Practical EventMachine - Speaker Deck

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Practical EventMachine

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@febuiles

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http://goo.gl/Oqe4SI

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Events events

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

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WHY EVENTS?

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i/o

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latency

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MOST APPLICATIONS ARE I/O BOUND I/O BOUND

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

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

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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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THE REACTOR

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What is a reactor?

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

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Chernobyl, 1986

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New Safe Confinement (NSC)

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DON’T BLOCK THE REACTOR

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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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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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What is EventMachine?

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

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

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A PIMPED REACTOR.

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Why EventMachine?

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EventMachine is dead.

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No content

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EventMachine is dead EventMachine is stable.

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Heroku Thin Campfire GitHub Rainbows EngineYard

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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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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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EM HANDLERS VS CALLBACK HELL

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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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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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Mixing Paradigms

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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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DON’T BLOCK THE REACTOR

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No content

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DATA STORES ! cassandra couchdb memcached mongodb mysql postgresql redis

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HTTP ! HttpRequest Faraday

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

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Other ! EM.popen EM.defer

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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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EM API

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

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Closing Thoughts

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Events are hard.

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Evented Programming for Evented Problems

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DON’T BLOCK THE REACTOR !!1

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

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