Real-Time applications in Phoenix

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REAL-TIME APPLICATIONS IN PHOENIX @ChrisKeathley / keathley@carbonﬁve.com / keathley.io

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Chris Keathley @ChrisKeathley / keathley@carbonﬁve.com / keathley.io

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Lets talk about Realtime

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Rails + Faye

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Rails Faye

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Node + socket.io

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socket.io socket.io Redis

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Complexity

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Balance

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2 million connections per server

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2 million connections per server 400 million users

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2 million connections per server 400 million users 30 Engineers

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Erlang

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Heroku RabbitMQ Riak Facebook

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Elixir

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Types iex> 1 # integer iex> 0x1F # integer iex> 1.0 # float iex> true # boolean iex> :atom # atom / symbol iex> "elixir" # string iex> [1, 2, 3] # list iex> {1, 2, 3} # tuple iex> %{:a => 1, 2 => :b} # map

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Pattern Matching iex(1)> x = 3 3

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Pattern Matching iex(1)> x = 3 3 iex(2)> y = x 3

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Pattern Matching iex(1)> x = 3 3 iex(2)> y = x 3 iex(3)> 3 = x 3

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Pattern Matching is an assertion

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Pattern Matching iex(3)> 3 = x 3

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Pattern Matching iex(4)> %{a: a, b: b} = %{a: "hello", b: "world"} %{a: "hello", b: "world"} iex(5)> a "hello" iex(6)> b "world" iex(7)>

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Immutability

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Processes iex(9)> pid = spawn fn -> 1 + 2 end #PID<0.68.0> iex(10)> self() #PID<0.57.0>

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Processes iex> parent = self() #PID<0.41.0> iex> spawn fn -> send(parent, {:hello, self()}) end #PID<0.48.0> iex> receive do ...> {:hello, pid} -> "Got hello from #{inspect pid}" ...> end "Got hello from #PID<0.48.0>"

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Processes C# Thread: 4Mb

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Processes C# Thread: 4Mb Java Thread: 256k

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Processes C# Thread: 4Mb Java Thread: 256k Erlang Process: 1k

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OTP GenServer Supervisors GenFSM GenEvent Observer Dialyzer

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Let It Crash

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❤ Real-time

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http://www.phoenixframework.org/blog/the-road-to-2-million- websocket-connections

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Demo http://bit.ly/1OEWVQ2

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Lets build an app Controllers & Channels Models Supervisor Trees Changesets

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Lets build an app Controllers & Channels Models Supervisor Trees Changesets

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Controllers defmodule Conflicted.PageController do use Conflicted.Web, :controller def index(conn, _params) do render conn, "index.html" end end

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Controllers Conflicted <%= render Conflicted.PageView, "index.html" %> <%= if Mix.env == :dev do %> <% else %> "> <% end %>

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import { Socket } from 'phoenix-socket' let socket = new Socket("/socket") socket.connect()

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Sockets defmodule Conflicted.UserSocket do use Phoenix.Socket ## Channels channel "tweets:*", Conflicted.TweetChannel ## Transports transport :websocket, Phoenix.Transports.WebSocket transport :longpoll, Phoenix.Transports.LongPoll def connect(_params, socket) do {:ok, socket} end def id(_socket), do: nil end

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## Channels channel "tweets:*", Conflicted.TweetChannel

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defmodule Conflicted.TweetChannel do use Phoenix.Channel def join("tweets:stream", _message, socket) do tweets = Conflicted.Repo.all(Conflicted.Tweet) {:ok, tweets, socket} end def join("tweets:" <> _private_room_id, _params, _socket) do {:error, %{reason: "unauthorized"}} end # … end

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def join("tweets:stream", _message, socket) do

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def join("tweets:stream", _message, socket) do When a client “joins” the channel

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def join("tweets:stream", _message, socket) do When a client “joins” the channel Pattern matching on the channel name

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def join("tweets:stream", _message, socket) do When a client “joins” the channel Pattern matching on the channel name The client socket connection

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def join("tweets:stream", _message, socket) do

