README: Event Source Library for Python
This library implements W3C Draft's on event-source:
It enables a halfduplex communication from server to client, but initiated by the client, through standard HTTP(S) communication.
- Fairly recent python (tested with 2.7)
- Fairly recent tornado (tested with 2.2.1)
Launch the server:
eventsource-server -P 8888 -i -k 50000
Launch the client:
eventsource-client 42:42:42:42:42:42 -r 5000 -P 8888
eventsource-request 42:42:42:42:42:42 ping "42" eventsource-request 42:42:42:42:42:42 close
Command Line arguments
eventsource/listener.py or eventsource-server:
usage: eventsource/listener.py [-h] [-H HOST] [-P PORT] [-d] [-j] [-k KEEPALIVE] [-i] Event Source Listener optional arguments: -h, --help show this help message and exit -H HOST, --host HOST Host to bind on -P PORT, --port PORT Port to bind on -d, --debug enables debug output -j, --json to enable JSON Event -k KEEPALIVE, --keepalive KEEPALIVE Keepalive timeout, in milliseconds -i, --id to generate identifiers
eventsource/client.py or eventsource-client:
usage: eventsource/client.py [-h] [-H HOST] [-P PORT] [-d] [-r RETRY] token Event Source Client positional arguments: token Token to be used for connection optional arguments: -h, --help show this help message and exit -H HOST, --host HOST Host to connect to -P PORT, --port PORT Port to be used connection -d, --debug enables debug output -r RETRY, --retry RETRY Reconnection timeout
eventsource/send_request.py or eventsource-request:
usage: eventsource/send_request.py [-h] [-H HOST] [-P PORT] [-j] token action [data] Generates event for Event Source Library positional arguments: token Token to be used for connection action Action to send data Data to be sent optional arguments: -h, --help show this help message and exit -H HOST, --host HOST Host to connect to -P PORT, --port PORT Port to be used connection -j, --json Treat data as JSON
You can install it by getting it from pypi:
pip install event-source-library
or by getting this repository and install it manually:
python setup.py install
To develop, you can use buildout:
pip install zc.buildout # if you haven't got it buildout ls bin/
Or you can do:
python setup.py develop
which will deploy the commands globally like an install, but still linked to the current sources.
On the server side, basically all you have to do is to add the following to your code:
from eventsource import listener application = tornado.web.Application([ (r"/(.*)/(.*)", listener.EventSourceHandler, dict(event_class=EVENT, keepalive=KEEPALIVE)), ]) application.listen(PORT) tornado.ioloop.IOLoop.instance().start()
PORTis an integer for the port to bind to
KEEPALIVEis an integer for the timeout between two keepalive messages (to protect from disconnections), in milliseconds
EVENTis a eventsource.listener.Event based class, either one you made or
eventsource.listener.StringEvent: Each event gets and resends multiline strings
eventsource.listener.StringIdEvent: Each event gets and resends multiline strings, with an unique id for each event
eventsource.listener.JSONEvent: Each event gets and resends JSON valid strings
eventsource.listener.JSONIdEvent: Each event gets and resends JSON valid string, with an unique id for each event
See http://www.tornadoweb.org/en/stable/web.html#application-configuration for more details.
To extend the behaviour of the event source library, without breaking eventsource definition, the Event based classes implements all processing elements that shall be done on events.
There is two abstract classes that defines Event:
eventsource.listener.Event : defines the constructor of an Event
eventsource.listener.EventId : defines an always incrementing id handler
here is an example to create a new Event that takes multiline data and join it in a one line string seperated with semi-colons.
class OneLineEvent(Event): ACTIONS = ["ping",Event.FINISH] """Property to enable multiline output of the value""" def get_value(self): # replace carriage returns by semi-colons # this method shall always return a list (even if one value) return [";".join([line for line in self._value.split('\n')])] value = property(get_value,set_value)
And now, I want to add basic id support to OneLineEvent, in OneLineEventId, nothing is easier
class OneLineEventId(OneLineEvent,EventId): id = property(EventId.get_value)
Or if I want the id to be a timestamp:
import time class OneLineTimeStampEvent(OneLineEvent): id = property(lambda s: "%f" % (time.time(),))
You can change the behaviour of a few things in a Event-based class:
GETaction to open a connection (per default "poll")
POSTaction to close a connection (per default "close")
POSTaction to define the timeout after reconnecting on network disconnection (per default "0", which means disabled)
- in the
Event.ACTIONSlist, you define what POST actions are allowed, per default, only Event.FINISH is allowed.
Event.content_typecontains the "content_type" that will be asked for every form (it is not enforced).
To change the way events are generated, you can directly call
to create a new event to be sent. But the post action is best, at least while WSGI can't handle
correctly long polling connections.
Python Event Source Library (c) 2012 Bernard Pratz Patches by Ian Whyman, Коренберг Марк and Max Suraev This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 3 of the License. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/. EOF