Sprint 9 - Minimal observability¶

Objective. Add structured logging and lifecycle tracing for industrial debugging.

Deliverable. Lifecycle behavior is debuggable without print statements.

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Decisions already made¶

Observability stays lightweight and rclpy-native.
Lifecycle diagnostics should be available through structured logs before any external metrics or tracing integration is considered.
Detailed hook and gating information belongs at debug level; transition summaries may use a higher level if they remain useful.

Standardize lifecycle logs for:

Optionally measure hook duration and include it in debug-level logs.

Candidate read-only surfaces:

Exact field names for structured log messages.
Whether last-error and transition-history surfaces are part of this sprint or stay behind logging only.
The size and ordering of any bounded transition history.

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[ ] Transition logs include target state and component count.
[ ] Hook logs include component name, hook name, result, and duration when enabled.
[ ] Gating logs include action and allowed/denied outcome.
[ ] Last error is captured and cleared according to the contract.
[ ] Transition history, if added, is bounded and deterministic.

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Risk: noisy logs. Keep detailed messages at debug level and reserve info for transition summaries.

Risk: observability becomes a dependency magnet. Keep the core rclpy-only; external metrics/tracing adapters stay application code.

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In scope:

Out of scope:

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