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RethinkDB Tornado & Event Machine

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Ryan Paul RethinkDB Evangelist @segphault

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Introduction What is RethinkDB?

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What is RethinkDB? • Open source database for building realtime web applications • NoSQL database that stores schemaless JSON documents • Distributed database that is easy to scale

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Built for Realtime Apps • Subscribe to change notifications from database queries • No more polling — the database pushes changes to your app • Reduce the amount of plumbing needed to stream live updates

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Subscribe to change notifications on database queries Changefeeds

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r.table("users").changes() Changefeeds Track changes on the users table

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Changefeeds • The changes command returns a cursor that receives updates • Each update includes the new and old value of the modified record

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Changefeeds r.table("users") .filter({name: "Bob"}).delete() Changefeed output: { new_val: null, old_val: { id: '362ae837-2e29-4695-adef-4fa415138f90', name: 'Bob', ... } }

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Changefeeds r.table("players") .orderBy({index: r.desc("score")}) .limit(3).changes() Track top three players by score Chain the changes command to an actual ReQL query:

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Async Frameworks Tornado & EventMachine

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Async Web Frameworks Tornado EventMachine

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Async Web Frameworks • Event-driven programming • Non-blocking network I/O • Well-suited for the realtime Web

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Async Web Frameworks • New in RethinkDB 2.0 Python & Ruby drivers • Download the release candidate today • Official release coming in April

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Async Web Frameworks • Perform queries asynchronously • Consume multiple changefeeds at the same time without blocking

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Tornado import rethinkdb as r from tornado import ioloop, gen r.set_loop_type("tornado") @gen.coroutine def print_changes(): conn = yield r.connect(host="localhost", port=28015) feed = yield r.table("table").changes().run(conn) while (yield feed.fetch_next()) change = yield feed.next() print(change) ioloop.IOLoop.current().add_callback(print_changes)

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Tornado import rethinkdb as r from tornado import ioloop, gen r.set_loop_type("tornado") @gen.coroutine def print_changes(): conn = yield r.connect(host="localhost", port=28015) feed = yield r.table("table").changes().run(conn) while (yield feed.fetch_next()) change = yield feed.next() print(change) ioloop.IOLoop.current().add_callback(print_changes) Configure the event loop

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Tornado import rethinkdb as r from tornado import ioloop, gen r.set_loop_type("tornado") @gen.coroutine def print_changes(): conn = yield r.connect(host="localhost", port=28015) feed = yield r.table("table").changes().run(conn) while (yield feed.fetch_next()) change = yield feed.next() print(change) ioloop.IOLoop.current().add_callback(print_changes) Add the coroutine decorator

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Tornado import rethinkdb as r from tornado import ioloop, gen r.set_loop_type("tornado") @gen.coroutine def print_changes(): conn = yield r.connect(host="localhost", port=28015) feed = yield r.table("table").changes().run(conn) while (yield feed.fetch_next()) change = yield feed.next() print(change) ioloop.IOLoop.current().add_callback(print_changes) Connect to the database

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Tornado import rethinkdb as r from tornado import ioloop, gen r.set_loop_type("tornado") @gen.coroutine def print_changes(): conn = yield r.connect(host="localhost", port=28015) feed = yield r.table("table").changes().run(conn) while (yield feed.fetch_next()) change = yield feed.next() print(change) ioloop.IOLoop.current().add_callback(print_changes) Perform the ReQL query

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Tornado import rethinkdb as r from tornado import ioloop, gen r.set_loop_type("tornado") @gen.coroutine def print_changes(): conn = yield r.connect(host="localhost", port=28015) feed = yield r.table("table").changes().run(conn) while (yield feed.fetch_next()) change = yield feed.next() print(change) ioloop.IOLoop.current().add_callback(print_changes) Iterate over changefeed changes

