CherryPy3 and IIS 6.0

Question

I have a small Python web application using the Cherrypy framework. I am by no means an expert in web servers.

I got Cherrypy working with Apache using mod_python on our Ubuntu server. This time, however, I have to use Windows 2003 and IIS 6.0 to host my site.

The site runs perfectly as a stand alone server - I am just so lost when it comes to getting IIS running. I have spent the past day Googling and blindly trying any and everything to get this running.

I have all the various tools installed that websites have told me to (Python 2.6, CherrpyPy 3, ISAPI-WSGI, PyWin32) and have read all the documentation I can. This blog was the most helpful:

http://whatschrisdoing.com/blog/2008/07/10/turbogears-isapi-wsgi-iis/

But I am still lost as to what I need to run my site. I can't find any thorough examples or how-to's to even start with. I hope someone here can help!

Cheers.

Answer 1

I run CherryPy behind my IIS sites. There are several tricks to get it to work.

1. When running as the IIS Worker Process identity, you won't have the same permissions as you do when you run the site from your user process. Things will break. In particular, anything that wants to write to the file system will probably not work without some tweaking.
2. If you're using setuptools, you probably want to install your components with the -Z option (unzips all eggs).
3. Use win32traceutil to track down problems. Be sure that in your hook script that you're importing win32traceutil. Then, when you're attempting to access the web site, if anything goes wrong, make sure it gets printed to standard out, it'll get logged to the trace utility. Use 'python -m win32traceutil' to see the output from the trace.

It's important to understand the basic process to get an ISAPI application running. I suggest first getting a hello-world WSGI application running under ISAPI_WSGI. Here's an early version of a hook script I used to validate that I was getting CherryPy to work with my web server.

#!python

"""
Things to remember:
easy_install munges permissions on zip eggs.
anything that's installed in a user folder (i.e. setup develop) will probably not work.
There may still exist an issue with static files.
"""


import sys
import os
import isapi_wsgi

# change this to '/myapp' to have the site installed to only a virtual
#  directory of the site.
site_root = '/'

if hasattr(sys, "isapidllhandle"):
    import win32traceutil

appdir = os.path.dirname(__file__)
egg_cache = os.path.join(appdir, 'egg-tmp')
if not os.path.exists(egg_cache):
    os.makedirs(egg_cache)
os.environ['PYTHON_EGG_CACHE'] = egg_cache
os.chdir(appdir)

import cherrypy
import traceback

class Root(object):
    @cherrypy.expose
    def index(self):
        return 'Hai Werld'

def setup_application():
    print "starting cherrypy application server"
    #app_root = os.path.dirname(__file__)
    #sys.path.append(app_root)
    app = cherrypy.tree.mount(Root(), site_root)
    print "successfully set up the application"
    return app

def __ExtensionFactory__():
    "The entry point for when the ISAPIDLL is triggered"
    try:
        # import the wsgi app creator
        app = setup_application()
        return isapi_wsgi.ISAPISimpleHandler(app)
    except:
        import traceback
        traceback.print_exc()
        f = open(os.path.join(appdir, 'critical error.txt'), 'w')
        traceback.print_exc(file=f)
        f.close()

def install_virtual_dir():
    import isapi.install
    params = isapi.install.ISAPIParameters()
    # Setup the virtual directories - this is a list of directories our
    # extension uses - in this case only 1.
    # Each extension has a "script map" - this is the mapping of ISAPI
    # extensions.
    sm = [
        isapi.install.ScriptMapParams(Extension="*", Flags=0)
    ]
    vd = isapi.install.VirtualDirParameters(
        Server="CherryPy Web Server",
        Name=site_root,
        Description = "CherryPy Application",
        ScriptMaps = sm,
        ScriptMapUpdate = "end",
        )
    params.VirtualDirs = [vd]
    isapi.install.HandleCommandLine(params)

if __name__=='__main__':
    # If run from the command-line, install ourselves.
    install_virtual_dir()

This script does several things. It (a) acts as the installer, installing itself into IIS [install_virtual_dir], (b) contains the entry point when IIS loads the DLL [__ExtensionFactory__], and (c) it creates the CherryPy WSGI instance consumed by the ISAPI handler [setup_application].

If you place this in your \inetpub\cherrypy directory and run it, it will attempt to install itself to the root of your IIS web site named "CherryPy Web Server".

You're also welcome to take a look at my production web site code, which has refactored all of this into different modules.

Answer 2

OK, I got it working. Thanks to Jason and all his help. I needed to call

cherrypy.config.update({
  'tools.sessions.on': True
})
return cherrypy.tree.mount(Root(), '/', config=path_to_config)

I had this in the config file under [/] but for some reason it did not like that. Now I can get my web app up and running - then I think I will try and work out why it needs that config update and doesn't like the config file I have...