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📜 WAYPOINT LESSON

Checkpoint — The Thread-Safe Job Queue

⭐⭐ intermediate⏳ 25 min read📍 Lesson 119 of 265

Combine locking, atomic updates, and worker coordination into a queue that never loses or duplicates work.

The gate (mini-build)

A job queue drained by concurrent workers — the producer/consumer core:

  1. Enqueue(string job) → adds a job.
  2. RunAll(int workers) → starts workers threads; each worker repeatedly takes one job (if any) and processes it: call CjConcurrency.Pause() (the simulated work), then record "done:" + job into the results.
  3. Every job is processed EXACTLY ONCE — no losses, no duplicates — even though workers take jobs one at a time from a shared queue.
  4. Results exposes the recorded entries; RunAll returns after all workers finish (join your threads).

The graded test runs 20 jobs across 4 workers with 5 ms simulated work and asserts exact counts and no duplicates.