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"""
An oversimplified caching HTTP proxy - start it, and configure your browser to
use localhost:8888 as the proxy server. It doesn't do cookies or redirects,
nor does it obey cache-control headers.
The point is to demonstrate :class:`~toro.Event`. Imagine a client requests a
page, and while the proxy is downloading the page from the external site, a
second client requests the same page. Since the page is not yet in cache, an
inefficient proxy would launch a second external request.
This proxy instead places an :class:`~toro.Event` in the cache, and the second
client request waits for the event to be set, thus requiring only a single
external request.
"""
# start-file
from tornado import httpclient, gen, ioloop, web
import toro
class CacheEntry(object):
def __init__(self):
self.event = toro.Event()
self.type = self.body = None
cache = {}
class ProxyHandler(web.RequestHandler):
@web.asynchronous
@gen.coroutine
def get(self):
path = self.request.path
entry = cache.get(path)
if entry:
# Block until the event is set, unless it's set already
yield entry.event.wait()
else:
print path
cache[path] = entry = CacheEntry()
# Actually fetch the page
response = yield httpclient.AsyncHTTPClient().fetch(path)
entry.type = response.headers.get('Content-Type', 'text/html')
entry.body = response.body
entry.event.set()
self.set_header('Content-Type', entry.type)
self.write(entry.body)
self.finish()
if __name__ == '__main__':
print 'Listening on port 8888'
print
print 'Configure your web browser to use localhost:8888 as an HTTP Proxy.'
print 'Try visiting some web pages and hitting "refresh".'
web.Application([('.*', ProxyHandler)], debug=True).listen(8888)
ioloop.IOLoop.instance().start()
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