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Eventlet, ZeroMQ & You Andrew Godwin @andrewgodwin

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Who am I? http://www.flickr.com/photos/maistora/3014414972

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The Plan http://www.flickr.com/photos/snapsi42/2609025344/

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Eventlet Asynchronous concurrency framework http://www.flickr.com/photos/pagedooley/2814895287/

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import eventlet from eventlet.green import urllib2 urls = ['http://ep.io', 'http://t.co'] results = [] def fetch(url): results.append(urllib2.urlopen(url).read()) for url in urls: eventlet.spawn(fetch, url)

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Cooperative Threading You have to yield control. http://www.flickr.com/photos/nickwheeleroz/3406931272/

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import eventlet import time def thread1(): time.sleep(5) # Does not yield print 'five seconds a' eventlet.spawn(thread1) time.sleep(5) # Does not yield print 'five seconds b'

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import eventlet import time def thread1(): eventlet.sleep(5) print 'five seconds a' eventlet.spawn(thread1) eventlet.sleep(5) print 'five seconds b'

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Greening the World It's that or monkeypatching. http://www.flickr.com/photos/mightyboybrian/3457507731/

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import urllib2 from eventlet.green import urllib2 import zmq from eventlet.green import zmq import socket from eventlet.green import socket

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Nice Primitives Not to mention less race conditions. http://www.flickr.com/photos/mightyboybrian/3457507731/

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from eventlet.timeout import Timeout try: with Timeout(30): do_stuff() except Timeout: abort_abort()

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from eventlet.semaphore import Semaphore sem = Semaphore(1) with sem: use_resource()

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from eventlet.queue import Queue q = Queue() def worker(): while True: print q.get() def producer(): while True: eventlet.sleep(1) q.put('lol') eventlet.spawn(worker) eventlet.spawn(producer)

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from eventlet import GreenPool from eventlet.pools import Pool conns = Pool(create=make_db_connection) threads = GreenPool(10) def querier(id): with pool.item() as conn: conn.execute('... WHERE id = %s', [id]) pool.imap(querier, [1, 2, 3, 4, 5])

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Experiences from production There's still race conditions and bad libraries. http://www.flickr.com/photos/iamdabe/4931554963/

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Case Study: Epio Loadbalancer Now at version three. http://www.flickr.com/photos/jasohill/118616905/

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Version One: HAProxy + reloader Occasionally slow, occasionally didn't reload.

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Version Two: Custom Integrated Worked alright, but leaked sockets.

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Version Three: Fresh, Separate Codenamed ”Mantrid”

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address = ('0.0.0.0', 80) family = socket.AF_INET sock = eventlet.listen(address, family) eventlet.serve( sock, self.handle, concurrency = 10000, )

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address = ('127.0.0.1', 8042) family = socket.AF_INET sock = eventlet.listen(address, family) management_app = ManagementApp(self) wsgi.server( sock, management_app.handle, )

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class Spin(Action): def handle(self, sock, read_data, path, headers): while True: # Sleep first eventlet.sleep(self.check_interval) # Check for another action action = self.balancer.resolve_host(self.host) if not isinstance(action, Spin): return action.handle( sock, read_data, path, headers )

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ZeroMQ I was too lazy to use an Ø. http://www.flickr.com/photos/andresrueda/2926348197/

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Not a message queue More like 'better sockets'. http://www.flickr.com/photos/96dpi/3816391053/

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REQ / REP PUB / SUB PUSH / PULL

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from eventlet.green import zmq ctx = zmq.Context() sock = ctx.socket(zmq.REQ) sock.connect('tcp://127.0.0.1:1234') sock.connect('tcp://127.0.0.1:4321') sock.send('hi there') print sock.recv()

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from eventlet.green import zmq ctx = zmq.Context() sock = ctx.socket(zmq.REP) sock.bind('tcp://0.0.0.0:1234') while True: message = sock.recv() sock.send('you said: %s' % message)

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from eventlet.green import zmq ctx = zmq.Context() sock = ctx.socket(zmq.PUB) sock.connect('tcp://127.0.0.1:1234') sock.send('Hello, world!')

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from eventlet.green import zmq ctx = zmq.Context() sock = ctx.socket(zmq.SUB) sock.bind('tcp://0.0.0.0:1234') while True: print sock.recv()

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The restrictions It's not quite too good to be true. http://www.flickr.com/photos/maistora/3237164755/

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Advanced ZeroMQ & Eventlet When one greenthread is not enough http://www.flickr.com/photos/maistora/3237164755/

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sock = ctx.socket(zmq.REQ) sock.send('help me! you're my only hope!') try: with Timeout(30): response = sock.recv() deal_with(response) except Timeout: cleanup()

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@zmq_loop(zmq.XREP, 8000) def handle_request(string): eventlet.sleep(10) return string * 2

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try: parts = sock.recv_multipart(flags=zmq.NOBLOCK) except zmq.ZMQError, e: if e.errno == zmq.EAGAIN: eventlet.sleep(0.1) continue else: raise identities = parts[:parts.index("")] def call(identities, data): result = func(self, data) sock.send_multipart(identities + ["", result]) eventlet.spawn_n(call, identities, parts[-1])

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Case Study: Epio Logging We really, really like data http://www.flickr.com/photos/jasohill/118616905/

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Logging clients They're the things that make logs

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Logging servers They're the things that save and store logs

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# Servers zmq.PULL -> Recieves logs zmq.REP -> Lets website query for log data # Clients zmq.PUSH -> Sends logs, connected to all servers

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Conclusions Where Andrew waffles for a bit. http://www.flickr.com/photos/oimax/108058706/

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Thanks. Andrew Godwin @andrewgodwin http://aeracode.org