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def join("tweets:stream", _message, socket) do tweets = Repo.all(Tweet) {:ok, tweets, socket} end

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def join("tweets:stream", _message, socket) do tweets = Repo.all(Tweet) {:ok, tweets, socket} end Retrieves all “tweets” from the database

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def join("tweets:stream", _message, socket) do tweets = Repo.all(Tweet) {:ok, tweets, socket} end Retrieves all “tweets” from the database Return a tuple including the socket

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def join("tweets:stream", _message, socket) do tweets = Repo.all(Tweet) {:ok, tweets, socket} end

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defmodule Conflicted.TweetChannel do use Phoenix.Channel def join("tweets:stream", _message, socket) do tweets = Repo.all(Tweet) {:ok, tweets, socket} end def join("tweets:" <> _private_room_id, _params, _socket) do {:error, %{reason: "unauthorized"}} end # … end Return an error if the client tries to join any other channel

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Lets build an app Controllers & Channels Models Supervisor Trees Changesets

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DB Repo Query Data

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query = from t in Tweet, select: [t.text, t.likes], where: [t.author == “@chriskeathley”], order_by: [desc: t.inserted_at], limit: 30 tweets = Conflicted.Repo.all(query)

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Lets build an app Controllers & Channels Models Supervisor Trees Changesets

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import { Socket } from 'phoenix-socket' let socket = new Socket("/socket") socket.connect() let channel = socket.channel("tweets:stream", {}) channel.join() .receive("ok", resp => { store.dispatch(setState(resp)) }) .receive("error", resp => { console.log("Unable to join", resp); })

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Channel infrastructure Phoenix Server Phoenix Server

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Phoenix Server Phoenix Server

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Phoenix Server Phoenix Server Clients Channels

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Phoenix Server Channel Channel

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Phoenix Server Repo Supervisor Channel Channel

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Phoenix Server Repo Supervisor Channel Channel

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Phoenix Server Repo Supervisor Channel

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Phoenix Server Repo Supervisor Channel Channel

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Phoenix Server Repo Supervisor Channel Channel TwitterClient

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defmodule Conflicted do use Application def start(_type, _args) do import Supervisor.Spec, warn: false children = [ supervisor(Conflicted.Endpoint, []), worker(Conflicted.Repo, []), worker(Task, [fn -> stream_task("elixirfriends") end]) ] opts = [strategy: :one_for_one, name: Conflicted.Supervisor] Supervisor.start_link(children, opts) end defp stream_task(term) do Conflicted.TweetStreamer.stream(term) |> Enum.to_list end end

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defmodule Conflicted.TweetStreamer do alias Conflicted.Repo import Ecto.Query, only: [from: 2] def stream(search_term) do ExTwitter.stream_filter(track: search_term) |> Stream.filter(&has_images?/1) |> Stream.filter(&new_tweet?/1) |> Stream.map(&store_tweet/1) end defp store_tweet(raw_tweet) do tweet = raw_tweet |> new_tweet |> Repo.insert! |> IO.inspect Conflicted.Endpoint.broadcast!("tweets:stream", "state", tweet) end # … end

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def stream(search_term) do ExTwitter.stream_filter(track: search_term) |> Stream.filter(&has_images?/1) |> Stream.filter(&new_tweet?/1) |> Stream.map(&store_tweet/1) end

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def stream(search_term) do ExTwitter.stream_filter(track: search_term) |> Stream.filter(&has_images?/1) |> Stream.filter(&new_tweet?/1) |> Stream.map(&store_tweet/1) end defp store_tweet(raw_tweet) do tweet = raw_tweet |> new_tweet |> Repo.insert! |> IO.inspect Conflicted.Endpoint.broadcast!("tweets:stream", "state", tweet) end

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channel.on("state", tweet => { store.dispatch(setState([tweet])) })

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Lets build an app Controllers & Channels Models Supervisor Trees Changesets

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export function setState(state) { return { type: SET_STATE, state } } export function likeTweet(id) { return { meta: {remote: true}, type: LIKE_TWEET, id } }

