This one took me a while to even get my head around.
Design a request-response protocol where the root sends a 'getTopology' request to its children, each child recursively gathers its subtree's topology and sends it back as a response. Use message IDs to correlate requests and responses, and handle concurrent arrivals by processing messages as they come, possibly using a state machine per node.
Pro tip: Emphasize the importance of unique message IDs and timeouts to handle lost messages, and discuss how to avoid deadlocks by ensuring responses are sent only after all children have responded.
Specify request and response message formats, including a type field, a unique message ID, sender/receiver IDs, and payload (e.g., topology string).
Each node, upon receiving a request, sends requests to all its children, waits for their responses, aggregates them into its own subtree topology, and sends a response to its parent.
Use message IDs to match responses to requests. Maintain a pending requests map to track outstanding child responses and process incoming messages asynchronously.
The root initiates the process, collects all child responses, constructs the full topology string, and prints it.
Address timeouts, retries, duplicate messages, and potential optimizations like caching or pipelining.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.