Cantido / solvent

An event bus for Elixir

Solvent

An event bus built for ease-of-use.

Installation

If available in Hex, the package can be installed by adding solvent to your list of dependencies in mix.exs:

def deps do
  [
    {:solvent, "~> 0.3.0"}
  ]
end

Documentation can be generated with ExDoc and published on HexDocs. Once published, the docs can be found at https://hexdocs.pm/solvent.

Usage

Solvent is flexible enough to offer several ways of delivering events, and is exensible enough to add your own. Out of the box, Solvent allows you to subscribe with anonymous functions, module-function-args tuples, PIDs, and modules that use the Solvent.Subscriber module.

# anonymous functions
Solvent.subscribe(
  fn event_id, _subscriber_id -> IO.inspect(event_id) end,
  source: "https://myapp.example.com",
  types: ["com.myevent.published"]
)

# module-function-args tuples
Solvent.subscribe(
  {IO, :inspect, []},
  source: "https://myapp.example.com",
  types: ["com.myevent.published"]
)

# PIDs
Solvent.subscribe(
  self(),
  source: "https://myapp.example.com",
  types: ["com.myevent.published"]
)

# Subscriber modules
defmodule MySubscriber do
  use Solvent.Subscriber,
    source: "https://myapp.example.com",
    types: ["com.myevent.published"]

  @impl true
  def handle_event(_event_id) do
    IO.puts("I'm handling an event!")
  end
end

Set up your subscriptions in your application's start/2 function.

def start(_type, _args) do
  Solvent.subscribe(MySubscriber)

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

Finally, publish your event using Solvent.publish/2.

Solvent.publish("com.myevent.published")

Specify additonal event data with the :data option. You can specify any optional field from the CloudEvent spec, in fact.

Solvent.publish(
  "com.myjsonevent.published",
  source: "https://myapp.example.com",
  datacontenttype: "application/json",
  data: ~s({"foo":"bar"})
)

Only event IDs are passed to subscriber functions. You must fetch the associated event using Solvent.EventStore.fetch/1. This small hiccup in an otherwise buttery-smooth developer experience is done in the name of speed. Copying large amounts of data between processes can be slow, so Solvent stores events in an ETS table and lets you fetch them when you're ready.

Clustering

Currently, Solvent only communicates on the local node. I do plan on building a cluster-aware bus, or an AMQP adapter, or something like that.

License

MIT License

Copyright 2022 Rosa Richter

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.