Wednesday, September 24, 2008

Have it your way

One of the trends I've been seeing a lot of lately in the industry is a movement towards something I would call "build to order". Given that this is something that we see in a number of industries (restaraunt meal preparation, automobile options, custom motorcycles, etc.), it seems no surprise to me that the computing industry wouldn't also be affected by this. We all want to have it our way, not what is provided for the mass of humanity. In a highly competitive industry, having custom solutions can provide differentiation which may be crucial in a value chain. On the other hand, it can also hinder your ability to adapt if it means creating a new custom solution for every customer.

WebSphere Application Server (WAS) has been on a path for some time now to enable custom solutions. Starting way back with WAS 6.0 (2004), astute system administrators may have noticed that we have started packaging the WebSphere runtime in OSGi bundles located in the "plugins" directory. What OSGi does is allow for some separation of concerns and decoupled code selection, as well dynamic hook points for integration. This, in turn, allows WAS to be configured in a variety of ways that were difficult or impossible in the past.

Take, for example, the use of open source. When used in an application, it can help the application developer achieve their goals in a rapid way by utilizing the efforts of the open source community rather than reinventing similar function. The same could also be said for the server. If you are wondering about how much open source gets used in creating WAS, try taking a look at the /lafiles/notices file. Having all this open source in the server can be both good and bad. If an application developer wants to take advantage of it, it's there. However, if it's not the version of the open source the developer wants to use, it can be bad. This is where OSGi's separation of concern can come into play. OSGi modules allow for restricted views of the code in the OSGi bundle. Use of OSGi bundles allows servers to take advantage of open source without actually exposing it to applications. The server's use of open source will not interfere with application's that bundle and use open source. WAS version 7 has refactored much of its runtime to hide open source intended to be used by the runtime. This is coupled with new managed shared libraries, isolated shared library classloaders, and the repackaging of open source into the /optionalLibraries directory to make it much easier to deploy and configure applications. Applications can either bundle the open source they want, or manage multiple shared lib versions of it used by applications in WAS version 7.

Another area where OSGi has helped is in server footprint. OSGi allows for dynamic code use and enables the possibility of load on first use. What this means is that you now have the option of configuring the server to use only as much of the runtime as is necessary. OSGi alone can't do this, so a fair amount of work has gone into getting the WAS version 7 runtime enabled for dynamic provisioning, some of which can be automated, and some of which must be manually configured. One of the most frequent questions I get around this is how much will it reduce the server footprint. As with all performance related questions, it will depend on the scenario. I will say that we've only touched the tip the iceberg for possibilities here and I think we've got a good head start on the competition. For more details, stay tuned to hear from Andrew Spyker as he posts updates on WAS performance.