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Subject: Re: [wsbpel] Issue 135 - Proposal to vote
Satish Thatte wrote: > Alex, > > > > I agree with 2 and it would be best if we ensure this by saying that > the terminationHandler is invoked after terminating all nested > activities and uninstalling all fault handlers. This will have the > intended effect. > > > > As I wrote separately in response to Assaf, the intention was indeed > to have the completionHandler run after terminating all nested > activities in the prematurely terminated scope. > > > > I do not think we should have a terminationHandler at the process > level because, as I wrote in response to Danny below, we have no > mechanism to cause it to be invoked. To quote from that thread > > > > No, the fact that the process does not have a termination handler is > > deliberate since we do not have a notion of forced termination of a > > process instance. I deliberately moved <terminate/> to <exit/> to make > > that clear. > Although we do not specify such a mechanism, we cannot ignore that implementations may choose to offer it, and the possibility of a best practice that relies on using a scope as the main activity of the process to handle this event. I question if it would not make more sense to normalize it as part of the process definition. Assaf > > > > Satish > > > > ------------------------------------------------------------------------ > > *From:* Alex Yiu [mailto:alex.yiu@oracle.com] > *Sent:* Monday, September 27, 2004 7:34 PM > *To:* Assaf Arkin > *Cc:* Satish Thatte; Danny van der Rijn; wsbpel@lists.oasis-open.org; > Alex Yiu > *Subject:* Re: [wsbpel] Issue 135 - Proposal to vote > > > > > Hi, > > (1) > I guess this is more like a "completionHandler" discussion, not > exactly Issue 135. :-) > Assaf, thanks for your insight. I can see your point. > It would be much easier for people to program a completionHandler, if > we define the completionHandler is invoked AFTER the termination of > all nested concurrent activities. Then, I guess it is safe to say the > BPEL engine should not try to terminate an already terminated activity. > > (2) > Anyhow, for Issue 135, I believe we need to say (at least) for > external termination/cancellation : The second or subsequent attempt > to forcibly terminate a scope will be ignored. The terminationHandler > (if still running) invoked by the first attempt will be allowed to > continue. The terminationHandler will NOT be invoked more than once. > > (3) > One more catch / clarification is: do we want to add > "terminationHandler" to the process level also, besides scope level? I > tend to say yes. > > > Thanks! > > > Regards, > Alex Yiu > > > Assaf Arkin wrote: > > Satish Thatte wrote: > > > It is not necessarily true that a scope will be forced to terminate > only once. If we do premature completion with a completion handler > then a fault in the completion handler may cause an attempt to > forcibly terminate a scope more than once. > > I'm having a problem understanding this sentence. > > Do you mean that completion of a scope entails forceful termination of > that scope, and so it can be terminated multiple times, once from the > complete activity and once from the fault? My understanding was that > completion of a scope is separate from termination, completion of a > scope may entail termination of nested scopes. > > Or, could the completion handler be invoked in the scope while nested > scopes are still performing some work (e.g. their termination handlers > are still in progress)? It would be hard to define a completion > handler for a scope not knowing that its invocation occurs after all > other work in the scope has completed. > > Assaf > > > > > ------------------------------------------------------------------------ > > *From:* Alex Yiu [mailto:alex.yiu@oracle.com] > *Sent:* Monday, September 27, 2004 2:33 PM > *To:* Satish Thatte > *Cc:* Danny van der Rijn; wsbpel@lists.oasis-open.org > <mailto:wsbpel@lists.oasis-open.org>; Alex Yiu > *Subject:* Re: [wsbpel] Issue 135 - Proposal to vote > > > > > Hi, > > +1 to Satish's proposal. > > Just want to suggest a couple of minor things to add explicitly to the > spec for clarity > > * A forced termination is an abnormal termination of a scope. The > compensation handler of a scope will not be installed after a > forced termination. (To distinguish the terminationHandler from > the potental completionHandler) > * From the text from other parts of the existing spec, I can infer > that there is NO such a situation that a BPEL engine will try to > terminate a scope more than once due to internal conditions. > Could someone confirm my inference? > On