Phoenix.PubSub Documentation

To initialize Phoenix.PubSub, add it as a child to your application's supervision tree. You must provide a unique name for the PubSub instance.

defmodule MyApp do
  use Application

  def start(_type, _args) do
    children = [
      {Phoenix.PubSub, name: MyApp.PubSub}
    ]

    opts = [strategy: :one_for_one, name: MyApp.Supervisor]
    Supervisor.start_link(children, opts)
  end
end

To use Phoenix.PubSub in your project, add it to your mix.exs dependencies list.

def deps do
  [{:phoenix_pubsub, "~> 2.0"}]
end

Phoenix.PubSub tests spawn nodes internally to simulate a distributed environment. If you want to run tests that do not require clustering, use the --exclude clustered flag with mix test.

$ mix test --exclude clustered

If you encounter issues running clustered tests, ensure the Erlang Port Mapper Daemon (epmd) is running by executing the following command before running your tests:

$ epmd -daemon

Once your PubSub instance is running, you can use Phoenix.PubSub.subscribe/2 to listen to a specific topic and Phoenix.PubSub.broadcast/3 to send messages to that topic.

# Subscribe to a topic
Phoenix.PubSub.subscribe(MyApp.PubSub, "user:123")

# Broadcast a message to a topic
Phoenix.PubSub.broadcast(MyApp.PubSub, "user:123", :hello_world)