[dna-dev] Non-XA compliant resource participation in distributed transactions

[Mark Little]

Compensating transactions do not have the same failure semantics as  
ACID transactions with LRCO (last resource commit optimisation). With  
a compensating transaction you attempt to undo, but the work has  
really been done. It may not be possible to completely reverse the  
work that was done, without running into a cascading rollback scenario  
where you are chasing all of the entities that read the "wrong data"  
to get them to undo that "read", which may not be possible at all.

There is no one size that fits all: that's why we (as a transaction  
industry) have been working on a variety of extended transaction  
models over the years. Each is aimed for a specific use case and  
offers a trade-off.

BTW, JBossTS supports compensating transactions (actually a variety of  
them) with the same underlying transaction engine.

Mark.


On 14 May 2008, at 22:18, Randall Hauch wrote:

> This is the behavior allowed by JBoss Transactions (Arjuna), and it  
> seems useful.  However, I wonder if we can do compensating  
> transactions, is there still an advantage to supporting n-1 XA plus  
> 1 non-XA?
>
> Cheers,
>
> Randall
>
> On May 14, 2008, at 4:10 PM, John P. A. Verhaeg wrote:
>
>> Seems like we ought to strive to support n-1 XA resources for  
>> distributed transactions, allowing for the last participant in a  
>> transaction (thus, this participants updates can't be done in  
>> parallel with the other resources) to not support XA transactions,  
>> but still participate in a distributed transaction with other XA- 
>> compliant resources.  Unlike compensating transactions, the non-XA  
>> participant would appear transactional and none of the updates  
>> would be visible until the entire transaction was complete.  It  
>> seems like this could open up many more possible configurations for  
>> customers.
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>
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----
Mark Little
mlittle at redhat.com

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