I’m working on a real time application implemented using in a SOA-style (read loosely coupled components connected via some messaging protocol – JMS, MQ or HTTP).
The architect who designed this system opted to use JMS to connect the components. This system is real time so there no need to queue up messages should one component fail (the transaction will simply time out). Further, there is no need for guaranteed delivery or rollback.
In this instance, is there any benefit to using JMS over something like an HTTP web service (speed, resource footprint, etc)?
One thing that I’m thinking is since the JMS approach requires us to set a thread pool size (the number of components listening to a JMS topic/queue), wouldn’t a HTTP service be a better fit since this additional configuration is not needed (a new thread is created for each HTTP request making the application scalable to an ‘unlimited’ number of requests until the server runs out of resources).
Am I missing something?
I don’t disagree with the points made by S.Lott at all, but here are a couple of points to consider regarding HTTP web services:
Your clients only need to know how to communicate via HTTP – a protocol well supported by just about every modern langauge in one form or another. JMS, though popular, is more specialist than HTTP, and so restricts the languages your interconnected systems can use. Perhaps not an issue for your system at the moment, but will you need to plug in other systems later that might struggle to support JMS connectivity?
Standards like WSDL and SOAP which you could levarage for your services are well supported by many langauges and there are plenty of tools around that will generate code to implement both ends of the pipeline (client and server) for you from a WSDL file, reducing the amount of dev you’ll have to do. These standards also make it relatively simple to define and publish the specification of the data you’ll be passing between your systems, something you’ll presumably have to do by hand using a queueing technology like JMS.
On the downside, as pointed out by S.Lott, JMS gives you functionality that you throw away using the (stateless) HTTP protocol: guaranteed ordering & reliability; monitoring; scalability; etc. Are you sure you don’t need these, and won’t need these going forward?
Great question, btw.