loopsocial / eredis_sub

Elixir wrapper for eredis pub/sub functionality

THIS PACKAGE IS UNMAINTAINED, AND RETIRED FROM HEX.PM

EredisSub

Wraps eredis and eredis_sub functionallity for Elixir usage.

• Publishes binary messages to Redis Pub/Sub channels.
• Subscribes to channels and calls a handler function when a message is received.

Usage

Publish

EredisSub.publish("my_channel", "Hello, world!")

Subscribe

Implement the behaviour to be called when a message is received:

defmodule MyModule do
  @behaviour EredisSub.Handler

  @impl EredisSub.Handler
  def handle_pubsub_message(message, metadata) do
    # Do something...
  end
end

Subscribe to a channel:

metadata_example = %{subscribed_at: DateTime.utc_now()}
EredisSub.subscribe("my_channel", MyModule, metadata_example)

Installation

def deps do
  [
    {:eredis_sub, "~> 0.1.0"}
  ]
end

Add the following to your supervision tree on application.ex:

children = [
  EredisSub
]

Optional configuration can be passed to eredis and eredis_sub, check their docs:

children = [
  {EredisSub, [database: 2, username: "foo", password: "bar"]}
]

Motivations

Why not use Phoenix.PubSub?

Because multiple applications in many programming languages can use Redis Pub/Sub, but they don't serialize their binary messages according to Phoenix schema.

Why not use eredis directly?

That's also a great option. With EredisSub Elixir abstraction we intend to hide Erlang specific knowledge, for example Erlang strings and OTP processes. We changed the API to let clients subscribe a handler function to a Pub/Sub channel, similar to how :telemetry attaches handlers.

We sacrificed flexibility on client process architecture, for a simpler mental model. If you need to handle message passing or a pool of processes, for example to handle heavier loads, use eredis directly.

Why not use Redix?

Because it doesn't support Redis Cluster. Since our project already depends on eredis_cluster (thus also depends on eredis), we wanted to stick with it.