[jira] [Commented] (OFBIZ-2353) SequenceUtil may generate duplicate IDs in Load Balancing mode

["Jacques Le Roux (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/OFBIZ-2353?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14117465#comment-14117465 ] 

Jacques Le Roux commented on OFBIZ-2353:
----------------------------------------

[~jacopoc]I also agree the code looks much better and, after reading a bit more about it, I agree SELECT FOR UPDATE was not an optimal solution (in this case with few chances of collisions optimist locking is faster than pessimist locking). While reviewing I also liked how you commented enough but not much, thanks!
I have a question:
# {code}
    if (stmt.executeUpdate(updateForLockStatement) <= 0) {
        // This should never happen
        throw new GenericEntityException("No rows changed when trying insert new sequence row with this SQL: " + sql);
    }
{code}
Why this should never happen? What if another machine/thread has just locked the tuple before the current machine/thread? Can this never happens? If yes, why? Else, why not retrying a couple of times (parametrized) then?

[~adrianc@hlmksw.com] You suggested "UPDATE... WHERE...", could you show us the code you have in mind (even roughly)?

Did I write too much?

> SequenceUtil  may generate duplicate IDs in Load Balancing mode
> ---------------------------------------------------------------
>
>                 Key: OFBIZ-2353
>                 URL: https://issues.apache.org/jira/browse/OFBIZ-2353
>             Project: OFBiz
>          Issue Type: Bug
>          Components: framework
>    Affects Versions: Release Branch 4.0, Release Branch 09.04, Trunk
>            Reporter: Philippe Mouawad
>            Assignee: Jacopo Cappellato
>            Priority: Critical
>             Fix For: Release Branch 10.04, Upcoming Branch
>
>         Attachments: OFBIZ-2353 SELECT FOR UPDATE solution.patch, OFBIZ-2353 SELECT FOR UPDATE solution.patch
>
>
> If Ofbiz is deploy on 2 servers in Load Balancing Mode
> SequenceUtil will generate duplicate IDs because synchronization is done at JVM level instead of doing it in DB.
> A good replacement implementation would be:
> org.hibernate.id.enhanced.TableGenerator
> But it would involve a dependency on Hibernate
> Philippe
> www.ubik-ingenierie.com



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