Title: Message
Mike,
It seems to me that how receive/reply is implemented by the
engine is an implementation detail. The BPEL language should not dictate how a
SOAP gateway interacts with a gateway.
Regarding maintenance, I think that the engine can actually
be implemented such that it goes in maintenace in a graceful fashion if it is in
the process of service synchronous requests.
Edwin
From: Marin, Mike [mailto:]
Sent: Wednesday, October 15, 2003 9:30 AM
To: Ron
Ten-Hove; Fletcher, Tony
Cc: Ugo Corda; bpel
implementation
Subject: RE: [wsbpel-implement] Fault tolerance
considerations
Edwin’s
suggestion does make sense; but note that this is not only an “error recovery”
issue. This arises during normal operation. Let assume that your engine handle
thousands of processes per hour, and so at any given moment, some of those
processes will be in between the receive/reply pair. How do you bring the
engine down for maintenance (let say hardware upgrade or database backup)?
The
act of bringing the engine down will certainly stop some of the processes in
the middle of the receive/reply pair. Most engines will consider shutting down
the engine as a normal operation, and they will keep the state of all the
running processes, but in this case you are forced into considering it as an
abnormal operation for those processes that are in the receive/reply pair.
Again,
IMHO receive/reply should be asynchronous. They can be seen as synchronous
from a invoke perspective, but unless is implemented as asynchronous it
creates unnecessary issues for the
implementer.
AUTOTEXTLIST
\s "E-mail Signature" --
Regards,
Mike
Marin
-----Original
Message-----
From: Ron
Ten-Hove [mailto:]
Sent: Wednesday, October 15, 2003 8:28
AM
To: Fletcher,
Tony
Cc: Ugo Corda; Marin,
Mike; bpel implementation
Subject: Re: [wsbpel-implement] Fault
tolerance considerations
Tony,
Fletcher, Tony
wrote:
Dear Ron, Mike, Ugo,
and others,
Is this problem not
occurring because of layer violation. Surely BPEL - and BPEL
implementations - should not need to worry beyond setting a timeout at the
sending side on an invoke to which a reply is expected. At the BPEL
should just a hand a message over to the SOAP HTTP implementation, and receive
messages back from it. Exactly how the message is sent (and in
particular whether the response rides on an HTTP response or request is surely
not a BPEL concern (???)
I think the issue arises only
in error cases, where error recovery/handling may need some extra insight into
the lower-level binding characteristics. As Edwin has suggested, this can be
determined at deployment time, along with suitable recovery policies.
Obviously this sort of thing is implementation-specific, but Edwin's approach
makes a lot of sense.
-Ron
