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https://issues.apache.org/jira/browse/OOZIE-2854?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15957289#comment-15957289
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Steven Hancz commented on OOZIE-2854:
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Peter,
I am glad that you found this issue. I just built two labs to test an HA
solution for cluster metadata storage. It makes no sense to have a hadoop
cluster and a single MySQL failure will bring it down.
So far I build a Galera MySQL cluster and Galera MariaDB cluster but I have not
pointed hadoop to it just imported the data. NDB clustering will not work as it
does not uses the InnoDB engine and the import will fail.
I also have a case opened with Cloudera on this matter that I am waiting on.
Galera cluster states that it is synchronous
https://mariadb.com/kb/en/mariadb/about-galera-replication/
but your findings are different.
All I want to do is to have a metadata storage that is not prone to a single
point of failure. Have you run similar test with Oracle RAC?
Steven
> Oozie should handle transient DB problems
> -----------------------------------------
>
> Key: OOZIE-2854
> URL: https://issues.apache.org/jira/browse/OOZIE-2854
> Project: Oozie
> Issue Type: Improvement
> Components: core
> Reporter: Peter Bacsko
> Assignee: Peter Bacsko
>
> There can be problems when Oozie cannot update the database properly.
> Recently, we have experienced erratic behavior with two setups:
> * MySQL with the Galera cluster manager. Galera uses cluster-wide optimistic
> locking which might cause a transaction to rollback if there are two or more
> parallel transaction running and one of them cannot complete because of a
> conflict.
> * MySQL with Percona XtraDB Cluster. If one of the MySQL instances is killed,
> Oozie might get "Communications link failure" exception during the failover.
> The problem is that failed DB transactions later might cause a workflow
> (which are started/re-started by RecoveryService) to get stuck. It's not
> clear to us how this happens but it has to do with the fact that certain DB
> updates are not executed.
> The solution is to use some sort of retry logic with exponential backoff if
> the DB update fails. We could start with a 100ms wait time which is doubled
> at every retry. The operation can be considered a failure if it still fails
> after 10 attempts. These values could be configurable. We should discuss
> initial values in the scope of this JIRA.
> Note that this solution is to handle *transient* failures. If the DB is down
> for a longer period of time, we have to accept that the internal state of
> Oozie is corrupted.
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