A short overview of Umbrella Apps

Erik Nilsen

@enilsen16

What I am going to Talk About

• Microservices and my thoughts
• Talk about how other languages can be used for a similar approach
• Umbrella Apps and look at a few examples

Microservices

• Lightweight
• Combined together serve a larger goal
• Allows multiple languages to work together

Great!... Oh...

• 1500+ Microservices in prod
• Created a bad culture...
• Unsure what they do
• Things like logging became extremely difficult
• Teams had to rely on others documentation

Well what are the other options?

• Monoliths
  • Facebook takes a similar approach
• Break apps into multiple pieces but run on a central server
  • Django
  • Rails

Umbrella Apps

• Run tests in multiple apps
• Run the entire app as one or each piece individually
• Logically split up multiple apps, but keep them under one git repo

Elixir Guides Reference

Examples

Acme Bank

├── .gitignore
├── .iex.exs
├── .travis.yml
├── LICENSE.md
├── Procfile
├── README.md
├── _build
│   └── dev
├── app.json
├── apps
│   ├── auth
│   ├── backoffice
│   ├── bank
│   ├── bank_web
│   ├── master_proxy
│   ├── messenger
│   └── money
├── compile
├── config
│   └── config.exs
├── docs
│   ├── diagram.png
│   └── main.md
├── elixir_buildpack.config
├── mix.exs
├── mix.lock
├── phoenix_static_buildpack.config
└── script
    └── diagram.exs

• Two Web Apps
  • Bank Web
  • Backoffice
• Logic Specific Apps
  • Money
  • Messenger
  • Bank
• Deployment App
  • Master Proxy

Approach

Phoenix 1.3 Umbrella

• Wanted a similar approach
• Going to multiple web applications
• Break entire DB into its own app
• Needed to work either together or individually
• Also needed to work on heroku

What we wanted

Nifty

• Master proxy also calls multiple web apps
• Avoids circular dependencies

├── .gitignore
├── .travis.yml
├── Procfile
├── README.md
├── _build
│   ├── dev
│   └── test
├── apps
│   ├── agent_web
│   ├── auth
│   ├── company_web
│   ├── hook
│   ├── master_proxy
│   └── nifty_db
├── compile
├── config
│   └── config.exs
├── elixir_buildpack.config
├── erl_crash.dump
├── mix.exs
├── mix.lock
└── phoenix_static_buildpack.config

Avoid starting an app multiple times

  def start(_type, _args) do
    import Supervisor.Spec

    # Define workers and child supervisors to be supervised
    children = [
      # Start the endpoint when the application starts
      supervisor(AgentWeb.Web.Endpoint, []),
      # Start your own worker by calling: AgentWeb.Worker.start_link(arg1, arg2, arg3)
      # worker(AgentWeb.Worker, [arg1, arg2, arg3]),
    ]

    repo = if :erlang.whereis(NiftyDB.Repo) == :undefined, do: [supervisor(NiftyDB.Repo, [])], else: []
    # See http://elixir-lang.org/docs/stable/elixir/Supervisor.html
    # for other strategies and supported options
    opts = [strategy: :one_for_one, name: AgentWeb.Supervisor]
    Supervisor.start_link(children ++ repo ++ guardian_db, opts)
  end

Exploration Ideas

• Try an umbrella app where BEAM starts multiple apps from different languages
  • Python
  • Ruby
  • Rust?

Umbrella Apps Don't Solve all Your Problems

You still need to architect correctly :)

Questions?