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export default channel => store => next => action => { if (action.meta && action.meta.remote) channel.push('action', action) return next(action) }

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import { Map } from 'immutable' import { SET_STATE, LIKE_TWEET } from '../actions' const setState = (state, newState) => { let tweets = newState.map((tweet) => [tweet.id, tweet]) return state.merge(tweets) } const likeTweet = (state, id) => { return state.updateIn([id, 'likes'], val => val + 1) } export default function tweetsReducer(state=Map({}), action) { switch(action.type) { case SET_STATE: return setState(state, action.state) case LIKE_TWEET: return likeTweet(state, action.id) default: return state } }

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def handle_in("action", %{"type" => "LIKE_TWEET", "id" => id}, socket) do changeset = Tweet |> Repo.get!(id) |> Tweet.changeset(%{"likes" => tweet.likes+1}) case Repo.update(changeset) do {:ok, tweet} -> broadcast!(socket, "state", tweet) {:error, changeset} -> IO.puts "SOMETHING WENT WRONG" IO.inspect changeset end {:noreply, socket} end

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Pattern match on the action def handle_in("action", %{"type" => "LIKE_TWEET", "id" => id}, socket) do changeset = Tweet |> Repo.get!(id) |> Tweet.changeset(%{"likes" => tweet.likes+1}) case Repo.update(changeset) do {:ok, tweet} -> broadcast!(socket, "state", tweet) {:error, changeset} -> IO.puts "SOMETHING WENT WRONG" IO.inspect changeset end {:noreply, socket} end

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Increment the likes by 1 Pattern match on the action def handle_in("action", %{"type" => "LIKE_TWEET", "id" => id}, socket) do changeset = Tweet |> Repo.get!(id) |> Tweet.changeset(%{"likes" => tweet.likes+1}) case Repo.update(changeset) do {:ok, tweet} -> broadcast!(socket, "state", tweet) {:error, changeset} -> IO.puts "SOMETHING WENT WRONG" IO.inspect changeset end {:noreply, socket} end

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Increment the likes by 1 Send a message back to all of the clients Pattern match on the action def handle_in("action", %{"type" => "LIKE_TWEET", "id" => id}, socket) do changeset = Tweet |> Repo.get!(id) |> Tweet.changeset(%{"likes" => tweet.likes+1}) case Repo.update(changeset) do {:ok, tweet} -> broadcast!(socket, "state", tweet) {:error, changeset} -> IO.puts "SOMETHING WENT WRONG" IO.inspect changeset end {:noreply, socket} end

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defmodule Conflicted.Tweet do use Conflicted.Web, :model schema "tweets" do field :author, :string field :content, :string field :source_url, :string field :image_url, :string field :likes, :integer, default: 0 timestamps end @required_fields ~w(author content source_url image_url) @optional_fields ~w(likes) def changeset(model, params \\ []) do model |> cast(params, @required_fields, @optional_fields) |> validate_number(:likes, greater_than_or_equal_to: 0) end end

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@required_fields ~w(author content source_url image_url) @optional_fields ~w(likes) def changeset(model, params \\ []) do model |> cast(params, @required_fields, @optional_fields) |> validate_number(:likes, greater_than_or_equal_to: 0) end Transform into changeset

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Create a changeset def handle_in("action", %{"type" => "LIKE_TWEET", "id" => id}, socket) do changeset = Tweet |> Repo.get!(id) |> Tweet.changeset(%{"likes" => tweet.likes+1}) case Repo.update(changeset) do {:ok, tweet} -> broadcast!(socket, "state", tweet) {:error, changeset} -> IO.puts "SOMETHING WENT WRONG" IO.inspect changeset end {:noreply, socket} end Execute the change

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So much more!

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Web Android Windows (C#) iOS

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Monitoring

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Getting started • http://elixir-lang.org/ • http://www.phoenixframework.org/docs/installation • http://www.phoenixframework.org/ • https://github.com/keathley/conﬂicted

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Thanks @Chris Keathley / keathley@carbonﬁve.com / keathley.io