Overview
Module: ARR Data Model & Compose
Activity type: Lesson (Orient → Recall → Learn → Explain → Reflect)
Learning objective: Explain why a running process is not necessarily a healthy or ready service
Bloom level: Understand / Apply
Last reviewed: 2025-02-20
Learning objective
Explain why a running process is not necessarily a healthy or ready service
Why this matters
Teach operators to distinguish process state from service health, model startup and runtime dependencies, and apply bounded restart behavior without creating restart loops or hiding real failures.
Learn
Complete the module reading first:
Feynman teach-back: required
prompt
Explain the lesson to a new operator using a restaurant analogy.
model_explanation
A process is like a restaurant building with the lights on. Liveness asks whether staff are present and able to respond. Readiness asks whether the kitchen can actually serve customers now. A food delivery service is a dependency: opening the restaurant after the delivery truck arrives does not guarantee ingredients were unloaded and checked. A restart policy is like sending the manager home and bringing in a replacement when the manager fails. That may help after a temporary problem, but repeatedly replacing managers will not fix an empty pantry. Traffic should be paused when the restaurant is unready, while restarts should be reserved for failures that a fresh process can plausibly correct.
self_check
If your explanation treats process existence, readiness, and liveness as the same condition, revise it until each signal has a distinct meaning and response.
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Reflection
- What did I learn?
- What did I struggle with?
- How does this connect to earlier classes?