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Chapter.11 Observer and Umbrellas

extracted umbrella app

  • channels & MVC components currently support user interfaces & directly communicate with biz backend

  • here these will refactored into child apps

Introspecting Applications with Observer

running Videologue starts multiple Applications alongside; Supervisors start/stop apps as unit using Supervision Tree details

  • can start :observer.start() at iex -S mix; it allows understanding running processes for app

  • in processes tab, ordering process by MsgQueue size might allow see the bottleneck

  • Applications tab show all applications & its Supervision Tree; it will miss the server since iex -S mix phx.server wasn't started

processes can be killed from here to check

  • moving to umbrella, can keep Web & Backend separate as separate Applications but in same repository without version issues

Using Umbrellas

  • each Umbrella project has a parent dir which contains apps dir & share config for projects

  • can use mix new videologue --umbrella; but let's mix phx.new videologue --umbrella as it will automate some web-based path & config generation

let's press n for dependency install; as we'll copy existing elixir and js code; we have videologue_umbrella project now

  • using phx.new ... --umbrella auto creates videologue_umbrella/apps/{videologue,videologue_web}
  • new created apps configuration would be like
def project do
  [
    app: :some_web,
    version: "0.1.0",
    build_path: "../../_build",
    config_path: "../../config/config.exs",
    deps_path: "../../deps",
    lockfile: "../../mix.lock",
    elixir: "~> 1.7",
    elixirc_paths: elixirc_paths(Mix.env()),
    compilers: [:phoenix, :gettext] ++ Mix.compilers(),
    start_permanent: Mix.env() == :prod,
    aliases: aliases(),
    deps: deps()
  ]
end

...

defp deps do
  [
    {:phoenix, "~> 1.5.9"},
    ...
    {:videologue, in_umbrella: true},
    ...
  ]
end

all children apps share same config & dependency; are isolate but ran on same VM

Extracting Videlogue and VideologueWeb

  • copy over content for videologue app
cp -R videologue/lib/videologue videologue_umbrella/apps/videologue/lib
cp videologue/lib/videologue.ex videologue_umbrella/apps/videologue/lib
cp -R videologue/test/videologue videologue_umbrella/apps/videologue/test
cp -R videologue/priv/repo videologue_umbrella/apps/videologue/priv
cp videologue/test/support/data_case.ex videologue_umbrella/apps/videologue/test/support
cp videologue/test/test_helper.exs videologue_umbrella/apps/videologue/test

update videologue_umbrella/videologue/application to have only Repo under children

    children = [
      Videologue.Repo,
    ]
  • copy content for videologue_web app
cp -R videologue/lib/videologue_web videologue_umbrella/apps/videologue_web/lib
cp -R videologue/lib/videologue_web.ex videologue_umbrella/apps/videologue_web/lib
cp -R videologue/test/videologue_web videologue_umbrella/apps/videologue_web/test
cp -R videologue/test/support/conn_case.ex videologue_umbrella/apps/videologue_web/test/support

  • update endpoint.ex to have :videologue_web as otp_app attrib & from under Plug.Static

  • also update otp_app under presence.ex & add Videologue.Presence under Applications's children tree & also {Phoenix.PubSub, name: Videologue.PubSub}

  • copy assets
cp -R videologue/assets/js videologue_umbrella/apps/videologue_web/assets/js
cp -R videologue/assets/css videologue_umbrella/apps/videologue_web/assets/css

check dep paths under apps/videologue_web/assets/pacakge.json to point for root umbrella

  • add config :videologue, phoenix_token_salt: .. to configs

Running Tests

mix deps.get
pushd apps/videologue_web/assets ; npm install ; popd
  • add config :pbkdf2_elixir, :rounds, 1 to test config

Wrapping Up

[Chapter-12 OTP](./chapter-12.md