Only possible with Elixir - ubots Case Study

How to build four successful products with a tiny team of two working part-time after-hours? The answer is: Elixir.

- What are Slack Bots and why you should care
- How we decided on our architecture and what were the consequences
- How we've built a new framework using old ideas
- How we've built an end-to-end testing framework for complex interactions

Transcript

2. Only possible with Elixir UBOTS Case Study
3. My name is Tymon Tobolski. I'm the one behind tesla HTTP library. Co-founder of UBOTS - Useful bots for Slack @teamon @ GitHub @iteamon @ Twitter
4. Ruby ➡ Elixir (ASM, C, PHP, Java, Scala, Haskell, JavaScript, Go, Infra, ...)
5. How to build something exclusively with Elixir?
8. UI = JSON ‑ ‑ ‑ ! =
10. Adam ! Development @ Ubots Head of Integrations @ Recruitee Kamil Marketing @ Ubots SRE @ Cabify
11. Why we succeeded?
12. Why we succeeded? We didn't quit our jobs We didn't move to Silicon Valley We didn't take VC money
13. Why we succeeded? We did charge $$$ from day one We chose Elixir
14. Developer Productivity
15. Elixir is Extremely Stable
16. Seamless Updates 1.9 ➡ 1.10 ➡ 1.11
17. Best Tooling mix, hex, dialyzer, formatter phoenix live reload, mix test.watch ElixirLS
18. !! != One Git repository One OTP application One Erlang release One Docker image + Two Developers ------------------------------ One Majestic Monolith
19. Top-Level Modules lib !"" core/ !"" core.ex !"" core_web/ !"" core_web.ex Core CoreWeb lib !"" bdgt/ !"" bdgt.ex !"" lunch/ !"" lunch.ex Bdgt Lunch lib !"" queue/ !"" queue.ex !"" td/ #"" td.ex Queue Td
20. This must be slow lib/ 21.000 LOC $ time mix compile Compiling 277 files (.ex) real 0m34.552s test/ 10.000 LOC $ mix test Finished in 17.1 seconds 18 doctests, 483 tests
21. the BORING stack
22. Old Patterns New "Framework"
23. HTTP POST /events content-type: application/json { "payload": { "user_id": "U123", "team_id": "T456" "command": "/help" } } --- POST /events content-type: text/form-urlencoded user_id=U123&team_id=T456&command=/help Core.Bot %Context{ user_id: "U123", team_id: "T456", responses: [...] ... } # Actions %Command{ command: "/queue", text: "help" } %Button{value: "join"} %Shortcut{...} ...
24. Ubots Slack "Framework" Web App Slack App Plug.Conn Context Struct params Action Structs Plug Middleware Phoenix.Router (Pattern Matching) Phoenix.Controller Controller Phoenix.View View
25. Pure Functional Code
26. View (pure function) defmodule Queue.Views.ModalConfig do def render(queue) do %{ type: "modal", blocks: [...] } end end
27. Impure Functional Code (side effects are cool)
28. Middleware (impure function) defmodule Core.Bot.Middleware.Logger do def call(ctx, action) do Logger.info(...) ctx end end
29. Pattern Matching
30. Pattern Matching in Actions ( ) def build(%{ "command" => command, "text" => text }) do %Command{command: command, text: text} end def build(%{ "type" => "shortcut", "callback_id" => callback_id }) do %Shortcut{callback_id: callback_id} end def build(%{ "type" => "view_submission", "view" => %{ "callback_id" => callback_id, "external_id" => external_id, "state" => %{"values" => values} } }) do %Submit{ callback_id: callback_id, external_id: decode_external_id(external_id), values: decode_values(values) } end
31. Pattern Matching in Controllers defmodule Queue.Controllers.Main do use Core.Bot.Controller def call(ctx, %Button{action_id: "button_join"}), do: # ... def call(ctx, %Command{text: "join"}), do: # ... def call(ctx, %Button{action_id: "button_leave"}), do: # ... def call(ctx, %Command{text: "leave"}), do: # ...
32. Macros (just some drops)
33. Macros for Controller Pipelines defmodule Queue do use Core.Bot.Controller plug Core.Bot.Middleware.Logger plug Core.Bot.Middleware.Ignorables plug Core.Bot.Middleware.Duplicates plug Core.Bot.Middleware.Support plug Queue.Controllers.Main plug Queue.Controllers.Home plug Queue.Controllers.Workflows # ...
34. Macros for DRY defmodule Core.Bot.Actions do use Core.Bot.ActionsBuilder defaction(Button, action_id: binary, value: binary ) defaction(Datepicker, action_id: binary, action_ts: binary, block_id: binary, initial_date: binary | nil, selected_date: binary )
35. Processes & OTP
36. Phoenix, Oban, ... got your back
37. Unleashing the full potential setup do [ alice: Slack.user(), dev: Slack.channel() ] end test "/queue", %{alice: alice, dev: dev} do alice |> go_to_channel(dev) |> command("/queue") |> click_button("Join") assert visible?(dev, "People in queue") end
38. Unleashing the full potential
39. Refactoring
40. Lax.Server (Single GenSever) defmodule Lax.Server do use GenServer # ... def handle_call({:get_channel, channel_id}, from, state) do handle_reply(Lax.State.get_channel(state, channel_id), from) end def handle_call({:access, action}, from, state) do handle_reply(Lax.Access.on(action, state), from) end def handle_call({:ui, action}, from, state) do handle_reply(Lax.UI.on(action, state), from) end def handle_call({:outgoing, ...}) do handle_reply(Lax.API.on(method, body, state), from) end # ... end ... The chery on top of all elixir features is the amazing community
41. Friendly Community & Smart People
42. Is this really only possible with Elixir?
43. 10 out of 10 boxes say: YES! ✅ Tooling ✅ Stability ✅ Readability ✅ Productivity ✅ Developer Experience ✅ Rich ecosystem ✅ Performance ✅ Scalability ✅ Community ✅ Great choice for business
44. ! Q & A ! Visit ubots.xyz for Useful Slack Bots ! Sign up at moonhome.io for the Future of Remote Development ! Follow @iteamon on Twitter to stay up-to-date