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Tornado import rethinkdb as r from tornado import ioloop, gen r.set_loop_type("tornado") @gen.coroutine def print_changes(): conn = yield r.connect(host="localhost", port=28015) feed = yield r.table("table").changes().run(conn) while (yield feed.fetch_next()) change = yield feed.next() print(change) ioloop.IOLoop.current().add_callback(print_changes) Fetch the latest change

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Tornado import rethinkdb as r from tornado import ioloop, gen r.set_loop_type("tornado") @gen.coroutine def print_changes(): conn = yield r.connect(host="localhost", port=28015) feed = yield r.table("table").changes().run(conn) while (yield feed.fetch_next()) change = yield feed.next() print(change) ioloop.IOLoop.current().add_callback(print_changes) Print the change to stdout

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Tornado import rethinkdb as r from tornado import ioloop, gen r.set_loop_type("tornado") @gen.coroutine def print_changes(): conn = yield r.connect(host="localhost", port=28015) feed = yield r.table("table").changes().run(conn) while (yield feed.fetch_next()) change = yield feed.next() print(change) ioloop.IOLoop.current().add_callback(print_changes) Run coroutine in the background

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EventMachine require "rethinkdb" include RethinkDB::Shortcuts conn = r.connect host: "localhost", port: 28015 EM.run do r.table("table").changes.em_run(conn) do |err, change| puts change end end

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EventMachine require "rethinkdb" include RethinkDB::Shortcuts conn = r.connect host: "localhost", port: 28015 EM.run do r.table("table").changes.em_run(conn) do |err, change| puts change end end Connect to the database

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EventMachine require "rethinkdb" include RethinkDB::Shortcuts conn = r.connect host: "localhost", port: 28015 EM.run do r.table("table").changes.em_run(conn) do |err, change| puts change end end Create an EventMachine block

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EventMachine require "rethinkdb" include RethinkDB::Shortcuts conn = r.connect host: "localhost", port: 28015 EM.run do r.table("table").changes.em_run(conn) do |err, change| puts change end end Perform the ReQL query

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EventMachine require "rethinkdb" include RethinkDB::Shortcuts conn = r.connect host: "localhost", port: 28015 EM.run do r.table("table").changes.em_run(conn) do |err, change| puts change end end Print the change to stdout

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Building Web Apps Realtime Ruby app with Faye

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Faye Framework • Open source pub/sub framework for realtime messaging • Communication between frontend and backend • Supports Ruby and Node.js on the backend

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Faye Framework EM.run do ... App = Faye::RackAdapter.new Sinatra::Application, mount: "/faye" conn = r.connect host: "localhost", port: 28015 r.table("todo").changes.em_run(conn) do |err, change| App.get_client.publish("/todo/update", change) end ... end Server-side Ruby code

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Faye Framework EM.run do ... App = Faye::RackAdapter.new Sinatra::Application, mount: "/faye" conn = r.connect host: "localhost", port: 28015 r.table("todo").changes.em_run(conn) do |err, change| App.get_client.publish("/todo/update", change) end ... end Initialize Faye and bind URL route

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Faye Framework EM.run do ... App = Faye::RackAdapter.new Sinatra::Application, mount: "/faye" conn = r.connect host: "localhost", port: 28015 r.table("todo").changes.em_run(conn) do |err, change| App.get_client.publish("/todo/update", change) end ... end Connect to the database

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Faye Framework EM.run do ... App = Faye::RackAdapter.new Sinatra::Application, mount: "/faye" conn = r.connect host: "localhost", port: 28015 r.table("todo").changes.em_run(conn) do |err, change| App.get_client.publish("/todo/update", change) end ... end Perform the ReQL query

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Faye Framework EM.run do ... App = Faye::RackAdapter.new Sinatra::Application, mount: "/faye" conn = r.connect host: "localhost", port: 28015 r.table("todo").changes.em_run(conn) do |err, change| App.get_client.publish("/todo/update", change) end ... end Publish the update to a channel

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Faye Framework faye.subscribe("/todo/update", function(data) { console.log(data); }); Client-side JavaScript code

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DEMO