BTW, a simple example that includes proposed solutions for all of these requirements would go a long way towards helping me (and maybe others) understand how all the pieces fit together. Maybe something like:
- Define two simple WSGI components: a WSGI middleware and a WSGI application. - Describe how to package each as an indpendent egg. - Describe how to configure an instance of the application. - Describe how to configure an instance of the middleware - Describe how to string them together into a pipeline. - C On Mon, 2005-07-25 at 02:33 -0400, Chris McDonough wrote: > Thanks... > > I'm still confused about high level requirements so please try to be > patient with me as I try get back on track. > > These are the requirements as I understand them: > > 1. We want to be able to distribute WSGI applications and middleware > (presumably in a format supported by setuptools). > > 3. We want to be able to configure a WSGI application in order > to create an application instance. > > 2. We want a way to combine configured instances of those > applications into pipelines and start an "instance" of a pipeline. > > Are these requirements the ones being discussed? If so, which of the > config file formats we've been discussing matches which requirement? > > Thanks, > > - C > > On Sun, 2005-07-24 at 22:24 -0400, Phillip J. Eby wrote: > > At 08:35 PM 7/24/2005 -0400, Chris McDonough wrote: > > >Sorry, I think I may have lost track of where we were going wrt the > > >deployment spec. Specifically, I don't know how we got to using eggs > > >(which I'd really like to, BTW, they're awesome conceptually!) from > > >where we were in the discussion about configuring a WSGI pipeline. What > > >is a "feature"? What is an "import map"? "Entry point"? Should I just > > >get more familiar with eggs to understand what's being discussed here or > > >did I miss a few posts? > > > > I suggest this post as the shortest architectural introduction to the whole > > egg thang: > > > > http://mail.python.org/pipermail/distutils-sig/2005-June/004652.html > > > > It explains pretty much all of the terminology I'm currently using, except > > for the new terms invented today... > > > > Entry points are a new concept, invented today by Ian and myself. Ian > > proposed having a mapping file (which I dubbed an "import map") included in > > an egg's metadata, and then referring to named entries from a pipeline > > descriptor, so that you don't have to know or care about the exact name to > > import. The application or middleware factory name would be looked up in > > the egg's import map in order to find the actual factory object. > > > > I took Ian's proposal and did two things: > > > > 1) Generalized the idea to a concept of "entry points". An entry point is > > a name that corresponds to an import specification, and an optional list of > > "extras" (see terminology link above) that the entry point may > > require. Entry point names exist in a namespace called an "entry point > > group", and I implied that the WSGI deployment spec would define two such > > groups: wsgi.applications and wsgi.middleware, but a vast number of other > > possibilities for entry points and groups exist. In fact, I went ahead and > > implemented them in setuptools today, and realized I could use them to > > register setup commands with setuptools, making it extensible by any > > project that registers entry points in a 'distutils.commands' group. > > > > 2) I then proposed that we extend our deployment descriptor (.wsgi file) > > syntax so that you can do things like: > > > > [foo from SomeProject] > > # configuration here > > > > What this does is tell the WSGI deployment API to look up the "foo" entry > > point in either the wsgi.middleware or wsgi.applications entry point group > > for the named project, according to whether it's the last item in the .wsgi > > file. It then invokes the factory as before, with the configuration values > > as keyword arguments. > > > > This proposal is of course an *extension*; it should still be possible to > > use regular dotted names as section headings, if you haven't yet drunk the > > setuptools kool-aid. But, it makes for interesting possibilities because > > we could now have a tool that reads a WSGI deployment descriptor and runs > > easy_install to find and download the right projects. So, you could > > potentially just write up a descriptor that lists what you want and the > > server could install it, although I think I personally would want to run a > > tool explicitly; maybe I'll eventually add a --wsgi=FILENAME option to > > EasyInstall that would tell it to find out what to install from a WSGI > > deployment descriptor. > > > > That would actually be pretty cool, when you realize it means that all you > > have to do to get an app deployed across a bunch of web servers is to copy > > the deployment descriptor and tell 'em to install stuff. You can always > > create an NFS-mounted cache directory where you put pre-built eggs, and > > EasyInstall would just fetch and extract them in that case. > > > > Whew. Almost makes me wish I was back in my web apps shop, where this kind > > of thing would've been *really* useful to have. > > > > _______________________________________________ > Web-SIG mailing list > [email protected] > Web SIG: http://www.python.org/sigs/web-sig > Unsubscribe: http://mail.python.org/mailman/options/web-sig/chrism%40plope.com > _______________________________________________ Web-SIG mailing list [email protected] Web SIG: http://www.python.org/sigs/web-sig Unsubscribe: http://mail.python.org/mailman/options/web-sig/archive%40mail-archive.com
