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This is a python/gevent reimplementation of this EventSource demo https://github.com/remy/eventsource-h5d/
#! /usr/bin/env python2
'''\
This is a reimplementation of a node.js demo of the Server-Sent Events API.
You can find (and compare to) the node.js version at https://github.com/remy/eventsource-h5d/.
'''
from werkzeug import Request, Response, redirect
from werkzeug.wsgi import SharedDataMiddleware
from gevent import pywsgi, spawn, sleep
from gevent.queue import Queue
import os, time
import json
coroutines = []
history = [] # really should be a bound FIFO list
def update_loadavg():
while True:
sleep(1)
with open("/proc/loadavg") as f:
line = f.readline()
loadavg = line.split()[:3]
data = dict(zip(("1","5","15"), loadavg))
broadcast('uptime', data)
def update_time():
while True:
sleep(1)
broadcast('time', time.time());
lastMessageId = 0
def broadcast(event, data):
global lastMessageId
lastMessageId += 1
message = {
'id': lastMessageId,
'event': event,
'data': json.dumps(data)
}
# keep history, but only the last 100 messages
history.append(message)
del history[:-100]
# now notify all active clients
for q in coroutines:
q.put(message)
totalRequests = 0
def handle_stats(req):
if req.headers.get('accept') != 'text/event-stream':
return Response('Not implemented', status=501)
def event_source_iter():
last_event_id = req.headers.get('last-event-id', type=int)
if last_event_id:
# replay history
for message in history:
if message['id'] >= last_event_id:
yield 'event: %(event)s\ndata: %(data)s\nid: %(id)s\n\n' % message
else:
yield 'id\n\n'
q = Queue()
try:
coroutines.append(q)
broadcast('requests', totalRequests)
broadcast('connections', len(coroutines))
for message in q:
yield 'event: %(event)s\ndata: %(data)s\nid: %(id)s\n\n' % message
finally:
coroutines.remove(q)
broadcast('connections', len(coroutines))
headers = [('cache-control', 'no-cache'), ('connection', 'keep-alive')]
return Response(event_source_iter(), headers=headers,
content_type='text/event-stream')
# for wsgi (uwsgi etc)
application = Request.application(handle_stats)
# for standalone
@Request.application
def app(req):
global totalRequests
totalRequests += 1
broadcast('requests', totalRequests)
# fixup file serving etc...
if req.path in ('/index.html', '/'):
return redirect('/eventsource-h5d.html')
if req.path == '/stats':
return handle_stats(req)
return Response('Not Found', status=404)
if __name__ == '__main__':
host, port = '0.0.0.0', 8000
spawn(update_loadavg)
spawn(update_time)
print "Serving on http://%s:%d/" % (host, port)
# poor mans static file serving
app = SharedDataMiddleware(app, {'/': os.path.dirname(__file__)})
server = pywsgi.WSGIServer((host,port), app)
try:
server.serve_forever()
except KeyboardInterrupt:
pass
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Server-Sent Events: server monitor</title>
<style>
body { font-family: monospace; font-size: 18px; margin: 0; }
#connStatus { background: #c00; color: #fff; font-weight: bold; }
#connStatus.open { background: #0c0; }
p { padding: 10px 20px; margin: 0; }
canvas { margin: 10px 20px; border-bottom: 1px solid #ccc; border-top: 1px solid #eee; }
</style>
</head>
<body>
<p id="connStatus">Waiting to connect to server...</p>
<p>Total connected clients: <span id="connections">0</span></p>
<p>Total requests: <span id="requests">0</span></p>
<p>Load: 1 min: <span id="l1">0</span>, 5 min: <span id="l5">0</span>, 15 min: <span id="l15">0</span></p>
<ol id="debug"></ol>
<canvas id="spark"></canvas>
<script>
if (!window.console) {
console = {
log: function (s) {
document.getElementById('debug').innerHTML += '<li><pre>' + s + '</pre></li>';
}
};
}
</script>
<script src="sse.js"></script>
</body>
</html>
(function () {
var connStatus = document.getElementById('connStatus'),
connections = document.getElementById('connections'),
requests = document.getElementById('requests'),
load = { 1: document.getElementById('l1'), 5: document.getElementById('l5'), 15: document.getElementById('l15') },
hasCanvas = !!document.createElement('canvas').getContext;
function connectionOpen(open) {
connStatus.className = open ? 'open' : '';
connStatus.innerHTML = open ? 'Active connection to server' : 'Connection dropped - trying to reopen';
}
function updateConnections(event) {
connections.innerHTML = JSON.parse(event.data);
}
function updateRequests(event) {
requests.innerHTML = JSON.parse(event.data);
}
var lastL1 = null,
history = [];
function updateUptime(event) {
var loadData = JSON.parse(event.data);
for (var key in loadData) {
load[key].innerHTML = loadData[key];
}
if (hasCanvas) {
// normalise
var l1 = (loadData[1] * 100 | 0) + 0.5;
history.unshift(l1);
if (history.length > 400) {
history.splice(400, 400 - history.length);
}
var max = Math.max.apply(Math, history) * 1.25;
ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height);
ctx.save();
ctx.fillStyle = '#000';
ctx.fillText(loadData[1], 0, 50 - (history[0]/max * 50));
ctx.restore();
ctx.beginPath();
for (var i = 0; i < history.length; i++) {
ctx.lineTo(i + 20.5, 50 - (history[i-1]/max * 50) + 0.5);
}
ctx.stroke();
ctx.closePath();
}
}
var source = new EventSource('/stats');
source.addEventListener('open', function () { connectionOpen(true); }, false);
source.addEventListener('error', function () { connectionOpen(false); }, false);
source.addEventListener('connections', updateConnections, false);
source.addEventListener('requests', updateRequests, false);
source.addEventListener('uptime', updateUptime, false);
source.addEventListener('time', function (e) { }, false);
var ctx;
if (hasCanvas) {
ctx = document.getElementById('spark').getContext('2d');
ctx.canvas.height = 50;
ctx.canvas.width = 400;
ctx.fillStyle = '#259BDA';
ctx.strokeStyle = '#259BDA';
}
})();
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