Elixir, your Monolith 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.

Join us on our tale of adopting Elixir and Phoenix and see what we learned, what we loved, and what bumps we hit along the road

Transcript

1. Who wants to go and build a system in Elixir?
5. Can't go out and rewrite it all
6. You shouldn’t
7. Elixir, your Monolith and You (alpha-1) Tobias Pfeiffer @PragTob pragtob.info
8. Your Monolith and You
10. Your Monolith now?
11. Your Monolith?
12. Tear it all down and rewrite it
14. Sooooon!
15. “We rewrote it all in Language x, now it’s 10 times faster and only 50% of the code!” Someone
16. “Language x, is 10 times faster and requires 50% of the code of language Y!” Someone Often implies...
17. What nobody tells you...
18. Business Value?
19. Sooooon!
20. Replace it step by step
21. We have a bedroom, for the bathroom please check out legacy!
22. Terraform allows you to incrementally transform an older API into one powered by Phoenix - one endpoint at a time. poteto/terraform
23. 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
24. Replace a critical component
25. Check out our sweet new heating system!
26. Write a new component
27. Check it out we built a brand new high tech entertainment facility!
28. Write a new component Obvious in microservices
29. “Is the technology I’m choosing the right fit for the problem I’m trying to solve?” Everyone, hopefully
30. Reasonably separate and limited problem
31. Requirement that poses a problem for the current stack
32. Spark of Enthusiasm
33. Courier Tracking
34. Courier Tracking
35. Courier Tracking
36. Courier Tracking Websockets
37. Courier Tracking Websockets Basic Knowledge
38. How to make them talk?
39. Monolith Frontend Courier DB
40. Monolith Tracking Frontend Courier DB DB
41. Connect them?
42. Monolith Tracking Frontend Courier DB DB
43. JSON Web Token
44. Header Payload Signature
45. { "role": "admin", "courier_ids": [1337, 55], "id": 42, "exp": 1520469475 }
46. Monolith Tracking Frontend Courier DB DB Shared Secret
47. Monolith Tracking Frontend Courier DB DB JWT JWT Shared Secret
48. Monolith Tracking Frontend Courier DB DB JWT JWT JWT Shared Secret JWT
49. def connect(%{"token" => token}, socket) do token |> JWT.verify_token |> respond_based_on_token_contents(socket) end Socket
50. defp login_user(%{"role" => role, ...}, socket) do {:ok, assign(socket, :user, %{role: role, ...})} end Socket
51. def join("courier:" <> courier_id, _, % {assigns: %{user: user}}) do if authorized?(courier_id, user) do # login else # unauthorizd end end Channel
52. 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
53. Monolith Tracking Frontend Courier DB DB Locations Locations Most of the time
54. Fulfillment
55. Fulfillment CRUD
56. Fulfillment CRUD Experience
57. Monolith Fulfillment DB DB
58. Monolith Fulfillment DB DB Own UI
59. Monolith Fulfillment DB DB OAuth OAuth
60. Monolith Fulfillment DB DB /current_user Who?
61. Monolith Fulfillment DB DB Products
62. Monolith Fulfillment DB DB Order Valid? Order
63. Monolith Fulfillment DB DB Packaging Create
64. Rail-way oriented programming!
65. Railway Oriented Programming
66. 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
67. 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
68. 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
69. 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
70. 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
71. 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
72. No Kafka/Message Queue?
73. Be careful with new technologies!
74. Microservices!
75. Microservices! ”Macroapplications”
76. All challenges are clearly technical
77. All challenges are clearly technical
78. Stakeholders
79. Your team
80. First Major Version
81. Get the others on board
82. Workshops
83. To know it, you got to build it
85. Pair Adopter with Alchemist
86. Pair Adopter with Alchemist Alchemist doesn’t touch keyboard
87. Knowledge
88. Knowledge
89. “We are still using this like Rails – we should use GenServers!” Someone on your team
90. You don’t need to kill your Monolith, Complement it
91. Your Apps
92. Enjoy using Elixir effectively to help your company Tobias Pfeiffer @PragTob pragtob.info