Your Monolith, Elixir and You

Elixir is great, so clearly we'll all rewrite our applications in Elixir. Mostly, you can't and shouldn't do that. This presentation will show you another path. You’ll see how at Liefery, we started with small steps instead of rewriting everything. This allowed us to reap the benefits earlier and get comfortable before getting deeper into it. We’ll examine in detail the tactics we used to create two Elixir apps for new requirements, and how we integrated them with our existing Rails code base.

Transcript

1. View Slide

2. functional
   

   View Slide

3. functional
   ErlangVM
   

   View Slide

4. functional
   ErlangVM
   Parallelism
   

   View Slide

5. Who wants to go and
   build a system in Elixir?
   

   View Slide

6. View Slide

7. View Slide

8. View Slide

9. View Slide

10. You shouldn’t
    

    View Slide

11. Elixir, Your Monolith and You
    Tobias Pfeiffer
    @PragTob
    pragtob.info
    

    View Slide

12. Your Monolith and You
    

    View Slide

13. View Slide

14. Your Monolith now?
    

    View Slide

15. Your Monolith?
    

    View Slide

16. Tear it all down and
    rewrite it
    

    View Slide

17. View Slide

18. Sooooon!
    

    View Slide

19. “We rewrote it all in
    Language x, now it’s 10
    times faster and only
    50% of the code!”
    Someone
    

    View Slide

20. “Language x, is 10 times
    faster and requires 50% of
    the code of language Y!”
    Someone
    Often implies...
    

    View Slide

21. What nobody tells you...
    

    View Slide

22. Business Value?
    

    View Slide

23. Sooooon!
    

    View Slide

24. Replace it step by step
    

    View Slide

25. We have a bedroom,
    for the bathroom please
    check out legacy!
    

    View Slide

26. Terraform allows you to
    incrementally transform an
    older API into one powered by
    Phoenix - one endpoint at a
    time.
    poteto/terraform
    

    View Slide

27. Terraform allows you to
    incrementally transform an
    older API into one powered by
    Phoenix - one endpoint at a
    time.
    poteto/terraform
    Not the Infrastructure
    As Code
    

    View Slide

28. defmodule MyApp.Terraformers.Foo do
    alias MyApp.Clients.Foo
    use Plug.Router
    plug :match
    plug :dispatch
    get "/v1/hello-world", do: send_resp(conn, 200, "Hi")
    get _ do
    res = Foo.get!(conn)
    send_response({:ok, conn, res})
    end
    end
    poteto/terraform
    

    View Slide

29. Replace a critical
    component
    

    View Slide

30. Damn our heater always
    breaks down when it’s cold!
    

    View Slide

31. Check out our sweet new
    heating system!
    

    View Slide

32. Write a new component
    

    View Slide

33. Check it out we built a
    brand new high tech
    entertainment facility!
    

    View Slide

34. Write a new component
    Obvious in microservices
    

    View Slide

35. “Is the technology I’m
    choosing the right fit for
    the problem I’m trying to
    solve?”
    Everyone, hopefully
    

    View Slide

36. Reasonably separate and
    limited problem
    

    View Slide

37. Requirement that poses a
    problem for the current
    stack
    

    View Slide

38. Spark of Enthusiasm
    

    View Slide

39. Courier Tracking
    

    View Slide

40. Courier Tracking
    

    View Slide

41. Courier Tracking
    

    View Slide

42. Courier Tracking
    Websockets
    

    View Slide

43. Courier Tracking
    Websockets
    Basic Knowledge
    

    View Slide

44. How to make them talk?
    

    View Slide

45. Monolith
    Frontend
    Courier
    DB
    

    View Slide

46. Monolith
    Tracking
    Frontend
    Courier
    DB DB
    

    View Slide

47. Connect them?
    

    View Slide

48. Monolith
    Tracking
    Frontend
    Courier
    DB DB
    

    View Slide

49. JSON
    Web
    Token
    

    View Slide

50. Header
    Payload
    Signature
    

    View Slide

51. {
    "role": "admin",
    "courier_ids": [1337, 55],
    "id": 42,
    "exp": 1520469475
    }
    

