Issue - 52 - Deadlocks and Internal Messaging

["Yaron Goland" <ygoland@bea.com>]

Satish, 
    I'm not 100% sure what you mean when you say that internal messaging
causes deadlock. One of my basic assumptions is that any messaging operation
that does not complete within a certain period of time will eventually time
out. So I'm not clear on how internal messaging could cause deadlocks.
 
What I can see is how one could create a livelock. For example:
 
<flow>
   <sequence>
      <while condition="bpws:getVariableData(Success1) <> "done">
         <scope>
            <faultHandlers>
               <catch faultName="ProprietaryTimeOutFault"><empty/></catch>
            </faultHandlers>
            <sequence>
               <invoke partnerLink="TalkingToSelf" operation="getFoo"
inputVariable="FooIn" outputVariable="FooOut">
               <assign><copy><from>Done</from><to
variable="Success1"/></copy></assign>
            </sequence>
         </scope>
      </while>
      <!-- Wait to receive a getBar incoming message and then do useful work
-->
   </sequence>
   <sequence>
      <while condition="bpws:getVariableData(Success2) <> "done">
         <scope>
            <faultHandlers>
               <catch faultName="ProprietaryTimeOutFault"><empty/></catch>
            </faultHandlers>
            <sequence>
               <invoke partnerLink="TalkingToSelf" operation="getBar"
inputVariable="BarIn" outputVariable="BarOut">
               <assign><copy><from>Done</from><to
variable="Success2"/></copy></assign>
            </sequence>
         </scope>
      </while>
      <!-- Wait to receive a getFoo incoming message and then do useful work
-->
   </sequence>
</flow>
 
Is this what you meant when you aid deadlock?
 
    Yaron
 

-----Original Message-----
From: Satish Thatte [mailto:satisht@microsoft.com]
Sent: Thursday, September 25, 2003 9:24 PM
To: ygoland@bea.com; wsbpel@lists.oasis-open.org
Subject: RE: [wsbpel] Issue - 67 - Clarify semantics of serializable scopes



Yaron,

 

Perhaps I misspoke.  I thought in the context of the discussion on Issue#52,
you had commented that deadlocks are already possible in BPEL 1.1, in
response to my claim that internal messaging would introduce them for the
first time.

 

My apologies if I mistakenly interpreted that to mean serializable scopes in
BPEL 1.1 already allow deadlocks because of the locking they imply.

 

Satish

 

 


  _____  


From: Yaron Goland [mailto:ygoland@bea.com] 
Sent: Wednesday, September 24, 2003 3:44 PM
To: wsbpel@lists.oasis-open.org
Subject: RE: [wsbpel] Issue - 67 - Clarify semantics of serializable scopes

 

I'm not sure what the issue is referring to vis a vis any comments I made.
I'm not aware of serializable scopes introducing any new deadlock issues
that aren't already in BPEL [1]. After all Serializable scopes are really
nothing more than instructions to the thread scheduler. So in theory any
behavior you could see as a result of a serializable scope could be
reproduced by a sufficiently eccentric thread scheduler.

 

    Yaron

 

[1] The use of serializable scopes and links could cause deadlocks. But the
authors understood this and so explicitly banned the use of links that cross
serialized boundaries in section 12.5.

         

-----Original Message-----
From: ws-bpel issues list editor [mailto:peter.furniss@choreology.com]
Sent: Wednesday, September 24, 2003 1:28 AM
To: wsbpel@lists.oasis-open.org
Subject: [wsbpel] Issue - 67 - Clarify semantics of serializable scopes

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Issue - 67 - Clarify semantics of serializable scopes


Status: open
Categories: concurrency control 
Date added: 24 Sep 2003
Submitter: Satish Thatte <mailto:satisht@microsoft.com> 
Date submitted: 23 September 2003
Champion: Satish Thatte <mailto:satisht@microsoft.com> 
Document: Language specification, section 13.6 
Description: There has been some recent discussion regarding the concurrency
control semantics of serializable scopes. Yaron Goland had also raised a
question regarding the possibility of deadlock among serializable scopes.
This section needs additional wording to clarify these issues. 
Links: Ron
<http://lists.oasis-open.org/archives/wsbpel/200309/msg00169.html> Ten-Hove,
15 Sep 2003
Changes: 24 Sep 2003 - new issue


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