Dev-Picayune

So after hearing about CherryPy’s WSGI server while at PyCon (I went to the Pylons/TG2 classes), I decided, like others have, to see if I could host a Django site with it here where I work. There are several references out there about using that server code with Django, but I had a tough time getting to the point where I could actually use it to handle the Admin media. Some of the articles were slightly out of date with changes made to the most recent version of the CherryPy WSGI server, so while this is drawing off of several other folk’s work (like Eric Florenzano and DjangoCerise ), I present what I did to make it work while also realizing that this is probably still very incomplete. I am just hoping this will help someone get started.

Prior to the code, I downloaded just the wsgiserver.py from CherryPy. You can get the latest from trunk if you’re running Linux, with just a command like this:

wget http://svn.cherrypy.org/trunk/cherrypy/wsgiserver/__init__.py -O wsgiserver.py

Then I also wanted to have some logging capabilities, so I discovered Paste’s TransLogger middleware. All you have to do is download the translogger.py file from the paste project (sorry no quicky command for that, I grabbed it via the browser and I am too lazy to get you the command for that).

So with those 2 files (wsgiserver.py and translogger.py) now in the main directory of my particular django project (dash2 is the name in my example), I created a new cherryserve.py in that same directory as well.

import wsgiserver
#This can be from cherrypy import wsgiserver if you're not running it standalone.
import sys
import os
import django.core.handlers.wsgi
from django.core.servers.basehttp import AdminMediaHandler
from translogger import TransLogger
 
if __name__ == "__main__":
    sys.path.append('/home/swilcox/projects')
    os.environ['DJANGO_SETTINGS_MODULE'] = 'dash2.settings'
 
    app = AdminMediaHandler(django.core.handlers.wsgi.WSGIHandler())
    logged_app = TransLogger(app)
    server = wsgiserver.CherryPyWSGIServer(	
        ('127.0.0.1', 8080),
        logged_app,
        server_name='luz.lifeway.org',
        numthreads = 20,
    )
 
    try:
        server.start()
    except KeyboardInterrupt:
        server.stop()

So why did I do the path trickery up there? Well, because in my development environment, I don’t want my entire projects directory normally on my python path. Feel free to call me paranoid. But to get the server to work correctly with the django code, I needed it there. For a production server, the sys.path.append business wouldn’t normally need to be there, because I would have my apps or projects directory as part of the Python path.

Also note that if you needed to serve multiple apps, with this newer version of the wsgiserver.py, you would want to set them all up in a WSGIPathInfoDispatcher object first and then pass that in to the CherryPyWSGIServer instead of logged_app.

I think the other fields are pretty self-explanatory… ports, IP address, threads, etc…

The Admin Media trick is using app = AdminMediaHandler(django.core.handlers.wsgi.WSGIHandler()) instead of just the WSGIHandler by itself.

If you don’t want the logger, you just pass in app instead of logged_app.

So just as a bookmark to myself, I wanted to document what all I was working on from a technical perspective.

On the work front, I’ve recently deployed a Django app that folks are just totally loving. It’s actually a hacked together group of scripts to import data and export data to two different legacy systems. In the middle, I use the Django admin stuff to allow folks to maintain the data, and scripts at the beginning and end of the day handle import and export duties.

I finally started hacking around on WordPress themes. I’ve not gotten very far but hopefully in the next week or so, I’ll have new designs for both sites.

Then, with regard to PyCon, I submitted some talk proposals. Not sure I should have bothered, but it seemed like the thing to do. Now I’m just curious to see if any of my proposals are accepted. One of the proposals is for a project I’ve only begun really gathering the pieces for. I’ve resolved that whether the talk is approved or not, I’m going to work away at the project and then I’ll either have a talk or I’ll have a lightning talk to present. I’ll be blogging my way through my progress here, so should have some interesting stuff to post.

I’ve finally gotten tired of my poor little blog getting attacked by spammers. Actually, it was just one in particular and I know I could’ve done some IP blocking or added to the protection scheme on my comments, but rather than working more on Pumpkinvine, I’ve now switched to WordPress. And while it seems like I’m giving up, it’s really so I have the chance to catch my breath while I use all the WordPress plugins to handle the spam for me. But for reference, I ought to package up my most recent version of Pumpkinvine and make it available for folks although it’s really a pretty rough collection of PHP scripts that approximate the same style as blosxom. So why bother creating another system? But it seemed like a good idea at the time. Probably the neatest part of Pumpkinvine was going to be the switchable back-ends so you could choose between text files, SQLite, MySQL or something else by just changing a single setting. Of course, the only back-end I had done was the text files-based core.

Ultimately, I was tired of messing with PHP. I’d like to go with more Python. Django appears to the fastest way to get to having a working blog, but lack of personal free time, and lack of desire to fight with FastCGI and Dreamhost to get up and running, kind of dampened my spirits. So I’ll settle for my clever Python script that I wrote to convert from Pumpkinvine to WordPress and some time that I’ll need to devote to learning how to create WordPress themes.

I found myself needing to do a fairly complicated thing. Well, it’s not complicated, but for a DOS batch file, it seemed complicated. The problem I was facing: to insert some “official” DOS command stuff into a .bat file that is run on all computers in our entire organization. I have no idea how many machines were talking about here but I would guess the number to be in the 5,000+ range or higher. Specifically, this is our official domain login script. Yikes. I don’t like having anything to do with something that gets touched this often. One screwup in there and it’s not a good thing. The problem is that we have a special group of machines (about 130) that are not registered on the domain. Now we need them on the domain but we don’t want to run some of the programs that our “Software Taliban” uses for monitoring machines. All of these special machines have a common naming scheme which is the letter S followed by a 7-digit number. So my task was insert some DOS .bat stuff in the existing .bat file that will run without external dependencies (other than whatever is already guaranteed to be there). All I knew for sure was that the environment variable COMPUTERNAME would be filled with the name of the computer and that my special machines were running 2K or XP and that either way, the OS environment variable would be filled with “Windows_NT”.

I also wanted to make sure I didn’t catch machines that were named “Snoopy” or anything like that. So for lack of a better way, I chose the following as my DOS string substitution method:

SET CN=%COMPUTERNAME% 
SET CN=%CN:0=x% 
SET CN=%CN:1=x% 
SET CN=%CN:2=x% 
SET CN=%CN:3=x% 
SET CN=%CN:4=x% 
SET CN=%CN:5=x% 
SET CN=%CN:6=x% 
SET CN=%CN:7=x% 
SET CN=%CN:8=x% 
SET CN=%CN:9=x% 
IF /i "%CN%"=="Sxxxxxx" GOTO END

The magic here is the funky %variable:y=x% stuff. Essentially, it’s string replacement where any ‘y’ is replaced with an ‘x’. This then normalizes the name into something I can compare against. Doing it this way also guarantees that I am comparing the length as well. So while it isn’t pretty, I was pleasantly surprised to find it was possible to do in DOS. There is also a method for getting a substring using a similar syntax: %variable:~s,l% where s is the starting position (1-based) and l is the length of the sub-string. Talk about obscure. But then again, how often do you have to stick to plain old DOS .bat files?

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