Eventlet, ZeroMQ, and You

A talk I gave at PyCon Ukraine 2011.

Transcript

1. Eventlet, ZeroMQ & You
   Andrew Godwin
   @andrewgodwin
   

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

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

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

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

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7. 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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8. 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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9. Greening the World
   It's that or monkeypatching.
   http://www.flickr.com/photos/mightyboybrian/3457507731/
   

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

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

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

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14. 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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15. 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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16. Experiences from production
    There's still race conditions and bad libraries.
    http://www.flickr.com/photos/iamdabe/4931554963/
    

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

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

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

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20. Version Three: Fresh, Separate
    Codenamed ”Mantrid”
    

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21. 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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22. 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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23. 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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24. ZeroMQ
    I was too lazy to use an Ø.
    http://www.flickr.com/photos/andresrueda/2926348197/
    

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

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26. REQ / REP
    PUB / SUB
    PUSH / PULL
    

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27. 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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28. 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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29. 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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30. 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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31. The restrictions
    It's not quite too good to be true.
    http://www.flickr.com/photos/maistora/3237164755/
    

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

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

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

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37. Logging clients
    They're the things that make logs
    

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

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

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

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