Real-Time applications in Phoenix

A talk about building real time applications in phoenix and elixir with examples for both the client side and server side.

Transcript

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

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

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3. Lets talk about
   Realtime
   

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4. Rails + Faye
   

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5. Rails
   Faye
   

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6. Node + socket.io
   

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7. socket.io
   socket.io
   Redis
   

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8. Complexity
   

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9. Balance
   

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11. 2 million connections per server
    

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12. 2 million connections per server
    400 million users
    

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13. 2 million connections per server
    400 million users
    30 Engineers
    

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14. Erlang
    

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15. Heroku
    RabbitMQ
    Riak
    Facebook
    

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16. Elixir
    

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17. 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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18. Pattern Matching
    iex(1)> x = 3
    3
    

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

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

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21. Pattern Matching is
    an assertion
    

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22. Pattern Matching
    iex(3)> 3 = x
    3
    

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23. 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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24. Immutability
    

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

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26. 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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27. Processes
    C# Thread: 4Mb
    

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

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

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30. OTP
    GenServer
    Supervisors
    GenFSM
    GenEvent
    Observer
    Dialyzer
    

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31. Let It Crash
    

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33. ❤
    Real-time
    

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

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35. Demo
    http://bit.ly/1OEWVQ2
    

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36. Lets build an app
    Controllers & Channels
    Models
    Supervisor Trees
    Changesets
    

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37. Lets build an app
    Controllers & Channels
    Models
    Supervisor Trees
    Changesets
    

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

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

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

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

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

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

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

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

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

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50. 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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51. 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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52. def join("tweets:stream", _message, socket) do
    tweets = Repo.all(Tweet)
    {:ok, tweets, socket}
    end
    

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53. 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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54. Lets build an app
    Controllers & Channels
    Models
    Supervisor Trees
    Changesets
    

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55. 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
    end
    

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56. DB
    Repo
    Query
    Data
    

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57. 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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58. 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
    

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59. Lets build an app
    Controllers & Channels
    Models
    Supervisor Trees
    Changesets
    

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60. 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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61. Channel infrastructure
    Phoenix Server
    Phoenix Server
    

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62. Phoenix Server
    Phoenix Server
    

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63. Phoenix Server
    Phoenix Server
    Clients Channels
    

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64. Phoenix Server
    Channel Channel
    

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65. Phoenix Server Repo
    Supervisor
    Channel Channel
    

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66. Phoenix Server Repo
    Supervisor
    Channel Channel
    

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67. Phoenix Server Repo
    Supervisor
    Channel
    

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68. Phoenix Server Repo
    Supervisor
    Channel Channel
    

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69. Phoenix Server Repo
    Supervisor
    Channel Channel
    TwitterClient
    

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70. 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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71. 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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72. 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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73. 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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74. channel.on("state", tweet => {
    store.dispatch(setState([tweet]))
    })
    

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75. Lets build an app
    Controllers & Channels
    Models
    Supervisor Trees
    Changesets
    

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

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78. 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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79. 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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80. 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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81. 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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82. 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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83. 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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84. @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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85. @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
    Provide some validation
    

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86. 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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87. 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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88. 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
    Handle the response
    

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89. So much more!
    

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90. Web
    Android
    Windows (C#)
    iOS
    

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91. Monitoring
    

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

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