SlackBot WS – an OTP-first Socket Mode framework for Slack bots

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Reconnects. Backoff. Heartbeats. Slack’s per-method rate limit. Traffic shaping. SlackBot WS handles all of it—and makes building a bot feel like the reason you picked Elixir. This is not a thin API wrapper; it’s an OTP-first Socket Mode runtime.

For slash commands, you declare your command grammar—no regexes or nested conditionals. SlackBot compiles it into a parser at build time.

defmodule MyApp.SlackBot do
  use SlackBot, otp_app: :my_app

  # /deploy api        → %{service: "api"}
  # /deploy api canary → %{service: "api", canary?: true}
  slash "/deploy" do
    grammar do
      value :service
      optional literal("canary", as: :canary?)
    end

    handle payload, _ctx do
      Deployments.kick(payload["parsed"].service)
    end
  end
end

Slash commands aren’t the only thing routed this way. Event handlers work the same:

handle_event "app_mention", event, _ctx do
  SlackBot.push(MyApp.SlackBot, {"chat.postMessage", %{
    channel: event["channel"],
    text: "Hi <@#{event["user"]}>!"
  }})
end

SlackBot WS handles the tier limits and throttling for you.

And middleware works the way you’d expect if you’re familiar with Plug—just over Slack events instead of HTTP.

defmodule MyApp.LogMiddleware do
  def call(_type, payload, ctx) do
    Logger.debug("Slack event: #{payload["type"]}")
    {:cont, payload, ctx}
  end
end

middleware MyApp.LogMiddleware

Return {:cont, payload, ctx} to continue, {:halt, response} to short-circuit.

That’s it. Add your API tokens, supervise the module, ship.

The defaults are production-ready. ETS for cache and event buffer. Sensible backoff. Rate limiting on. You can swap cache adapters if you want to go multi-node, tune timeouts, wire up Telemetry dashboards—but you don’t have to touch any of it until you need to.

SlackBot WS is an extraction of something else I’m building, and I want to share it with those who just want to write Slack bots without the Slack complexity—be they one-off utilities or large bots. Maybe that’s you.

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2

This is great! But it’s a shame that Slack doesn’t allow Socket Mode in the public Slack Marketplace, so it’s only usable for internal tools.

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Thanks, Ostap. It really is a shame. I can envision a handful of historical reasons why that is (not built on the BEAM being one :slight_smile:). That said, this is an extraction of a more sophisticated HTTP-event driven framework I’m building, and may release some version of it.

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