On Sun, Apr 13, 2008 at 7:50 PM, Maarten <[EMAIL PROTECTED]> wrote:
>
>  I have an update on this issue. It seems that the problems that we
>  have seen were caused by the fact that two mongrel instances were
>  used, each with their own caching engine. Since the process expression
>  caches were not synchronized, the OpenWFE processes sometimes jumped
>  back or forth causing very weird behaviour. I tested on another system
>  with a single mongrel instance, and there it run without problems.
>  Does anyone have successfully used OpenWFE on a system with multiple
>  mongrel instances?

Hello Maarten,

This question reminds me of this one :
http://groups.google.com/group/openwferu-users/browse_thread/thread/ce84da80c6f2ff2

In that case it might be better to put the workflow engine instance
out of the rails application, the suggestion being to use single
restful instance outside of the "front" rails application (like you
have a single db outside of the rails app, usually).

I don't know if you are using ThreadedDbExpressionStorage or its
parent class DbExpressionStorage. The first one caches expressions in
memory for quicker reads and queues update requests for snappier
writes. The second one just does the read / write immediately and
returns when such an operation is done. The second one
(DbExpressionStorage) could be OK with multiple mongrels, but it's way
slower than the first one, I don't know about the kind of business
processes you are running but this "slowness" might be unacceptable
for you.

There could be interesting paths to explore, maybe using a shared
memcache for the ThreadedDbExpressionStorage or things like this. This
technique would also be valuable for expressions persisted in the
filesystem instead of the DB. (I'm personally not a fan of db
persisted expressions, I think it's OK to have workitems stored in the
db for quick lookup, but expressions storage being rather
hierarchical, a relational db is overkill, but granted : some admins
might prefer to have everything in a db).


Best regards,

-- 
John Mettraux -///- http://jmettraux.openwfe.org

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