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Blunt Toolkit

There is currently only one "tool" in this repo. The Aggregate Inspector.

threequarterspi over on Slack asked if anyone had implemented some sort of time-traveling for Commanded.

I immediately thought of the redux devtools and thought that would be pretty cool for viewing aggregate state over time...with real data.

So I set out to get a bit of something working.

After discovering and digging a bit into ratatouille, I was able to get that little something.

aggregate_inspector.mp4

Usage

Add {:blunt_toolkit, github: "elixir-blunt/blunt_toolkit", runtime: false, only: :dev} to your deps and run mix deps.get.

You can launch the UI with mix blunt.inspect.aggregate.

That can be a drag to type all the time, so I would recommend assigning an alias in your mix file.

  def aliases do
    [
      view_state: "blunt.inspect.aggregate"
    ]
  end

and make sure you're including aliases in your project function.

  def project do
    [
      ...
      deps: deps(),
      aliases: aliases(),
      ...
    ]
  end

Now you can just run mix view_state

Navigation

You can use the ⬆ / ⬇ or j / k keys to navigate through the history of your aggregate.

Exiting

Strike Ctrl+c with some heft.

notes

  • The event store module you enter must be a valid EventStore.

  • The aggregate module you enter must be a valid aggregate module with an apply/2 function.

  • The stream must exist. Duh

  • The next time you run the mix task, it will present you with your last answers as defaults.

Development

You'll need a local postgres install with username postgres and password postgres (or alter config/config.exs)

To populate some events run mix test

Then start the UI via mix view_state.

Debugging this is difficult to say the least. Logs are swallowed, and it seems all IO functions are swallowed as well.

I just start a file in init, define a log function, and simply call log when I need to see something.

  def init(_context) do
    {:ok, file} = File.open("debug.log", [:append, {:delayed_write, 100, 20}]
        config = %{
          logfile: file,
      stream: "",
      ...
  end

  defp log(%{logfile: logfile}, title \\ "", content) do
    IO.binwrite(
      logfile,
      title <> " - " <> inspect(content, pretty: true, limit: :infinity) <> "\n"
    )

    content
  end

Things to consider.

This was a result of about 2 hours of playing around. It's not optimized for large streams.

It would be nice to be able to just grab n events up front and request more events as needed.

But ¯\_(ツ)_/¯