Practical EventMachine

EventMachine (EM) is an event-driven concurrency library for Ruby, akin to Python's Twisted or Node.js. In this talk we'll explore some of the patterns and abstractions behind EM, how we can apply those ideas to our applications and how the library has been used by companies like GitHub and Heroku.

Transcript

1. Practical
   EventMachine
   

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2. @febuiles
   

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3. http://goo.gl/Oqe4SI
   

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4. Events
   events
   

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5. $("#door").on("open", function(){
   log("We got a new Joe in town...");
   });
   

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6. WHY EVENTS?
   

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7. i/o
   

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8. latency
   

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9. MOST APPLICATIONS
   ARE I/O BOUND
   I/O BOUND
   

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10. https://github.com/blog/517-unicorn
    YOUR TYPICAL
    CONCURRENCY
    MODEL
    

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11. server = TCPServer.new(1337)
    !
    while client = server.accept
    message = client.readline
    client.write "> #{message}"
    client.close
    end
    

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12. server = TCPServer.new(1337)
    !
    while true
    Thread.new(server.accept) do |client|
    message = client.readline
    client.write "> #{message}"
    client.close
    end
    end
    

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13. THE REACTOR
    

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14. What is a reactor?
    

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15. while true
    events.each do |event|
    event.process
    end
    end
    

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16. Chernobyl, 1986
    

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17. New Safe Confinement (NSC)
    

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18. DON’T BLOCK THE REACTOR
    

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19. Reactor.run {
    on(:receive) do |msg|
    return if invalid_message(msg)?
    !
    device = Device.find(msg.device_id)
    device.update(position: msg.position)
    end
    }
    

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20. Reactor.run {
    on(:receive) do |msg|
    return if invalid_message(msg)?
    !
    device = Device.find(msg.device_id)
    device.update(position: msg.position)
    end
    }
    

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21. What is EventMachine?
    

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22. EventMachine is an
    event-driven I/O and
    lightweight concurrency
    library for Ruby.
    

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23. ?
    

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24. EventMachine is a fast,
    simple event-
    processing library for
    Ruby programs
    

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25. A PIMPED REACTOR.
    

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26. Why EventMachine?
    

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27. EventMachine is dead.
    

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29. EventMachine is dead
    EventMachine is stable.
    

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30. Heroku
    Thin
    Campfire
    GitHub
    Rainbows
    EngineYard
    

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31. module Echo
    def receive_data(message)
    send_data "> #{message}"
    end
    end
    !
    EM.run {
    EM.start_server "0.0.0.0", 1337, Echo
    }
    

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32. module Echo
    def post_init
    puts "Client connected"
    end
    !
    def receive_data(message)
    send_data "> #{message}"
    end
    !
    def unbind
    puts "Client disconnected"
    end
    end
    !
    EM.run {
    EM.start_server "0.0.0.0", 1337, Echo
    }
    

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33. EM HANDLERS
    VS
    CALLBACK HELL
    

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34. server = AsyncTCPServer.new("0.0.0.0", 1337)
    !
    server.on(:accept) {
    message = client.async_read
    !
    message.on(:ready) {
    client.write "> #{message}"
    client.close
    }
    }
    !
    server.on(:connect) {
    puts "Client connected"
    }
    !
    server.on(:disconnect) {
    puts "Client disconnected"
    }
    

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35. events

    post_init
    connection_completed
    receive_data

    unbind
    ssl_handshake_completed
    methods
    start_tls
    get_peername

    send_data

    close_connection
    close_connection_after_writing
    proxy_incoming_to
    pause/resume
    

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36. Mixing Paradigms
    

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37. module Echo
    def receive_data(data)
    message = parse_data(data)
    return if invalid_message(message)?
    !
    device = Device.find(message.device_id)
    device.update(position: message.position)
    send_data :updated
    end
    end
    !
    EM.run {
    EM.start_server "0.0.0.0", 1337, Echo
    }
    

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38. module Echo
    def receive_data(data)
    message = parse_data(data)
    return if invalid_message(message)?
    !
    device = Device.find(message.device_id)
    device.update(position: message.position)
    send_data :updated
    end
    end
    !
    EM.run {
    EM.start_server "0.0.0.0", 1337, Echo
    }
    

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39. DON’T BLOCK THE REACTOR
    

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41. DATA STORES
    !
    cassandra
    couchdb
    memcached
    mongodb
    mysql
    postgresql
    redis
    

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42. HTTP
    !
    HttpRequest
    Faraday
    

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43. PROTOCOLS
    !
    tcp
    udp
    amqp
    smtp
    stomp
    xmpp
    dns
    websockets
    and more…
    

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44. Other
    !
    EM.popen
    EM.defer
    

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45. module Graham
    def receive_data(number)
    calculate = proc {
    graham(number)
    }
    !
    report = proc { |result|
    send_data(result)
    }
    !
    EM.defer(calculate, report)
    end
    end
    

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46. EM API
    

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47. EM API
    !
    EM::timer
    EM::deferrable
    EM::queue
    EM::channel
    EM.watch_file
    EM.watch_process
    

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48. Closing Thoughts
    

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49. Events are hard.
    

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50. Evented Programming
    for Evented Problems
    

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51. DON’T
    BLOCK
    THE
    REACTOR
    !!1
    

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52. Thanks :)
    !
    http://mheroin.com/rubyconfar
    @febuiles
    

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53. Credits
    Federico’s illustration: Pablo Pérez
    Nuclear cooling tower: Jonathan Brennan
    Some code samples: Aman Gupta & Jeremy Cheung
    Unicorn diagram: GitHub
    The rest: Wikipedia
    

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