phoenix-liveview

Phoenix + LiveView (Elixir/BEAM)

Phoenix builds on Elixir and the BEAM VM to deliver fault-tolerant, real-time web applications with minimal JavaScript. LiveView keeps UI state on the server while streaming HTML diffs over WebSockets. The BEAM provides lightweight processes, supervision trees, hot code upgrades, and soft-realtime scheduling.

Key ideas

• OTP supervision keeps web, data, and background processes isolated and restartable.
• Contexts encode domain boundaries (e.g., Accounts, Billing) around Ecto schemas and queries.
• LiveView renders HTML on the server, syncing UI state over WebSockets with minimal client code.
• PubSub + Presence enable fan-out updates, tracking, and collaboration features.

---

Environment and Project Setup

# Erlang + Elixir via asdf (recommended)
asdf install erlang 27.0
asdf install elixir 1.17.3
asdf global erlang 27.0 elixir 1.17.3

# Install Phoenix generator
mix archive.install hex phx_new

# Create project with LiveView + Ecto + esbuild
mix phx.new my_app --live
cd my_app
mix deps.get
mix ecto.create
mix phx.server

Project layout (key pieces):

• lib/my_app/application.ex — OTP supervision tree (Repo, Endpoint, Telemetry, PubSub, Oban, etc.)
• lib/my_app_web/endpoint.ex — Endpoint, plugs, sockets, LiveView config
• lib/my_app_web/router.ex — Pipelines, scopes, routes, LiveSessions
• lib/my_app/ — Contexts (domain modules) and Ecto schemas
• test/support/{conn_case,data_case}.ex — Testing helpers for Ecto + Phoenix

---

BEAM + OTP Essentials

Supervision tree (application.ex): keep short, isolated children.

def start(_type, _args) do
  children = [
    MyApp.Repo,
    {Phoenix.PubSub, name: MyApp.PubSub},
    MyAppWeb.Endpoint,
    {Oban, Application.fetch_env!(:my_app, Oban)},
    MyApp.Metrics
  ]

  Supervisor.start_link(children, strategy: :one_for_one, name: MyApp.Supervisor)
end

GenServer pattern: wrap stateful services.

defmodule MyApp.Counter do
  use GenServer

  def start_link(initial \\ 0), do: GenServer.start_link(__MODULE__, initial, name: __MODULE__)
  def increment(), do: GenServer.call(__MODULE__, :inc)

  @impl true
  def handle_call(:inc, _from, state) do
    new_state = state + 1
    {:reply, new_state, new_state}
  end
end