the other hand, it may be possible that people may try to > "terminate" a process gracefully from a BPEL managment tool more > than once, instead of "kill" it immediately? > > Do we want to make this explicitly by saying the second or > subsequent attempt to terminate an activity / a scope which is > being terminated will be ignored? Hence, the terminationHandler > of a particular scope instance will NOT be invoked more than once. > > > A side suggestion: it would be nice to have finite state diagram to > illustrate the state transition of a scope in the spec, especially > after we pass both completionHandler and terminationHandler issue. The > life cycle of a scope can be complicated. > > > Thanks! > > > Regards, > Alex Yiu > > > Satish Thatte wrote: > > thanks > > > > ------------------------------------------------------------------------ > > *From:* Danny van der Rijn [mailto:dannyv@tibco.com] > *Sent:* Friday, September 24, 2004 12:15 PM > *To:* Satish Thatte > *Cc:* wsbpel@lists.oasis-open.org <mailto:wsbpel@lists.oasis-open.org> > <mailto:wsbpel@lists.oasis-open.org> > *Subject:* Re: [wsbpel] Issue 135 - Proposal to vote > > > > i misinterpreted some subleties in the proposal. i withdraw my comments. > > Satish Thatte wrote: > > ?? > > > > The forcedTermination fault handler was able to do compensation. Why is > > this a change? > > > > No, the fact that the process does not have a termination handler is > > deliberate since we do not have a notion of forced termination of a > > process instance. I deliberately moved <terminate/> to <exit/> to make > > that clear. > > > > This proposal actually changes absolutely nothing semantically. It > > simply changes syntax. > > > > -----Original Message----- > > From: Danny van der Rijn [mailto:dannyv@tibco.com] > Sent: Friday, September 24, 2004 8:31 AM > > To: Satish Thatte > > Cc: wsbpel@lists.oasis-open.org <mailto:wsbpel@lists.oasis-open.org> > <mailto:wsbpel@lists.oasis-open.org> > > Subject: Re: [wsbpel] Issue 135 - Proposal to vote > > > > i don't like the idea of the default termination handler performing > compensation. this part is an addition, rather than a syntactic > substitution, and i think it falls on the wrong side of the meaning of > default. > > > > also, i assume that the fact that a process doesn't have a termination > handler is an inadvertent omission? > > > > danny > > > > Satish Thatte wrote: > > > > > > > Overview: > > > > > > > > The bpws:forcedTermination "fault" in the current specification is not > > > > a normal fault. It is simply a way to permit interception of forced > > termination by a scope to perform special handling to shut the scope > > down in an orderly manner. The differences from a normal fault include > > the inability to be caught by a catchAll handler, and the inability to > > throw or rethrow any fault within the handler. It is thus proposed that > > we eliminate the notion of a bpws:forcedTermination fault from the > > specification and replace it with a notion of a special handler for > > forced termination. A secondary part of the proposal is to replace the > > <terminate/> activity with an <exit/> activity with identical semantics, > > simply to avoid terminological confusion with the notion of forced > > termination. > > > > > > > > > Detailed proposal: > > > > > > > > In all the text of the specification, including section 5 and Appendix > > > > A, eliminate the mention of bpws:forcedTermination and remove this token > > from the bpws namespace. > > > > > > > > > In Sections 6.2 and 13 > > > > > > > > Replace the syntax > > > > > > > > <scope variableAccessSerializable="yes|no" standard-attributes> > > > > standard-elements > > > > <variables>? > > > > ... > > > > </variables> > > > > <correlationSets>? > > > > ... > > > > </correlationSets> > > > > <faultHandlers>? > > > > ... > > > > </faultHandlers> > > > > <compensationHandler>? > > > > ... > > > > </compensationHandler> > > > > <eventHandlers>? > > > > ... > > > > </eventHandlers> > > > > activity > > > > </scope> > > > > > > > > with the syntax > > > > > > > > <scope variableAccessSerializable="yes|no" standard-attributes> > > > > standard-elements > > > > <variables>? > > > > ... > > > > </variables> > > > > <correlationSets>? > > > > ... > > > > </correlationSets> > > > > <faultHandlers>? > > > > ... > > > > </faultHandlers> > > > > <compensationHandler>? > > > > ... > > > > </compensationHandler> > > > > <terminationHandler>? > > > > ... > > > > </terminationHandler> > > > > <eventHandlers>? > > > > ... > > > > </eventHandlers> > > > > activity > > > > </scope> > > > > > > > > In Section 13.4.2 > > > > > > > > Replace the text > > > > > > > > Scopes