Created
January 14, 2015 22:54
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PostgreSQL notifications with Psycopg2 and Eventlet (from http://initd.org/psycopg/articles/2010/12/01/postgresql-notifications-psycopg2-eventlet/)
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| import psycopg2 | |
| from psycopg2.extensions import ISOLATION_LEVEL_AUTOCOMMIT | |
| import eventlet | |
| from eventlet import wsgi | |
| from eventlet import websocket | |
| from eventlet.hubs import trampoline | |
| dsn = "dbname=test" # customise this | |
| def dblisten(q): | |
| """ | |
| Open a db connection and add notifications to *q*. | |
| """ | |
| cnn = psycopg2.connect(dsn) | |
| cnn.set_isolation_level(ISOLATION_LEVEL_AUTOCOMMIT) | |
| cur = cnn.cursor() | |
| cur.execute("LISTEN data;") | |
| while 1: | |
| trampoline(cnn, read=True) | |
| cnn.poll() | |
| while cnn.notifies: | |
| n = cnn.notifies.pop() | |
| q.put(n) | |
| @websocket.WebSocketWSGI | |
| def handle(ws): | |
| """ | |
| Receive a connection and send it database notifications. | |
| """ | |
| q = eventlet.Queue() | |
| eventlet.spawn(dblisten, q) | |
| while 1: | |
| n = q.get() | |
| print(n) | |
| ws.send(n.payload) | |
| def dispatch(environ, start_response): | |
| if environ['PATH_INFO'] == '/data': | |
| return handle(environ, start_response) | |
| else: | |
| start_response('200 OK', | |
| [('content-type', 'text/html')]) | |
| return [page] | |
| page = b""" | |
| <html> | |
| <head><title>pushdemo</title> | |
| <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.1/jquery.min.js"></script> | |
| <style type="text/css"> | |
| .bar {width: 20px; height: 20px;} | |
| </style> | |
| <script> | |
| window.onload = function() { | |
| ws = new WebSocket("ws://localhost:7000/data"); | |
| ws.onmessage = function(msg) { | |
| bar = $('#' + msg.data); | |
| bar.width(bar.width() + 10); | |
| } | |
| } | |
| </script> | |
| </head> | |
| <body> | |
| <div style="width: 400px;"> | |
| <div id="red" class="bar" | |
| style="background-color: red;"> </div> | |
| <div id="green" class="bar" | |
| style="background-color: green;"> </div> | |
| <div id="blue" class="bar" | |
| style="background-color: blue;"> </div> | |
| </div> | |
| </body> | |
| </html> | |
| """ | |
| if __name__ == "__main__": | |
| listener = eventlet.listen(('127.0.0.1', 7000)) | |
| wsgi.server(listener, dispatch) | |
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