Django template tag for simulating ESI rendering on dev and rendering ESI tags in production. Use ESI_ON=True to render locally.

esi.py

from django import template
from django.test.client import Client
from django.conf import settings
from django.core.cache import cache
from django.utils.hashcompat import md5_constructor

register = template.Library()

@register.simple_tag
def esi(url, timeout=10):
    if getattr(settings, 'ESI_ON', True):
        
        cachekey = md5_constructor("esi_%s" % url).hexdigest()
        cached_esi = cache.get(cachekey)
        if cached_esi:
            return cached_esi
        else:
            import socket
            from urllib2 import urlopen
            socket_default_timeout = socket.getdefaulttimeout()
            if timeout is not None:
                try:
                    socket_timeout = float(timeout)
                except ValueError:
                    raise template.TemplateSyntaxError, "timeout argument of geturl tag, if provided, must be convertible to a float"
                try:
                    socket.setdefaulttimeout(socket_timeout)
                except ValueError:
                    raise template.TemplateSyntaxError, "timeout argument of geturl tag, if provided, cannot be less than zero"
            try:
                try:
                    content = urlopen(url).read()
                finally: # reset socket timeout
                    if timeout is not None:
                        socket.setdefaulttimeout(socket_default_timeout)
            except:
                content = ''
                
            cache.set(cachekey, content, 360)
            return content
    else:
        return u'<esi:include src="%s"/>' % url