Wednesday, June 24, 2009

NWSGI 2.0: Configuration Changes

One of the two areas to see the most changes in NWSGI 2.0 was its configuration. Some of the options in v1.0 were overloaded in strange ways; even I wasn’t entirely sure what some combinations would produce. There was also the small problem of where to put the configuration section; it varied depending on how NWSGI was installed. For v2.0, both problems needed to be fixed. Doing so required a re-think of how configuration was handled.

Configuring Wildcards

In v1.0, configuring NWSGI to operate in wildcard mode required setting options that were designed for other things in particular ways that made no sense. In v2.0, there is a special <wildcard> element under <wsgi> (replacing the wildcardModule option) that is specifically used for configuring these settings. If the <wildcard> element exists, then NWSGI will ignore the <scriptMappings> element.

The callable option has also been removed from the <wsgi> element as it is no longer necessary (it defaults to “application”). To specify a custom callable name for a script, create a <scriptMapping>.

Where to put it?

The first problem was to put the <wsgi> section in the same place all the time. In v1.0 it could be directly under <configuration> (if you were using xcopy deployment) or under <system.webServer> (if you installed it on IIS7). The two could not necessarily coexist in the same web.config file, either! IIS 7 uses a different configuration assembly (Microsoft.Web.Administration) than ASP.NET (System.Configuration), and they’re no compatible, to boot.

The fix is relatively simple: rather than trying to use the appropriate configuration system from the handler, v2.0 always uses System.Configuration. This means that the <wsgi> section is always directly under <configuration>. The only downside is that the section always has to be declared at the top of web.config:

    <section name="wsgi" type="NWSGI.WsgiSection, NWSGI, Version=, Culture=neutral, PublicKeyToken=41e64ddc1bf1fc86" />

New Options

There are also two new options: compilation and frames. The compilation option controls how IronPython generates code. The frames option is used to control sys._getframe; as tracking frames incurs a performance hit, it must be explicitly enabled.

Wrapping Up

The changes to configuration (which will break any existing configurations) are the main reason for bumping the version to 2.0. The clean up of the options resulted in much cleaner implementations for the management and especially for the handler itself. As always, if you have any comments, let me know.