The
topic commands use iceoryx2 service discovery, so they work from any
directory, no workspace required. Run them in a second terminal while a graph
is running.List and inspect live topics
cerulion topic list enumerates active topics, sorted by name.
No active topics.
cerulion topic info <topic> prints details for a single topic:
Watch messages with echo
cerulion topic echo <topic> subscribes and prints each message until you press Ctrl+C.
std_msgs/String and sensor_msgs/Image messages (identified by their schema hash). For any other schema, it prints a hex preview of the payload.
Measure publish rate
cerulion topic hz <topic> measures how often a topic publishes, until Ctrl+C.
For the periodic camera created with
--policy period_ms=33, topic hz
should report roughly 30 Hz.Open the interactive dashboard
cerulion tui launches an interactive terminal dashboard. Logging is suppressed while the TUI is open.
Inspect recorded traces
cerulion trace inspect <dir> reads trace_*.jsonl bag files from a directory (in lexicographic order) and prints one line per record:
| Flag | Value | Effect |
|---|---|---|
-t / --filter | TOPIC | Show only records for this exact topic. |
-n / --limit | N | Print at most N records. |
-r / --reverse | None | Reverse order (most recent first). |
Tracing is built into the runtime: every graph run automatically produces
trace_*.jsonl bag files via the publish trace, so there’s nothing extra to
start or configure. cerulion trace inspect reads those bags afterward.Clean up stale services
iceoryx2 keeps on-disk bookkeeping for each node. When a graph’s topology changes between runs, stale entries from dead nodes can cause discovery errors.cerulion clean removes bookkeeping for dead nodes only; live sibling processes are left untouched. It prints cleanup counts and per-cause remediation.
Next steps
Wire and run a graph
Produce the topics you inspect here.
Messages and schemas
Understand the message shapes that echo prints.