the Yarn application data that was fixed in YARN-2962
by adding a (configurable) hierarchy of znodes so the RM could pull subchildren without overflowing
the jute buffer (though it's off by default).
> We should add a hierarchy similar to that of YARN-2962, but for the delegation token

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