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# coffeeshop
# A lightweight REST-orientated pubsub mechanism
# (c) 2009 DJ Adams
# See https://github.com/qmacro/coffeeshop/
import os
import re
import cgi
import logging
import wsgiref.handlers
import datetime
#import urllib2
from models import Channel, Subscriber, Message, Delivery
from bucket import agoify
from google.appengine.ext.webapp import template
from google.appengine.ext import webapp
from google.appengine.ext import db
from google.appengine.api.labs import taskqueue
from google.appengine.api import urlfetch
from django.utils import simplejson
VERSION = "0.01"
DEBUG = True
# Name of task queue for message distribution
QUEUE_DISTRIBUTION='msgdist'
# Statuses
STATUS_DELIVERED='DELIVERED'
CT_JSON = 'application/json'
if DEBUG:
logging.getLogger().setLevel(logging.DEBUG)
def isNumber(n):
try:
int(n); return True
except ValueError:
pass
class EntityRequestHandler(webapp.RequestHandler):
"""Base RequestHandler supplying common methods
for retrieving entities such as channels and subscribers
"""
def _getentity(self, type, id):
entity = None
# id must be numeric
if not isNumber(id):
self.response.out.write("%s must be numeric (got %s)" % (type.__name__, id))
self.response.set_status(404)
return
id = int(id)
if id == 0:
self.response.out.write("%s cannot be zero (got %s)" % (type.__name__, id))
self.response.set_status(404)
return
entity = type.get_by_id(int(id))
if entity is None:
self.response.out.write("%s %s not found" % (type.__name__, id))
self.response.set_status(404)
return
return entity
class MainPageHandler(webapp.RequestHandler):
def get(self):
template_values = {
'version': VERSION,
'server_software': os.environ.get("SERVER_SOFTWARE", "unknown"),
}
path = os.path.join(os.path.dirname(__file__), 'index.html')
self.response.out.write(template.render(path, template_values))
class ChannelContainerHandler(webapp.RequestHandler):
"""Handler for main /channel/ resource
"""
def get(self):
"""Show list of channels
"""
# TODO: paging
channels = []
for channel in db.GqlQuery("SELECT * FROM Channel ORDER BY created DESC"):
channels.append({
'channelid': channel.key().id(),
'name': channel.name,
'created': channel.created,
'created_ago': agoify(channel.created),
})
template_values = {
'channels': channels,
}
path = os.path.join(os.path.dirname(__file__), 'channel_list.html')
self.response.out.write(template.render(path, template_values))
def post(self):
"""Handles a POST to the /channel/ resource
Creates a new channel resource (/channel/{id}) and returns
its Location with a 201
"""
channel = Channel()
name = self.request.get('name').rstrip('\n')
channel.name = name
channel.put()
# Not sure I like this ... re-put()ing
if len(channel.name) == 0:
channel.name = 'channel-' + str(channel.key().id())
channel.put()
# If we've got here from a web form, redirect the user to the
# channel list, otherwise return the 201
if self.request.get('channelsubmissionform'):
self.redirect('/channel/')
else:
self.response.headers['Location'] = self.request.url + str(channel.key().id()) + '/'
self.response.set_status(201)
class ChannelSubmissionformHandler(webapp.RequestHandler):
"""Handles the channel submission form resource
/channel/submissionform/
"""
def get(self):
"""Renders channel submission form, that has a POST action to
the /channel/ resource
"""
path = os.path.join(os.path.dirname(__file__), 'channelsubmissionform.html')
self.response.out.write(template.render(path, {}))
class ChannelHandler(EntityRequestHandler):
"""Handles an individual channel resource
e.g. /channel/123/
Shows when it was created, and a link to subscribers (if there are any)
"""
def get(self, channelid):
"""Return general information on the channel"""
channel = self._getentity(Channel, channelid)
if channel is None: return
anysubscribers = Subscriber.all().filter('channel =', channel).fetch(1)
template_values = {
'channel': channel,
'anysubscribers': anysubscribers,
}
path = os.path.join(os.path.dirname(__file__), 'channel_detail.html')
self.response.out.write(template.render(path, template_values))
