Re: verbatim notes from London bt models meeting

[Peter Furniss <peter.furniss@choreology.com>]

This was going to be my comments to Sazi on his clarifications, but since
I've now circulated those notes, it's probably better to discuss this here.

I think there is a bit of a difference of thought and it's worth sorting
out.

We were considering that the recipient side could *choose* to implement its
part in the action as if it were an ACID transaction - e.g. would directly
use its transaction service, treating the cohesion as the superior, and
using a regular XA database to hold the data. The termination/commit/cancel
message of the cohesion/business transaction is mapped to the xa_commit.  If
it does this, obviously it does make the data subject to locks, but
essentially, it owns the data and it can decide whether this is acceptable,
even for a longer time than is normally considered acceptable.

Meanwhile, another service in the same cohesion might *choose* to implement
using a complete-now-but-allow-for-compensation approach. In this case, it
might make the initial application of the operation a proper transaction,
and the compensation (if it happens), another transaction.

The mechanisms used would be considered internal to the service. But those
in London wanted the first to be possible.

I think this effectively means we are looking at a two-phase exchange (I
think this was the assumption of those physically at the meeting, though I
don't remember it being stated quite that directly). But a two-phase
exchange (meaning just "can you do your part ?", "yes", "then let it be
done"/"dont do it after all") is inevitable if we are to have any level of
atomicity or consistent application of operations anyway.

[ In fact, it seems to me there is an implicit two-phase exchange in the
original BEA submission, but the equivalent of the vote is carried in the
application replies, with the prepare implicit in the message itself.
Without this assumption, there is no way the initiator + main coordinator
side to know what is being committed. }



Separately - most of the timelimits discussion was on the possibility of the
compensation itself having a limit, as in reservation situations, where the
reservation is held for some period and then service will decide for you if
you haven't got back to them.  I don't think this can be avoided - it's just
the way some people will do business.  If the timeout is hit, then it does
rather break the model (it's similar to heuristic decisions, but at least
there can be prior warning in this case).

We definitely did not come to final conclusions on timeouts.



Peter

> -----Original Message-----
> From: Sazi Temel [mailto:sazi.temel@bea.com]
> Sent: 05 April 2001 04:26
> To: Peter Furniss
> Subject: RE: bt models london minutes/notes
>
>
>
> Including again.. just tried to clarify a few comments I have made during
> the meeting, if you still do not get the attachment, no problem. I am sure
> I will get another chance!
>
> --Sazi
>
> At 01:08 AM 4/5/01 +0100, you wrote:
> >Sazi,
> >
> >No attachment arrived at me - I just saw the statement that it had been
> >converted (as below).
> >
> >Your message crossed with the reworked summary I sent out, in
> which I tried
> >to summarise what I thought was the consensus. I'm sure you'll
> say if it is
> >still wrong.
> >
> >Mark - what shall we do with the detailed notes ?
> >
> >Peter
> >
> >
> >> -----Original Message-----
> >> From: Sazi Temel [mailto:sazi.temel@bea.com]
> >> Sent: 04 April 2001 21:18
> >> To: Peter Furniss; Little Mark
> >> Subject: Re: bt models london minutes/notes
> >>
> >>
> >>
> >> Peter,
> >> Included a modified version of the doc that you have sent -I just
> >> clarified
> >> what I said during the meeting (see marked >>> text in the
> doc). Thanks.
> >>
> >> --Sazi
> >>
> >> At 06:28 PM 4/3/01 +0100, Peter Furniss wrote:
> >> >This is what I typed during the meeting. Please comment (cc
> >> Mark) if I have
> >> >traduced or misrepresented you. I tended not to include
> things when I was
> >> >directly involved.
> >> >
> >> >
> >> >Peter
> >> >
> >> >
> >> >------------------------------------------------
> >> >Peter Furniss
> >> >Choreology Ltd
> >> >
> >> >email:  peter.furniss@choreology.com
> >> >phone:  +44 20 7670 1679
> >> >direct: +44 20 7670 1783
> >> >13 Austin Friars, London EC2N 2JX
> >> >
> >> >Attachment Converted:
> "c:\data\email\attach\London_april_minutes_am.doc"
> >> >
> >>
> >
> >
> >