This one took me a while to even scope properly.
Start by clarifying requirements and constraints, then design a simple but extensible message bus with a queue and dispatch loop. Implement the bus, integrate it into a distributed workflow simulation, and write tests covering correctness, concurrency, and deduplication. Explain trade-offs and potential improvements.
Pro tip: Emphasize the importance of asynchronous delivery and how you ensure thread safety and ordering without sacrificing performance. Mention that you would use a bounded queue and backpressure to handle load spikes, and discuss how deduplication can be implemented with a seen set or idempotent receivers.
Ask about expected throughput, latency, ordering guarantees, and failure scenarios. Confirm whether deduplication is required and what the distributed workflow entails.
Outline the components: a thread-safe queue, a dispatcher (single thread or thread pool), and a registry of nodes with receiveMessage callbacks. Discuss how to handle concurrency and avoid race conditions.
Write code for registering nodes, enqueueing messages, and dispatching asynchronously. Use appropriate synchronization primitives (e.g., mutex, condition variable) and consider using a thread pool for scalability.
Choose a simple workflow like node counting or topology reconstruction. Implement nodes that send and receive messages to achieve the goal, demonstrating the bus in action.
Test correctness (all messages delivered), concurrency (multiple in-flight requests), and deduplication (if applicable). Discuss trade-offs between simplicity and performance, and potential improvements like using a lock-free queue or actor model.
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