provide the ability to control the semantics of forced > > > > termination to some degree. When the activity being terminated is in > > fact a scope, the behavior of the scope is interrupted and the fault > > handler for the standard bpws:forcedTermination fault is run. Note that > > this applies only if the scope is in normal processing mode. If the > > scope has already experienced an internal fault and invoked a fault > > handler, then as stated above, all other fault handlers including the > > handler for bpws:forcedTermination are uninstalled, and the forced > > termination has no effect. The already active fault handler is allowed > > to complete. > > > > > > > > The fault handler for the bpws:forcedTermination fault is designed like > > > > other fault handlers, but this fault handler cannot rethrow any fault. > > Even if an uncaught fault occurs during its behavior, it is not rethrown > > to the next enclosing scope. This is because the enclosing scope has > > already faulted, which is what is causing the forced termination of the > > nested scope. > > > > > > > > In other respects this is a normal fault handler. Its behavior begins > > > > by implicitly (recursively) terminating all activities directly enclosed > > within its associated scope that are currently active. It can invoke > > compensate activities. And when it is missing, it is provided by using > > the same implicit behavior that is used for all other implicit fault > > handlers. > > > > > > > > Note that forced termination of nested scopes occurs in innermost-first > > > > order as a result of the rule (quoted above) that the behavior of any > > fault handler begins by implicitly (recursively) terminating all > > activities directly enclosed within its associated scope that are > > currently active. > > > > > > > > with the text > > > > > > > > Scopes provide the ability to control the semantics of forced > > > > termination to some degree. When the activity being terminated is in > > fact a scope, the forced termination of a scope begins by terminating > > all activities directly enclosed within its associated scope that are > > currently active. Following this, the custom termination handler for > > the scope, if present, is run. If the custom termination handler is > > missing, the default termination handler performs compensation of all > > successfully completed nested scopes in the same order as in the case of > > a default fault handler. > > > > > > > > Forced termination for a scope applies only if the scope is in normal > > > > processing mode. If the scope has already experienced an internal fault > > and invoked a fault handler, then the termination handler is > > uninstalled, and the forced termination has no effect. The already > > active fault handler is allowed to complete. > > > > > > > > The termination handler for a scope is permitted to use the same range > > > > of activities as a fault handler, including the <compensate/> activity. > > However, a termination handler cannot throw any fault. Even if an > > uncaught fault occurs during its behavior, it is not rethrown to the > > next enclosing scope. This is because the enclosing scope has already > > either faulted or is in the process of being terminated, which is what > > is causing the forced termination of the nested scope. > > > > > > > > Forced termination of nested scopes occurs in innermost-first order as > > > > a result of the rule (stated above) that the termination handler is run > > after terminating all activities (including scope activities) directly > > enclosed within its associated scope that are currently active. > > > > > > > > > > To unsubscribe from this mailing list (and be removed from the roster > > > > of the OASIS TC), go to > > http://www.oasis-open.org/apps/org/workgroup/wsbpel/members/leave_workgr > > oup.php. > > > > > > > > > > > > > > > > > To unsubscribe from this mailing list (and be removed from the roster > of the OASIS TC), go to > http://www.oasis-open.org/apps/org/workgroup/wsbpel/members/leave_workgroup.php. > > > > > > > > > To unsubscribe from this mailing list (and be removed from the roster > of the OASIS TC), go to > http://www.oasis-open.org/apps/org/workgroup/wsbpel/members/leave_workgroup.php. > > > > > > > > -- "Those who can, do; those who can't, make screenshots" ---------------------------------------------------------------------- Assaf Arkin arkin@intalio.com Intalio Inc. www.intalio.com The Business Process Management Company (650) 577 4700 This message is intended only for the use of the Addressee and may contain information that is PRIVILEGED and CONFIDENTIAL. 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