Hexagonal architecture & Elixir
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The document discusses hexagonal architecture and domain-driven design in Elixir, emphasizing the separation of business logic (domain) from technical details (infrastructure) to create maintainable software. It highlights the importance of using interfaces and behaviors, illustrating implementation with Elixir code snippets to demonstrate how to structure applications effectively. Additionally, it raises questions about the readability and testability of business logic while advocating for flexibility in infrastructure integration.
![def prs_open_time_until_today() do
today = Date.utc_today() !|> Date.to_iso8601()
{200, prs, _} =
Tentacat.Client.new(%{access_token: @access_token})
!|> Tentacat.Pulls.list("nicoespeon", "my-repo")
prs
!|> Enum.map(fn pr !-> pr["created_at"] end)
!|> Enum.flat_map(fn created_at !->
case DaysDiff.between(today, created_at) do
{:ok, open_time} !-> [open_time]
{:error, _} !-> []
end
end)
end](https://image.slidesharecdn.com/hexagonalarchitectureelixir-181120020628/85/Hexagonal-architecture-Elixir-14-320.jpg)
![def prs_open_time_until_today() do
today = Date.utc_today() !|> Date.to_iso8601()
{200, prs, _} =
Tentacat.Client.new(%{access_token: @access_token})
!|> Tentacat.Pulls.list("nicoespeon", "my-repo")
prs
!|> Enum.map(fn pr !-> pr["created_at"] end)
!|> Enum.flat_map(fn created_at !->
case DaysDiff.between(today, created_at) do
{:ok, open_time} !-> [open_time]
{:error, _} !-> []
end
end)
end](https://image.slidesharecdn.com/hexagonalarchitectureelixir-181120020628/85/Hexagonal-architecture-Elixir-15-320.jpg)
![# i_read_prs.ex (Behavior)
defmodule IReadPrs do
@callback opened_prs() !:: [OpenTime.pr()]
end
# i_give_dates.ex (Behavior)
defmodule IGiveDates do
@callback today() !:: String.t()
end](https://image.slidesharecdn.com/hexagonalarchitectureelixir-181120020628/85/Hexagonal-architecture-Elixir-39-320.jpg)
![defmodule OpenTime do
@type pr !:: %{created_at: String.t()}
@dates_giver Application.get_env(:pr_metrics, :dates_giver)
@prs_reader Application.get_env(:pr_metrics, :prs_reader)
def prs_open_time_until_today() do
today = @dates_giver.today()
prs = @prs_reader.opened_prs()
prs
!|> Enum.map(fn pr !-> pr.created_at end)
!|> Enum.flat_map(fn created_at !->
case DaysDiff.between(today, created_at) do
{:ok, open_time} !-> [open_time]
{:error, _} !-> []
end
end)
end
end](https://image.slidesharecdn.com/hexagonalarchitectureelixir-181120020628/85/Hexagonal-architecture-Elixir-43-320.jpg)
![# dates_giver.system.ex (Adapter)
defmodule DatesGiver.System do
@behaviour IGiveDates
def today, do: Date.utc_today() !|> Date.to_iso8601()
end
# prs_reader.github.ex (Adapter)
defmodule PrsReader.GitHub do
@behaviour IReadPrs
@access_token Application.get_env(:pr_metrics, :github_access_token)
def opened_prs do
{200, prs, _} =
Tentacat.Client.new(%{access_token: @access_token})
!|> Tentacat.Pulls.list("nicoespeon", "my-repo")
prs
!|> Enum.map(fn pr !-> %{created_at: pr["created_at"]} end)
end
end](https://image.slidesharecdn.com/hexagonalarchitectureelixir-181120020628/85/Hexagonal-architecture-Elixir-46-320.jpg)
![defmodule OpenTimeTest do
use ExUnit.Case
import Mox
test "returns an empty array if there is no opened PR" do
open_times = OpenTime.prs_open_time_until_today()
assert open_times !== []
end
end](https://image.slidesharecdn.com/hexagonalarchitectureelixir-181120020628/85/Hexagonal-architecture-Elixir-50-320.jpg)
![defmodule OpenTimeTest do
use ExUnit.Case
import Mox
@today "2011-01-10"
test "returns an empty array if there is no opened PR" do
Mock.DatesGiver
!|> stub(:today, fn !-> @today end)
open_times = OpenTime.prs_open_time_until_today()
assert open_times !== []
end
end](https://image.slidesharecdn.com/hexagonalarchitectureelixir-181120020628/85/Hexagonal-architecture-Elixir-51-320.jpg)
![defmodule OpenTimeTest do
use ExUnit.Case
import Mox
@today "2011-01-10"
test "returns an empty array if there is no opened PR" do
Mock.DatesGiver
!|> stub(:today, fn !-> @today end)
Mock.PrsReader
!|> stub(:opened_prs, fn !-> [] end)
open_times = OpenTime.prs_open_time_until_today()
assert open_times !== []
end
end](https://image.slidesharecdn.com/hexagonalarchitectureelixir-181120020628/85/Hexagonal-architecture-Elixir-52-320.jpg)
Hexagonal architecture & Elixir
- 2. Buzzwords 🐝
- 4. Lots of Buzzwords This is not about them…
- 5. Separate Domain & Infrastructure = maintainable software
- 6. @nicoespeon
- 9. Software is a mean to a Business end
- 11. Business doesn't care! Infrastructure can change shouldn't
- 12. Can your PM 🌟 understand 🌟 the source code?
- 13. Problems mixing Domain & Infra.
