# Guided Exercise: Applying the Framework to a Broken Service, on Paper First

Before the `endpoint-fix-task` Lab, walk through the framework yourself against a described
symptom — no cluster needed yet.

## The scenario

A teammate says: "`my-svc` isn't routing any traffic to our Pods, and I don't know why — the
Pods look healthy in `kubectl get pods`."

## Your task

Write out, step by step, what you would actually DO for each framework stage, before looking at
the worked answer:

1. **Observe** — what's the precise, specific symptom here (not "it's broken")?
2. **Gather Evidence** — name the exact `kubectl` commands you'd run, in order, and what each
   one is checking for.
3. **Form Hypothesis** — based on what ROOT 07's Services lesson taught you, what's the most
   likely cause of "Pods healthy, but Service routes nowhere"?
4. **Test** — how would you CONFIRM that hypothesis before changing anything?
5. **Repair** — what's the minimal fix, assuming your hypothesis is correct?
6. **Validate** — what would you check afterward to PROVE the fix worked, not just assume it?

## A worked answer to check yourself against

1. Traffic sent to `my-svc` never reaches any Pod, despite the Pods themselves reporting
   `Running`/`Ready` — this rules out "the Pods are unhealthy" as the cause.
2. `kubectl get endpoints my-svc` (does it show any Pod IPs at all?), then `kubectl describe
   service my-svc` (what selector is it actually using?), then `kubectl get pods --show-labels`
   (what labels do the real Pods actually carry?).
3. A Service-to-Pod label selector mismatch — exactly the failure mode ROOT 07's demonstration
   walked through, where a Service's selector no longer matches the Pods' actual labels.
4. Directly compare the Service's selector (from `describe service`) against the Pods' labels
   (from `get pods --show-labels`) side by side — confirmed if they genuinely don't match.
5. Correct the Service's selector (or the Pods' labels, whichever is actually wrong) so they
   match again.
6. `kubectl get endpoints my-svc` now shows the Pod IPs populated — not just "the YAML looks
   right now," but the actual Endpoints object reflecting real, matched Pods.

## Instructor Notes

**Facilitation:** This exercise deliberately reuses ROOT 07's own content — a good moment to
point out explicitly that the framework's value is applying PRIOR knowledge systematically, not
learning something entirely new each time.

**Approximate timing:** 10-12 minutes live with discussion; 10 minutes self-paced.

**Optional extension:** ask what would change about steps 2-4 if the symptom were instead
"Pods healthy, but ONE specific caller can't reach the Service while others can" — a good bridge
to considering NetworkPolicy (ROOT 09) as an alternative hypothesis once the simpler
selector-mismatch explanation is ruled out.