Bull Exporter is a Prometheus metrics exporter for Bull queues running on Redis. It provides an HTTP server (default port 9538) that exposes queue state metrics (waiting, active, delayed, failed, completed counts) and job duration summaries. It supports automatic queue discovery by scanning Redis keys, and can also be run in one-shot mode to print metrics to stdout. The application is built with Express, Bull, ioredis, and prom-client, and is packaged as a Docker image. The codebase is well-structured with TypeScript, strict compiler options, comprehensive unit tests using Jest and real Redis, and CI/CD pipelines (Travis CI and CircleCI). However, the project has been stale since October 2020, uses very outdated dependencies (Node.js 10, TypeScript 3.9, old prom-client), and has no recent maintenance activity. The code quality is solid for its time but suffers from technical drift.