    View Slide

52. Monolith
    Tracking
    Frontend
    Courier
    DB DB
    Shared Secret
    

    View Slide

53. Monolith
    Tracking
    Frontend
    Courier
    DB DB
    JWT
    JWT
    Shared Secret
    

    View Slide

54. Monolith
    Tracking
    Frontend
    Courier
    DB DB
    JWT
    JWT
    JWT
    Shared Secret
    JWT
    

    View Slide

55. def connect(%{"token" => token}, socket) do
    token
    |> JWT.verify_token
    |> respond_based_on_token_contents(socket)
    end
    Socket
    

    View Slide

56. def connect(%{"token" => token}, socket) do
    token
    |> JWT.verify_token
    |> respond_based_on_token_contents(socket)
    end
    Pattern Match
    

    View Slide

57. def connect(%{"token" => token}, socket) do
    token
    |> JWT.verify_token
    |> respond_based_on_token_contents(socket)
    end
    Pipe
    

    View Slide

58. defp login_user(%{"role" => role, ...}, socket) do
    {:ok, assign(socket, :user, %{role: role, ...})}
    end
    Socket
    

    View Slide

59. def join("courier:" <> courier_id, _,
    %{assigns: %{user: user}}) do
    if authorized?(courier_id, user) do
    # login
    else
    # unauthorizd
    end
    end
    Channel
    

    View Slide

60. defp authorized?("", _), do: false
    defp authorized?(courier_id, %{courier_ids: ids}) do
    Enum.member?(ids, String.to_integer(courier_id))
    end
    defp authorized?(_, _), do: false
    Channel
    

    View Slide

61. defp authorized?("", _), do: false
    defp authorized?(courier_id, %{courier_ids: ids}) do
    Enum.member?(ids, String.to_integer(courier_id))
    end
    defp authorized?(_, _), do: false
    Channel
    

    View Slide

62. defp authorized?("", _), do: false
    defp authorized?(courier_id, %{courier_ids: ids}) do
    Enum.member?(ids, String.to_integer(courier_id))
    end
    defp authorized?(_, _), do: false
    Channel
    

    View Slide

63. defp authorized?("", _), do: false
    defp authorized?(courier_id, %{courier_ids: ids}) do
    Enum.member?(ids, String.to_integer(courier_id))
    end
    defp authorized?(_, _), do: false
    Channel
    

    View Slide

64. defp authorized?("", _), do: false
    defp authorized?(courier_id, %{courier_ids: ids}) do
    Enum.member?(ids, String.to_integer(courier_id))
    end
    defp authorized?(_, _), do: false
    Channel
    

    View Slide

65. Monolith
    Tracking
    Frontend
    Courier
    DB DB
    Locations
    Locations
    Most of the time
    

    View Slide

66. Monolith
    Tracking
    Frontend
    Courier
    DB DB
    Locations
    Locations
    Websocket
    

    View Slide

67. Monolith
    Tracking
    Frontend
    Courier
    DB DB
    Locations
    Locations
    HTTP REST
    

    View Slide

68. Fulfillment
    

    View Slide

69. Fulfillment
    CRUD
    

    View Slide

70. Fulfillment
    CRUD
    Experience
    

    View Slide

71. Monolith
    Fulfillment
    DB DB
    

    View Slide

72. Monolith
    Fulfillment
    DB DB
    Own UI
    

    View Slide

73. Monolith
    Fulfillment
    DB DB
    OAuth
    OAuth
    

    View Slide

74. Monolith
    Fulfillment
    DB DB
    /current_user
    Who?
    

    View Slide

75. Monolith
    Fulfillment
    DB DB
    Products
    

    View Slide

76. Monolith
    Fulfillment
    DB DB
    Order
    Valid?
    Order
    

    View Slide

77. Monolith
    Fulfillment
    DB DB
    Packaging
    Create
    

    View Slide

78. Monolith
    Fulfillment
    DB DB
    HTTP REST
    Create
    

    View Slide

79. Railway Oriented Programming
    

    View Slide

80. defmodule Fulfillment.OrderCreation do
    def create(params, customer, auth) do
    with {:ok, order} <- validate_order(params, customer),
    {:ok, order} <- validate_in_backend(order, auth),
    {:ok, order} <- Repo.insert(order) do
    {:ok, order}
    else
    {:error, changeset} -> {:error, changeset}
    end
    end
    end
    

