k4ml · August 29, 2015 14:09
diff --git a/sse.py b/sse.py
 """
 Tail file to browser using Server Sent Events (SSE) + gevent.

 Based on http://the.taoofmac.com/space/blog/2014/11/16/1940#python-patterns--take-two

 Twisted+websocket implementation - https://github.com/k4ml/websocket_stdout_example

 Requirements:-

    sudo pip install bottle
    sudo apt-get install python-gevent

 References
 ==========
 http://www.html5rocks.com/en/tutorials/eventsource/basics/
 http://stackoverflow.com/questions/260273/most-efficient-way-to-search-the-last-x-lines-of-a-file-in-python
 https://www.reddit.com/r/learnpython/comments/1uufki/tail_f_equivalent_in_python/
 """

 import time
 import json

 from bottle import run
 from gevent import monkey; monkey.patch_all()
 from bottle import request, response, get, route


 def sse_pack(d):
    """Pack data in SSE format"""
    buffer = ''
    for k in ['retry','id','event','data']:
        if k in d.keys():
            buffer += '%s: %s\n' % (k, d[k])
    return buffer + '\n'

 def tail(fn, sleep=0.1):
    f = open(fn)
    f.seek (0, 2)           # Seek @ EOF
    fsize = f.tell()        # Get Size
    f.seek (max (fsize-1024, 0), 0) # Set pos @ last n chars
    while True:
        l = f.readline()
        if l:
            yield l
        else:
            time.sleep(sleep)


 @get("/")
 def index():
    return """<!DOCTYPE html>
    <html>
    <head>
      <meta charset="utf-8" />
    </head>
    <body>
      <script>
        var source = new EventSource('/stream');
        source.addEventListener('delta', function(e) {
            var data = JSON.parse(e.data);
            document.body.innerHTML += data.key + '<br>';
        }, false);
      </script>
    </body>
    </html>
    """

 @get("/stream")
 def stream_generator():
    # Keep event IDs consistent
    event_id = 0
    if 'Last-Event-Id' in request.headers:
        event_id = int(request.headers['Last-Event-Id']) + 1

    # Set up our message payload with a retry value in case of connection failure
    # (that's also the polling interval to be used as fallback by our polyfill)
    msg = {
        'retry': '2000'
    }

    # Provide an initial data dump to each new client
    response.headers['content-type'] = 'text/event-stream'
    response.headers['Access-Control-Allow-Origin'] = '*'
    msg.update({
         'event': 'init',
         'data' : json.dumps({'key': 'hello'}),
         'id'   : event_id
    })
    yield sse_pack(msg)

    # Now give them deltas as they arrive (say, from a message broker)
    event_id += 1    
    msg['event'] = 'delta'
    for data in tail('/var/log/syslog'):
        # block until you get new data (from a queue, pub/sub, zmq, etc.)
        msg.update({
             'event': 'delta',
             'data' : json.dumps({'key': data}),
             'id'   : event_id
        })
        print sse_pack(msg)
        yield sse_pack(msg)
        event_id += 1

 run(server="gevent")
	"""
	Tail file to browser using Server Sent Events (SSE) + gevent.

	Based on http://the.taoofmac.com/space/blog/2014/11/16/1940#python-patterns--take-two

	Twisted+websocket implementation - https://github.com/k4ml/websocket_stdout_example

	Requirements:-

	sudo pip install bottle
	sudo apt-get install python-gevent

	References
	==========
	http://www.html5rocks.com/en/tutorials/eventsource/basics/
	http://stackoverflow.com/questions/260273/most-efficient-way-to-search-the-last-x-lines-of-a-file-in-python
	https://www.reddit.com/r/learnpython/comments/1uufki/tail_f_equivalent_in_python/
	"""

	import time
	import json

	from bottle import run
	from gevent import monkey; monkey.patch_all()
	from bottle import request, response, get, route


	def sse_pack(d):
	"""Pack data in SSE format"""
	buffer = ''
	for k in ['retry','id','event','data']:
	if k in d.keys():
	buffer += '%s: %s\n' % (k, d[k])
	return buffer + '\n'

	def tail(fn, sleep=0.1):
	f = open(fn)
	f.seek (0, 2) # Seek @ EOF
	fsize = f.tell() # Get Size
	f.seek (max (fsize-1024, 0), 0) # Set pos @ last n chars
	while True:
	l = f.readline()
	if l:
	yield l
	else:
	time.sleep(sleep)


	@get("/")
	def index():
	return """<!DOCTYPE html>
	<html>
	<head>
	<meta charset="utf-8" />
	</head>
	<body>
	<script>
	var source = new EventSource('/stream');
	source.addEventListener('delta', function(e) {
	var data = JSON.parse(e.data);
	document.body.innerHTML += data.key + '<br>';
	}, false);
	</script>
	</body>
	</html>
	"""

	@get("/stream")
	def stream_generator():
	# Keep event IDs consistent
	event_id = 0
	if 'Last-Event-Id' in request.headers:
	event_id = int(request.headers['Last-Event-Id']) + 1

	# Set up our message payload with a retry value in case of connection failure
	# (that's also the polling interval to be used as fallback by our polyfill)
	msg = {
	'retry': '2000'
	}

	# Provide an initial data dump to each new client
	response.headers['content-type'] = 'text/event-stream'
	response.headers['Access-Control-Allow-Origin'] = '*'
	msg.update({
	'event': 'init',
	'data' : json.dumps({'key': 'hello'}),
	'id' : event_id
	})
	yield sse_pack(msg)

	# Now give them deltas as they arrive (say, from a message broker)
	event_id += 1
	msg['event'] = 'delta'
	for data in tail('/var/log/syslog'):
	# block until you get new data (from a queue, pub/sub, zmq, etc.)
	msg.update({
	'event': 'delta',
	'data' : json.dumps({'key': data}),
	'id' : event_id
	})
	print sse_pack(msg)
	yield sse_pack(msg)
	event_id += 1

	run(server="gevent")