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From "Hadoop QA (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-2958) RMStateStore seems to unnecessarily and wronly store sequence number separately
Date Thu, 25 Dec 2014 22:49:15 GMT

    [ https://issues.apache.org/jira/browse/YARN-2958?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14258866#comment-14258866
] 

Hadoop QA commented on YARN-2958:
---------------------------------

{color:red}-1 overall{color}.  Here are the results of testing the latest attachment 
  http://issues.apache.org/jira/secure/attachment/12689131/YARN-2958.001.patch
  against trunk revision a164ce2.

    {color:green}+1 @author{color}.  The patch does not contain any @author tags.

    {color:red}-1 tests included{color}.  The patch doesn't appear to include any new or modified
tests.
                        Please justify why no new tests are needed for this patch.
                        Also please list what manual steps were performed to verify this patch.

    {color:green}+1 javac{color}.  The applied patch does not increase the total number of
javac compiler warnings.

    {color:green}+1 javadoc{color}.  There were no new javadoc warning messages.

    {color:green}+1 eclipse:eclipse{color}.  The patch built with eclipse:eclipse.

    {color:red}-1 findbugs{color}.  The patch appears to introduce 15 new Findbugs (version
2.0.3) warnings.

    {color:green}+1 release audit{color}.  The applied patch does not increase the total number
of release audit warnings.

    {color:red}-1 core tests{color}.  The patch failed these unit tests in hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager:

                  org.apache.hadoop.yarn.server.resourcemanager.recovery.TestZKRMStateStore

Test results: https://builds.apache.org/job/PreCommit-YARN-Build/6190//testReport/
Findbugs warnings: https://builds.apache.org/job/PreCommit-YARN-Build/6190//artifact/patchprocess/newPatchFindbugsWarningshadoop-yarn-server-resourcemanager.html
Console output: https://builds.apache.org/job/PreCommit-YARN-Build/6190//console

This message is automatically generated.

> RMStateStore seems to unnecessarily and wronly store sequence number separately
> -------------------------------------------------------------------------------
>
>                 Key: YARN-2958
>                 URL: https://issues.apache.org/jira/browse/YARN-2958
>             Project: Hadoop YARN
>          Issue Type: Bug
>          Components: resourcemanager
>            Reporter: Zhijie Shen
>            Assignee: Varun Saxena
>            Priority: Blocker
>         Attachments: YARN-2958.001.patch
>
>
> It seems that RMStateStore updates last sequence number when storing or updating each
individual DT, to recover the latest sequence number when RM restarting.
> First, the current logic seems to be problematic:
> {code}
>   public synchronized void updateRMDelegationTokenAndSequenceNumber(
>       RMDelegationTokenIdentifier rmDTIdentifier, Long renewDate,
>       int latestSequenceNumber) {
>     if(isFencedState()) {
>       LOG.info("State store is in Fenced state. Can't update RM Delegation Token.");
>       return;
>     }
>     try {
>       updateRMDelegationTokenAndSequenceNumberInternal(rmDTIdentifier, renewDate,
>           latestSequenceNumber);
>     } catch (Exception e) {
>       notifyStoreOperationFailed(e);
>     }
>   }
> {code}
> {code}
>   @Override
>   protected void updateStoredToken(RMDelegationTokenIdentifier id,
>       long renewDate) {
>     try {
>       LOG.info("updating RMDelegation token with sequence number: "
>           + id.getSequenceNumber());
>       rmContext.getStateStore().updateRMDelegationTokenAndSequenceNumber(id,
>         renewDate, id.getSequenceNumber());
>     } catch (Exception e) {
>       LOG.error("Error in updating persisted RMDelegationToken with sequence number:
"
>             + id.getSequenceNumber());
>       ExitUtil.terminate(1, e);
>     }
>   }
> {code}
> According to code above, even when renewing a DT, the last sequence number is updated
in the store, which is wrong. For example, we have the following sequence:
> 1. Get DT 1 (seq = 1)
> 2. Get DT 2( seq = 2)
> 3. Renew DT 1 (seq = 1)
> 4. Restart RM
> The stored and then recovered last sequence number is 1. It makes the next created DT
after RM restarting will conflict with DT 2 on sequence num.
> Second, the aforementioned bug doesn't happen actually, because the recovered last sequence
num has been overwritten at by the correctly one.
> {code}
>   public void recover(RMState rmState) throws Exception {
>     LOG.info("recovering RMDelegationTokenSecretManager.");
>     // recover RMDTMasterKeys
>     for (DelegationKey dtKey : rmState.getRMDTSecretManagerState()
>       .getMasterKeyState()) {
>       addKey(dtKey);
>     }
>     // recover RMDelegationTokens
>     Map<RMDelegationTokenIdentifier, Long> rmDelegationTokens =
>         rmState.getRMDTSecretManagerState().getTokenState();
>     this.delegationTokenSequenceNumber =
>         rmState.getRMDTSecretManagerState().getDTSequenceNumber();
>     for (Map.Entry<RMDelegationTokenIdentifier, Long> entry : rmDelegationTokens
>       .entrySet()) {
>       addPersistedDelegationToken(entry.getKey(), entry.getValue());
>     }
>   }
> {code}
> The code above recovers delegationTokenSequenceNumber by reading the last sequence number
in the store. It could be wrong. Fortunately, delegationTokenSequenceNumber updates it to
the right number.
> {code}
>     if (identifier.getSequenceNumber() > getDelegationTokenSeqNum()) {
>       setDelegationTokenSeqNum(identifier.getSequenceNumber());
>     }
> {code}
> All the stored identifiers will be gone through, and delegationTokenSequenceNumber will
be set to the largest sequence number among these identifiers. Therefore, new DT will be assigned
a sequence number which is always larger than that of all the recovered DT.
> To sum up, two negatives make a positive, but it's good to fix the issue. Please let
me know if I've missed something here.



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