# The publish bit!
def post(self, channelid):
"""Handles a message publish to this channel"""
channel = self._getentity(Channel, channelid)
if channel is None: return
contenttype = self.request.headers['Content-Type']
# Save message
message = Message(
contenttype = contenttype,
body = self.request.body,
channel = channel,
)
message.put()
# for subscriber in Subscriber.all().filter('channel =', channel):
subscribers = Subscriber.all().filter('channel =', channel)
if subscribers.count():
for subscriber in subscribers:
# Set up delivery of message to subscriber
delivery = Delivery(
message = message,
recipient = subscriber,
)
delivery.put()
# Kick off a task to distribute message
taskqueue.Task(
url='/distributor/' + str(message.key())
).add(QUEUE_DISTRIBUTION)
logging.debug("Delivery queued for %d subscribers of channel %s" % (subscribers.count(), channelid))
else:
logging.debug("No subscribers for channel %s" % (channelid, ))
# TODO should we return a 202 instead of a 302?
# Actually I think it's just a 201, as we've created a new (message) resource
# self.redirect(self.request.url + 'message/' + str(message.key()))
# Try to detect whether we're from the coffeeshop browser, and if so, return a 302
self.response.headers['Location'] = self.request.url + "message/%s" % str(message.key())
if contenttype == "application/x-www-form-urlencoded" and self.request.get('messagesubmissionform') == "coffeeshop":
self.response.set_status(302)
else:
self.response.set_status(201)
def delete(self, channelid):
"""Handle deletion of a channel. Only allow if there are no subscribers"""
channel = self._getentity(Channel, channelid)
if channel is None: return
# Check the subscribers
nrsubscribers = Subscriber.all().filter('channel =', channel).count()
if nrsubscribers:
# Can't delete if subscribers still exist
self.response.set_status(405, "CANNOT DELETE - %s SUBSCRIBERS" % nrsubscribers)
self.response.headers['Allow'] = "GET, POST"
else:
channel.delete()
self.response.set_status(204)
class ChannelSubscriberSubmissionformHandler(webapp.RequestHandler):
"""Handles the subscriber submission form for a given channel,
i.e. resource /channel/{id}/subscriber/submissionform
"""
def get(self, channelid):
"""Handles a GET to the /channel/{id}/subscriber/submissionform resource
"""
channel = Channel.get_by_id(int(channelid))
if channel is None:
self.response.out.write("Channel %s not found" % (channelid, ))
self.response.set_status(404)
return
template_values = {
'channel': channel,
'channelsubscriberresource': '/channel/' + channelid + '/subscriber/',
}
path = os.path.join(os.path.dirname(__file__), 'subscribersubmissionform.html')
self.response.out.write(template.render(path, template_values))
class ChannelSubscriberContainerHandler(webapp.RequestHandler):
"""Handles the subscribers for a given channel, i.e. resource
/channel/{id}/subscriber/
"""
def get(self, channelid):
"""Handles a GET to the /channel/{id}/subscriber/ resource
"""
channel = Channel.get_by_id(int(channelid))
if channel is None:
self.response.out.write("Channel %s not found" % (channelid, ))
self.response.set_status(404)
return
subscribers = []
for subscriber in Subscriber.all().filter('channel =', channel):
subscribers.append({
'subscriberid': subscriber.key().id(),
'name': subscriber.name,
'resource': subscriber.resource,
'created': subscriber.created,
})
template_values = {
'channel': channel,
'subscribers': subscribers,
}
path = os.path.join(os.path.dirname(__file__), 'channelsubscriber.html')
self.response.out.write(template.render(path, template_values))
def post(self, channelid):
"""Handles a POST to the /channel/{id}/subscriber/ resource
which is to add a subscriber to the channel
"""
# Get channel first
channel = Channel.get_by_id(int(channelid))
if channel is None:
self.response.out.write("Channel %s not found" % (channelid, ))
self.response.set_status(404)
return
# Add subscriber
name = self.request.get('name').rstrip('\n')
resource = self.request.get('resource').rstrip('\n')
subscriber = Subscriber()
subscriber.channel = channel
subscriber.name = name
subscriber.resource = resource
subscriber.put()
# Not sure I like this ... re-put()ing
if len(subscriber.name) == 0:
subscriber.name = 'subscriber-' + str(subscriber.key().id())
subscriber.put()
# If we've got here from a web form, redirect the user to the
# channel subscriber resource, otherwise return the 201
if self.request.get('subscribersubmissionform'):
self.redirect(self.request.path_info)
else:
self.response.headers['Location'] = self.request.url + str(subscriber.key().id()) + '/'
self.response.set_status(201)
class ChannelSubscriberHandler(EntityRequestHandler):
"""Handles a given channel subscriber, i.e. resource
/channel/{id}/subscriber/{id}/
"""
def get(self, channelid, subscriberid):
channel = self._getentity(Channel, channelid)
if channel is None: return
subscriber = self._getentity(Subscriber, subscriberid)
if subscriber is None: return
template_values = {
'channel': channel,
'subscriber': subscriber,
}
path = os.path.join(os.path.dirname(__file__), 'subscriber_detail.html')
self.response.out.write(template.render(path, template_values))
def delete(self, channelid, subscriberid):
"""Handle deletion of a subscribers.
