PubSubx is a simple publish-subscribe (PubSub) system built on top of Elixir's GenServer and Registry.

The module allows processes to subscribe to topics, publish messages to those topics, and manage subscriptions. It efficiently handles message delivery to subscribed processes and automatically cleans up subscriptions when processes terminate.

Features

• Subscribe/Unsubscribe: Processes can subscribe or unsubscribe from topics.
• Publish: Messages can be published to a topic, and all subscribers to that topic will receive the message.
• Dynamic Topics: Topics are dynamically created as they are subscribed to, and they are removed when no subscribers exist.
• Process Monitoring: Automatically removes subscribers when the process is no longer alive.

Auto Module

The PubSubx.Auto module is a utility that helps developers reduce boilerplate code when defining PubSubx modules.

Example Usage with the Auto Module

Define a PubSubx module:

defmodule MyApp.MyPubSub do
  use PubSubx.Auto, name: MyApp.MyPubSub
end

Include it in your supervisor tree

defmodule MyApp.Application do
  use Application

  def start(_type, _args) do
    children = [
      # Start the PubSubx server
      {MyApp.MyPubSub, []}
    ]

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

Now you can use the MyPubSub module:

# If you didn't include it in the supervisor tree, you can start it as follows:
{:ok, _pid} = MyApp.MyPubSub.start_link()

# Subscribe a pid (e.g., self()) to a topic
MyApp.MyPubSub.subscribe(:my_topic, self())

# List subscribers
subscribers = MyApp.MyPubSub.subscribers(:my_topic)

# List topics
topics = MyApp.MyPubSub.topics()

# Publish a message
MyApp.MyPubSub.publish(:my_topic, "Hello, world!")

# Unsubscribe a process from a topic
# This is optional. This happens automatically if the subscribed process dies.
MyApp.MyPubSub.unsubscribe(:my_topic, self())

Distributed Publish

You can broadcast messages in all interconnected nodes with PubSubx.distribute_publish/4 (e.g., when using libcluster).

 MyApp.MyPubSub.distribute_publish(:my_topic, "Hello, world!")

Example Usage

Start the PubSubx server:

{:ok, pid} = PubSubx.start_link(name: :my_pubsub)

Subscribe a process to a topic:

# You can use the pid or the process name
PubSubx.subscribe(:my_pubsub, :my_topic, self())
PubSubx.subscribe(pid, :other_topic, self())

Publish a message to the topic:

PubSubx.publish(:my_pubsub, :my_topic, "Hello, subscribers!")

Get the list of subscribers:

subscribers = PubSubx.subscribers(:my_pubsub, :my_topic)

Unsubscribe a process from a topic:

PubSubx.unsubscribe(:my_pubsub, :my_topic, self())