- 14. def prs_open_time_until_today() do today = Date.utc_today() !|> Date.to_iso8601() {200, prs, _} = Tentacat.Client.new(%{access_token: @access_token}) !|> Tentacat.Pulls.list("nicoespeon", "my-repo") prs !|> Enum.map(fn pr !-> pr["created_at"] end) !|> Enum.flat_map(fn created_at !-> case DaysDiff.between(today, created_at) do {:ok, open_time} !-> [open_time] {:error, _} !-> [] end end) end
- 15. def prs_open_time_until_today() do today = Date.utc_today() !|> Date.to_iso8601() {200, prs, _} = Tentacat.Client.new(%{access_token: @access_token}) !|> Tentacat.Pulls.list("nicoespeon", "my-repo") prs !|> Enum.map(fn pr !-> pr["created_at"] end) !|> Enum.flat_map(fn created_at !-> case DaysDiff.between(today, created_at) do {:ok, open_time} !-> [open_time] {:error, _} !-> [] end end) end
- 16. Hard to see the Business
- 17. Hard to test the Business
- 18. Hard to change the Business
- 19. Hard to change the Infra. without breaking the Business
- 20. Is your Business easy to read? 📖
- 21. Is your Business easy to test? 🚦
- 23. The simplest way to Separate Domain & Infrastructure
- 24. Infra. Domain
- 25. The outside depends on the inside. Never the opposite. Rule
- 30. Inside the Hexagon Business language only
- 32. '(Benefits
- 33. Flexibility REST API CLI CRON FTP File System HTTP Console Sentry Postgres …
- 34. You can plug another Infra. to the Domain 🔌
- 35. A good software architect defers technical decisions
- 36. You can start with something simple✨
- 37. In Elixir
- 38. Interfaces in Elixir But we have Behaviours
- 39. # i_read_prs.ex (Behavior) defmodule IReadPrs do @callback opened_prs() !:: [OpenTime.pr()] end # i_give_dates.ex (Behavior) defmodule IGiveDates do @callback today() !:: String.t() end
- 40. defmodule OpenTime do @type pr !:: %{created_at: String.t()} def prs_open_time_until_today() do end end
- 41. defmodule OpenTime do @type pr !:: %{created_at: String.t()} @dates_giver Application.get_env(:pr_metrics, :dates_giver) def prs_open_time_until_today() do today = @dates_giver.today() end end
- 42. defmodule OpenTime do @type pr !:: %{created_at: String.t()} @dates_giver Application.get_env(:pr_metrics, :dates_giver) @prs_reader Application.get_env(:pr_metrics, :prs_reader) def prs_open_time_until_today() do today = @dates_giver.today() prs = @prs_reader.opened_prs() end end
- 43. defmodule OpenTime do @type pr !:: %{created_at: String.t()} @dates_giver Application.get_env(:pr_metrics, :dates_giver) @prs_reader Application.get_env(:pr_metrics, :prs_reader) def prs_open_time_until_today() do today = @dates_giver.today() prs = @prs_reader.opened_prs() prs !|> Enum.map(fn pr !-> pr.created_at end) !|> Enum.flat_map(fn created_at !-> case DaysDiff.between(today, created_at) do {:ok, open_time} !-> [open_time] {:error, _} !-> [] end end) end end
- 44. # dates_giver.system.ex (Adapter) defmodule DatesGiver.System do @behaviour IGiveDates end # prs_reader.github.ex (Adapter) defmodule PrsReader.GitHub do @behaviour IReadPrs end
- 45. # dates_giver.system.ex (Adapter) defmodule DatesGiver.System do @behaviour IGiveDates def today, do: Date.utc_today() !|> Date.to_iso8601() end # prs_reader.github.ex (Adapter) defmodule PrsReader.GitHub do @behaviour IReadPrs end
- 46. # dates_giver.system.ex (Adapter) defmodule DatesGiver.System do @behaviour IGiveDates def today, do: Date.utc_today() !|> Date.to_iso8601() end # prs_reader.github.ex (Adapter) defmodule PrsReader.GitHub do @behaviour IReadPrs @access_token Application.get_env(:pr_metrics, :github_access_token) def opened_prs do {200, prs, _} = Tentacat.Client.new(%{access_token: @access_token}) !|> Tentacat.Pulls.list("nicoespeon", "my-repo") prs !|> Enum.map(fn pr !-> %{created_at: pr["created_at"]} end) end end
- 47. # config/config.exs use Mix.Config config :pr_metrics, dates_giver: DatesGiver.System, prs_reader: PrsReader.GitHub
- 48. # config/config.test.exs use Mix.Config config :pr_metrics, dates_giver: Mock.DatesGiver, prs_reader: Mock.PrsReader
- 49. defmodule OpenTimeTest do use ExUnit.Case import Mox end
- 50. defmodule OpenTimeTest do use ExUnit.Case import Mox test "returns an empty array if there is no opened PR" do open_times = OpenTime.prs_open_time_until_today() assert open_times !== [] end end
- 51. defmodule OpenTimeTest do use ExUnit.Case import Mox @today "2011-01-10" test "returns an empty array if there is no opened PR" do Mock.DatesGiver !|> stub(:today, fn !-> @today end) open_times = OpenTime.prs_open_time_until_today() assert open_times !== [] end end
- 52. defmodule OpenTimeTest do use ExUnit.Case import Mox @today "2011-01-10" test "returns an empty array if there is no opened PR" do Mock.DatesGiver !|> stub(:today, fn !-> @today end) Mock.PrsReader !|> stub(:opened_prs, fn !-> [] end) open_times = OpenTime.prs_open_time_until_today() assert open_times !== [] end end
- 54. Use Domain language in Behaviours
- 55. + Limits,
- 56. It doesn't guide you to scale 🚀
- 58. Compatible Ubiquitous Language Bounded Contexts Domain modelling