Only allow if there are no outstanding deliveries."""
channel = self._getentity(Channel, channelid)
if channel is None: return
subscriber = self._getentity(Subscriber, subscriberid)
if subscriber is None: return
nrdeliveries = Delivery.all().filter('recipient =', subscriber).filter('status !=', STATUS_DELIVERED).count()
if nrdeliveries:
# Can't delete if deliveries still outstanding
self.response.set_status(405, "CANNOT DELETE - %s DELIVERIES OUTSTANDING" % nrdeliveries)
self.response.headers['Allow'] = "GET"
else:
subscriber.delete()
self.response.set_status(204)
class SubscriberContainerHandler(webapp.RequestHandler):
"""Handles the subscriber container resource, i.e.
/subscriber/
GET will just return a list of subscribers, by channel
"""
def get(self):
subscribers = db.GqlQuery("SELECT * FROM Subscriber "
"ORDER BY channel ASC, created DESC")
template_values = {
'subscribers': subscribers,
}
path = os.path.join(os.path.dirname(__file__), 'subscriber.html')
self.response.out.write(template.render(path, template_values))
class ChannelMessageHandler(webapp.RequestHandler):
"""Handles message delivery status resources in the form of
/channel/{cid}/message/{mid}
"""
def get(self, channelid, messageid):
message = Message.get(messageid)
if message is None:
self.response.out.write("Message %s not found" % (messageid, ))
self.response.set_status(404)
return
deliveries = Delivery.all().filter('message =', message)
channelurl = "%s://%s/channel/%d/" % (self.request.scheme, self.request.host, message.channel.key().id())
# Poor conneg
if (self.request.headers.has_key('Accept')
and self.request.headers['Accept'] == CT_JSON):
logging.info("JSON requested")
deliveryinfo = []
for d in deliveries:
deliveryinfo.append({
'recipient': "%ssubscriber/%d/" % (channelurl, d.recipient.key().id()),
'status': d.status,
'timestamp': d.updated.strftime("%Y-%m-%dT%H:%M:%SZ"),
})
info = {
'message': {
'resource': "%smessage/%s" % (channelurl, str(message.key())),
'key': str(message.key()),
'created': message.created.strftime("%Y-%m-%dT%H:%M:%SZ"),
'channel': channelurl,
'delivery': deliveryinfo,
},
}
self.response.out.write(simplejson.dumps(info))
self.response.headers['Content-Type'] = CT_JSON
return
template_values = {
'message': message,
#'deliveries': Delivery.all().filter('message =', message),
'deliveries': deliveries,
}
path = os.path.join(os.path.dirname(__file__), 'messagedetail.html')
self.response.out.write(template.render(path, template_values))
class ChannelMessageContainerHandler(EntityRequestHandler):
"""Handles the message container resource for a channel, in the form of
/channel/{cid}/message/
"""
def get(self, channelid):
channel = self._getentity(Channel, channelid)
if channel is None: return
template_values = {
'channel': channel,
'messages': Message.all().filter('channel =', channel),
}
path = os.path.join(os.path.dirname(__file__), 'messagelist.html')
self.response.out.write(template.render(path, template_values))
class ChannelMessageSubmissionformHandler(EntityRequestHandler):
"""Handles the channel message submission form for a given channel,
i.e. resource /channel/{id}/message/submissionform
"""
def get(self, channelid):
channel = self._getentity(Channel, channelid)
if channel is None: return
template_values = {
'channel': channel,
}
path = os.path.join(os.path.dirname(__file__), 'messagesubmissionform.html')
self.response.out.write(template.render(path, template_values))
class MessageHandler(webapp.RequestHandler):
"""Handles the message overview resource, i.e.
