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Project: diagnose a broken service path

Last updated: 1 Oct 20268 min read
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IntermediateBy AITrove Editorial

This project traces a document-download failure from a client request to a Kubernetes Pod. Work in a disposable namespace with synthetic data. The goal is a repeatable diagnosis and a safe repair, supported by captured evidence from each network and application boundary.

Construct the path

Deploy three replicas of a small API behind a Service and an HTTPS edge route. Set readiness so an unready Pod is removed from normal traffic. Give the workload a resource request, a dedicated service account, and a NetworkPolicy that permits only the intended gateway flow. Record the image digest and baseline request success. Add an external request check and an alert whose owner can take a first action. If the test environment lacks NetworkPolicy enforcement, record that limitation rather than claiming isolation.

Output
Failure exercise: document-download
1. Break a Service selector; capture ready Pod and empty endpoint evidence.
2. Restore the selector; block the gateway with a policy change.
3. Restore traffic; serve an expired test certificate at the edge.
4. For each fault, record client error, first alert, root boundary, and repair time.

Evaluate the repair

For each injected fault, start at the client symptom. Check DNS and TLS, proxy response, Service endpoints, network policy, Pod readiness, and application logs in order. Change one variable at a time. After repair, verify a user-facing operation from outside the cluster and confirm the alert resolves. Compare the fault's detection delay with the service objective. Write a short incident record naming the first useful signal and any missing signal. Clean up the namespace after preserving the diagnostic output.

Cost and verification

The exercise consumes temporary compute, a test hostname or certificate, and monitoring capacity. An edge TLS error may never reach a Pod, so a Pod-only alert will miss it. A policy manifest accepted by the API may not be enforced by the cluster plugin. A corrected Service selector can restore endpoints without fixing an unrelated readiness failure. Keep the evidence for each layer distinct to avoid a lucky repair being misreported as a complete diagnosis.

Common Mistakes

  • Do not assume a resolved hostname means the application was reached.
  • Do not treat an empty endpoint set as a DNS fault.
  • Do not claim policy isolation until a denied connection has been tested.

Connected lessons

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