Guided beta caseProbeginnerQoS reliability
The topic exists but no messages arrive
Restore the obstacle pipeline while preserving the sensor driver's best-effort profile.
Pairs with QoS policies in ROS 2 Systems Debugging. Read the concept first, then diagnose it here.
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`/scan` is visible in the graph, but the reliable subscriber receives zero messages.
Ubuntu 24.04, ROS 2 Jazzy, Python and C++ nodes, browser telemetry workspace
System boundary
Trace only the relevant path.
LiDAR publisher/scanobstacle subscriber
How this lab works
You diagnose it — no command list.
Open the repair workspace and gather your own evidence in a real terminal. No diagnostic commands are handed to you — finding the fault is the exercise. Stuck? Progressive hints unlock inside the workspace.
Verification
Your repair must pass more than the visible symptom.
- Subscriber receives at least 9 Hz
- Graph retains one publisher
- Hidden regression behavior
- Root cause explanation