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From Kim van der Riet <kim.vdr...@redhat.com>
Subject Re: Question on the role of the TPL in the message store
Date Thu, 01 Oct 2009 12:51:01 GMT
On Wed, 2009-09-30 at 16:46 -0400, Steve Huston wrote:
> I've been studying the Red Hat message store code and, in particular
> this week, the transaction handling and TPL. From what I understand at
> this point, the role of the TPL is to enable recover prepared but not
> committed transaction actions. And, this is mostly needed because the
> journal is not transactional. Is this correct?

Correct - the TPL simply records the transaction boundaries for recovery
- something that is usually internal to traditional databases. The
previous BDB version used BDB's internal transactions to provide this
capability to the store.

> If this is correct, and I am looking primarily at providing an
> SQL-backed store for Windows (at least right now), I don't really need
> to worry about the TPL stuff (yet) since SQL transactions don't
> require an external assist in the form of the TPL.
> If I use two layers of transaction, one around the 2PC prepare/commit
> sequence, and others around the individual enqueue/dequeue ops, that
> would do it, I think. Does this make sense?

Sounds good. Make sure that the multi-queue cases are handled correctly,
ie a transaction that spans one or more messages being enqueued and/or
dequeud on multiple queues.

> Thanks,
> -Steve

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