Mark Little

(5253) Web Services and Transactions

Technical long talk 50 min

Wednesday, 2008-06-25, 16:30 - 17:20, Arena 6

Mark Little - Red Hat (speaker)

Topics

• Web services

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Abstract

The emerging world of Web Services and e-commerce places requirements on 
application developers to ensure consistency in the presence of failures 
(machine, network etc.) Without consistency guarantees, users will find it hard 
to trust services and therefore service providers will run the risk of losing 
business and reputations. In the traditional world of distributed objects, 
consistency guarantees are typically provided by transaction systems which have 
the well known ACID properties (Atomicity, Consistency, Isolation and 
Durability). However, strict ACID semantics require the use of a blocking 
protocol, such that resources acquired within the scope of such a transaction 
must remain inaccessible to others until that transaction has completed. In a 
tightly coupled environment such as a JEE intranet, where transactions are 
typically of short duration, this is not a problem. In the world of Web 
Services, where business interactions may span hours or days, ACID semantics 
become too restricting.

JBoss, IBM, Microsoft and others have been working in OASIS on the Web Services 
Transactions (WS-TX) standard which is an attempt to address these issues. It 
has set out to provide extended transaction models where ACID properties can be 
weakened in a controlled manner depending upon the requirements of the service; 
these models are often referred to as forward compensation transactions. As 
such, resources do not need to be reserved for extended periods of time, as long 
as users and applications can cope with the (hopefully rare) occurrences where 
such resources are no longer available when the transaction terminates. In 
addition, interoperability with existing ACID transaction applications and 
systems is extremely important: back-end systems may well continue to use such 
transactions to maintain internal consistency. Therefore, it is possible for a 
WS-TX transaction to glue together “islands of ACID-ity”, with non-ACID 
services; what Gartner terms multi-modal transactions.

However, how do application developers actually use these transaction models? 
How can they be tied into JEE? In this presentation we shall describe the issues 
which have lead to the development of WS-TX  and then step through the 
development of a real-world transactional Web Services application that uses 
both ACID transactions and compensation transactions.