shad's blog

CirruxCache 0.2.2 has just been released. It contains some bugfixes (thanks to Devattas to have reported errors on Datastore latency). Webpy has been updated to the last version.

I have also updated the documentation, especially I brought more details on Point of Presence configuration and usage of cron tasks for garbage collection.

Finally, some of the users reported me that there is a real problem with the cached object size limit (currently 1MB). I am working on the solution, I will take advantage of the new Blobstore service on AppEngine to store objects. Maybe I will keep the Datastore only for meta-data. This solution will raise the cache object limit to 50MB.

Stay tuned :)

Webpy is a tiny web framework. I use it a lot for my web-services applications. In general, I let my web server (lighttpd) to handle virtual hosting. But as you may know, I am working on a CDN solution on top of Google App Engine, named CirruxCache. In that case, while I have absolutely no control on the server configuration, I need to handle virtual hosting from the code. Webpy maps urls by iterating through a tuple. So my solution is quite simple: wrapping the tuple to override the __iter__ function according to an environment variable (HTTP_HOST). Let's take this basic webpy example, without vhosting:

import web

urls = ('/(.*)', 'hello')

class hello(object):
def GET(self, name):
if not name:
name = 'World'
return 'Hello, %s' % name

if __name__ == "__main__":
app = web.application(urls, globals())
app.run()
Let's add the VhostMapper class:

import web

urls = {
'default' : ('/(.*)', 'hello'),
'my-vhost.domain.tld' : ('/(.*)', 'helloVhost')
}

class hello(object):
def GET(self, name):
if not name:
name = 'World'
return 'Hello, %s !' % name

class helloVhost(object):
def GET(self, name):
return 'Hello %s' % web.ctx.environ['HTTP_HOST']

class VhostMapper(object):
def __iter__(self):
url = urls['default']
if 'HTTP_HOST' in web.ctx.environ:
vhost = web.ctx.environ['HTTP_HOST']
if vhost in urls:
url = urls[vhost]
return iter(url)

if __name__ == "__main__":
app = web.application(VhostMapper(), globals())
app.run()
Finally, you can use curl or wget to test your vhosts:

$> curl -H "Host: my-vhost.domain.tld" http://localhost:8080/

It is not so early to announce that the next version of CirruxCache will handle virtual hosting :) I am sure this simple hack can be easily reproduced to use virtual hosting in some other Rest frameworks.