    View Slide

81. defmodule Fulfillment.OrderCreation do
    def create(params, customer, auth) do
    with {:ok, order} <- validate_order(params, customer),
    {:ok, order} <- validate_in_backend(order, auth),
    {:ok, order} <- Repo.insert(order) do
    {:ok, order}
    else
    {:error, changeset} -> {:error, changeset}
    end
    end
    end
    “Success” Rail
    

    View Slide

82. defmodule Fulfillment.OrderCreation do
    def create(params, customer, auth) do
    with {:ok, order} <- validate_order(params, customer),
    {:ok, order} <- validate_in_backend(order, auth),
    {:ok, order} <- Repo.insert(order) do
    {:ok, order}
    else
    {:error, changeset} -> {:error, changeset}
    end
    end
    end
    “Error” Rail
    

    View Slide

83. defmodule Fulfillment.OrderCreation do
    def create(params, customer, auth) do
    with {:ok, order} <- validate_order(params, customer),
    {:ok, order} <- validate_in_backend(order, auth),
    {:ok, order} <- Repo.insert(order) do
    {:ok, order}
    else
    {:error, changeset} -> {:error, changeset}
    end
    end
    end
    Validate internally
    

    View Slide

84. defmodule Fulfillment.OrderCreation do
    def create(params, customer, auth) do
    with {:ok, order} <- validate_order(params, customer),
    {:ok, order} <- validate_in_backend(order, auth),
    {:ok, order} <- Repo.insert(order) do
    {:ok, order}
    else
    {:error, changeset} -> {:error, changeset}
    end
    end
    end
    Validate externally
    

    View Slide

85. defmodule Fulfillment.OrderCreation do
    def create(params, customer, auth) do
    with {:ok, order} <- validate_order(params, customer),
    {:ok, order} <- validate_in_backend(order, auth),
    {:ok, order} <- Repo.insert(order) do
    {:ok, order}
    else
    {:error, changeset} -> {:error, changeset}
    end
    end
    end
    Save
    

    View Slide

86. defmodule Fulfillment.OrderCreation do
    def create(params, customer, auth) do
    with {:ok, order} <- validate_order(params, customer),
    {:ok, order} <- validate_in_backend(order, auth),
    {:ok, order} <- Repo.insert(order) do
    {:ok, order}
    else
    {:error, changeset} -> {:error, changeset}
    end
    end
    end
    Done
    

    View Slide

87. No Kafka/
    Message Queue/
    GraphQL?
    

    View Slide

88. Be careful with new
    technologies!
    

    View Slide

89. Microservices!
    

    View Slide

90. Microservices!
    ”Macroapplications”
    

    View Slide

91. All challenges are
    clearly technical
    

    View Slide

92. All challenges are
    clearly technical
    

    View Slide

93. Stakeholders
    

    View Slide

94. Your team
    

    View Slide

95. First Major Version
    

    View Slide

96. Get the others on board
    

    View Slide

97. Workshops
    

    View Slide

98. To know it,
    you got to build it
    

    View Slide

99. View Slide

100. Pair Adopter with Alchemist
     

     View Slide

101. Pair Adopter with Alchemist
     Alchemist doesn’t touch keyboard
     

     View Slide

102. Knowledge
     

     View Slide

103. Knowledge
     

     View Slide

104. “We are still using this
     like Rails – we should
     use GenServers!”
     Someone on your team
     

     View Slide

105. You don’t need to kill
     your Monolith,
     Complement it
     

     View Slide

106. Your Apps
     

     View Slide

107. Enjoy Using Elixir effectively to
     Help Your Company
     Tobias Pfeiffer
     @PragTob
     pragtob.info
     

     View Slide