/message/
GET will just return a list of messages, by channel
Not sure whether this resource will cause confusion where you'd think
you can POST to this resource (which you can't, of course).
"""
def get(self):
# This seems expensive. TODO: refactor
messages = []
for message in db.GqlQuery("SELECT * FROM Message ORDER BY created DESC"):
recipients = Delivery.all().filter('message =', message).count()
delivered = Delivery.all().filter('message =', message).filter('status =', STATUS_DELIVERED).count()
messages.append({
'message': message,
'recipients': recipients,
'delivered': delivered,
})
template_values = {
'messages': messages,
}
path = os.path.join(os.path.dirname(__file__), 'message.html')
self.response.out.write(template.render(path, template_values))
class DistributorWorker(webapp.RequestHandler):
"""Task Queue worker - distributes a given message. The task queue
mechanism may retry this if not all the deliveries have been made.
It should keep retrying until they all have been made.
"""
def post(self, messageid):
# Retrieve the message, make sure it exists
message = Message.get(messageid)
if message is None:
logging.debug("Message %s does not exist, returning 200" % (messageid, ))
self.response.set_status(200)
return
# Assume all deliveries are successful (i.e. this task is done)
deliveriessucceeded = True
# For this message, process those deliveries that have not yet been
# delivered (status will be None)
for delivery in Delivery.all().filter('message =', message).filter('status =', None):
logging.debug("Processing delivery %s" % (delivery.key(), ))
# Make the delivery with a POST to the recipient's resource
# sending the published body, with the published body's content-type
status = 999
try:
result = urlfetch.fetch(
url = delivery.recipient.resource,
payload = message.body,
method = urlfetch.POST,
headers = { 'Content-Type': message.contenttype },
follow_redirects = False,
)
status = result.status_code
except:
logging.error("urlfetch encountered an EXCEPTION")
# If we've had a successful status then consider this
# particular delivery done. Otherwise, mark the delivery
# as failed.
if status < 400:
delivery.status = STATUS_DELIVERED
delivery.put()
else:
deliveriessucceeded = False
# If there are failed deliveries, mark this task as failed
# so that the task queue mechanism will retry.
if not deliveriessucceeded:
self.response.set_status(500)
def main():
application = webapp.WSGIApplication([
(r'/', MainPageHandler),
(r'/channel/submissionform/?', ChannelSubmissionformHandler),
(r'/channel/(.+?)/subscriber/submissionform', ChannelSubscriberSubmissionformHandler),
(r'/channel/(.+?)/subscriber/', ChannelSubscriberContainerHandler),
(r'/channel/(.+?)/subscriber/(.+?)/', ChannelSubscriberHandler),
(r'/channel/(.+?)/message/submissionform/?', ChannelMessageSubmissionformHandler),
(r'/channel/(.+?)/message/(.+)', ChannelMessageHandler),
(r'/channel/(.+?)/message/', ChannelMessageContainerHandler),
(r'/channel/(.+?)/', ChannelHandler),
(r'/channel/?', ChannelContainerHandler),
(r'/subscriber/', SubscriberContainerHandler),
(r'/message/', MessageHandler),
(r'/distributor/(.+?)', DistributorWorker),
], debug=True)
wsgiref.handlers.CGIHandler().run(application)
if __name__ == "__main__":
main()