SOAP: slow or fast?

There's an interesting discussion going on here between Michi and Jim about the performance of SOAP. I wasn't going to get involved in what could easily become a "PC verus Mac, Unix versus Windows" debate, but I'll add my 2 cents worth.

I agree with them both, to a point.

I'm sure ICE is fast (I too haven't used it). I do know that CORBA implementations these days are very fast too and message service implementations (for example) like AMS are built for speed. When I started out doing my PhD back in the mid 1980's, my first task was to help write and improve Rajdoot, one of the first RPC mechanisms around. Even then, when a fast network was 10 mbps (if you were lucky) and we used Whitechapels or Sun 360's, we could regularly get round trips on 5ms for messages up to 1K in size (packet fragmentation/re-assembly happens above this, so this was the maximum critical packet size). Not fast by today's standards, but fast back then. Having been working with SOAP and Web Services for 5 years now, I know it's slow compared to what we had in 1986, so it simply doesn't compare to what's possible these days. So, I agree with Michi's point that on that (yes, we have tried compression over the years too, and got the same results as Michi - it works, but you've got to use it carefully.)

However, and this is where I also agree with Jim, SOAP performance can be improved. The sorts of things that go on under the covers today in terms of XML parsing, for example, are pretty inefficient. Next time you want to see, just pop up something like OptimizeIt and watch what happens. I'm pretty confident that developers can and will improve on this. As an analogy, back when IONA released the first version of Orbix it was the market leader but its performance was terrible compared to later revisions. (Opcodes were shipped as strings, for a start!) I'm not singling out IONA - this is a pattern that many other ORB providers followed. So, I agree with Jim: SOAP doesn't have to be this slow - it can be improved.

But this is where I stop agreeing and come back to the fact that it's beginning to sound like the "PC verus Mac, Unix versus Windows" debates of old. You're not comparing like with like.

This is definitely a case of using the right tool for the right job, combined with some unfortunate commercial realities. If you want interoperablity with other vendors (eventually pretty much any other vendor on the planet), then you'd go the SOAP route: there is no logical argument to the contrary. CORBA didn't get mass adoption, DCE failed before it, and despite Microsoft's power, so did DCOM. Eric has some interesting things to say on the subject here, but the reason SOAP works well is because of XML, HTTP (IMO) and pretty much universal adoption. I can't see that changing. In the forseeable future, I can't see the likes of Microsoft, IBM, Oracle, BEA etc. agreeing on a single protocol and infrastructure as they have with SOAP. To be honest, I think they were forced into the current situation because of the mass take-up of the original Web: they like vendor lock-in and had managed to maintain it for decades prior to Tim's arrival on the scene.

But you pay a heavy price for this kind of interoperability. There are inherent performance problems in SOAP that I just can't see going away. We may be able to chip at the surface and perhaps even make bit dents, but fundamentally I'm confident that SOAP performance versus something like ICE (or CORBA) will always be a one-sided contest. However, a contest of interoperability will be just as one-sided, with SOAP winning. From the moment I got into Web Services, I've said that I can't see it (and SOAP) replacing distributed environments like CORBA everywhere. It frustrates me at times when I see clients trying to do just that though and then complaining that the results aren't fast enough! If I want to go off-road, I'll buy a Land Rover; but if I want speed, give me a Ferrari any day! Distributed systems such as CORBA have been heavily optimised over the years and use binary encodings as much as possible - with the resultant impact on interoperability and performance. But that is fine. That's what they're intended for. Certainly if I was interested in high performance, I wouldn't be looking at SOAP or Web Services, but at CORBA (or something similar).

So in summary: of course there will be performance improvements for the SOAP infrastructure. There may even be a slow evolution to a pure binary, extremely efficient distributed invocation mechanism that looks similar to those systems that have gone before. But it's not strictly necessary and I don't see it happening as a priority. Use SOAP for interoperability. It lowers the integration barrier. But if you are really interested in performance and/or can impose a single solution on your corporate infrastructure, you may be better off looking elsewhere, to something like CORBA, or maybe even ICE.