You've built a checkout reactor that reserves inventory, charges a card, generates a shipping label, and sends a confirmation email. It runs through Sidekiq. When something fails, compensation logic rolls it back. It works.
Then your team asks: "How many checkouts failed this week? Which step? How long does the charge step take at p99? Can we see a trace through the entire system?"
Before v0.5.0, you'd need to add logging calls to every step, build a custom Sidekiq middleware, and figure out how to correlate traces across async job boundaries. Now it's one line of config.
Enter Middlewares
Ruby Reactor 0.5.0 introduces a middleware pipeline — the same pattern that powers Rack, but designed for saga execution. A middleware is a plain Ruby object that hooks into the reactor lifecycle:
