> For the complete documentation index, see [llms.txt](https://atomoh.gitbook.io/kubernetes/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://atomoh.gitbook.io/kubernetes/en/quiz-collection/service-mesh/linkerd/observability.md).
# Observability Quiz
This quiz tests your understanding of Linkerd observability features.
## Quiz Questions
### 1. Which is NOT a golden metric automatically collected by Linkerd?
A. Success rate B. Request rate (RPS) C. Latency D. CPU usage
Show Answer
**Answer: D. CPU usage**
**Explanation:** Linkerd automatically collects three golden metrics: success rate, request rate (RPS), and latency (p50, p95, p99). CPU usage is a Kubernetes metric that must be collected separately.
### 2. What is NOT included in the `linkerd viz stat` command output?
A. SUCCESS (success rate) B. RPS (request rate) C. LATENCY\_P99 D. ERROR\_TYPE
Show Answer
**Answer: D. ERROR\_TYPE**
**Explanation:** `linkerd viz stat` shows MESHED, SUCCESS, RPS, LATENCY\_P50/P95/P99. Error types must be checked via `linkerd viz tap` or logs.
### 3. What is the purpose of the `linkerd viz tap` command?
A. Network packet capture B. View real-time request stream C. Change proxy configuration D. Renew certificates
Show Answer
**Answer: B. View real-time request stream**
**Explanation:** `linkerd viz tap` streams requests in real-time. It shows request method, path, status code, latency, mTLS status, and more.
### 4. What additional metrics can be obtained by defining a ServiceProfile?
A. Pod resource usage B. Per-route metrics C. Network bandwidth D. Disk I/O
Show Answer
**Answer: B. Per-route metrics**
**Explanation:** Defining a ServiceProfile enables collection of per-route (e.g., GET /api/users, POST /api/orders) success rate, request rate, and latency metrics. View with `linkerd viz routes` command.
### 5. What is the default method to access the Viz extension's Prometheus?
A. NodePort service B. LoadBalancer service C. kubectl port-forward D. Public URL
Show Answer
**Answer: C. kubectl port-forward**
**Explanation:** Viz's Prometheus is deployed as a ClusterIP service. Access via `kubectl port-forward -n linkerd-viz svc/prometheus 9090:9090`. External exposure is not recommended for security.
### 6. Which header is NOT required for distributed tracing propagation?
A. x-b3-traceid B. x-request-id C. x-linkerd-proxy D. x-b3-spanid
Show Answer
**Answer: C. x-linkerd-proxy**
**Explanation:** Headers needed for distributed tracing: x-request-id, x-b3-traceid, x-b3-spanid, x-b3-parentspanid, x-b3-sampled, b3, etc. x-linkerd-proxy doesn't exist.
### 7. What does the `linkerd viz top` command show?
A. Pods using most resources B. Most active request paths C. Top error messages D. Latest log entries
Show Answer
**Answer: B. Most active request paths**
**Explanation:** `linkerd viz top` shows the most active request paths in real-time. It displays Source, Destination, Method, Path, Count, Latency, Success Rate, etc.
### 8. What annotation sets the proxy log level?
A. config.linkerd.io/log-level B. config.linkerd.io/proxy-log-level C. linkerd.io/proxy-log D. proxy.linkerd.io/log-level
Show Answer
**Answer: B. config.linkerd.io/proxy-log-level**
**Explanation:** The `config.linkerd.io/proxy-log-level` annotation sets the proxy log level. Example: "warn,linkerd=info,linkerd\_proxy=debug"
### 9. What is the correct Prometheus query to calculate Linkerd success rate?
A. `sum(response_total{classification="success"}) / sum(response_total)` B. `rate(success_total[5m]) / rate(request_total[5m])` C. `sum(rate(response_total{classification="success"}[5m])) / sum(rate(response_total[5m]))` D. `avg(success_rate)`
Show Answer
**Answer: C. `sum(rate(response_total{classification="success"}[5m])) / sum(rate(response_total[5m]))`**
**Explanation:** Success rate is calculated by dividing successful response rate by total response rate. The rate() function calculates per-second rate within the time range, and sum() aggregates.
### 10. What is the main function of the Jaeger extension?
A. Metrics collection B. Log aggregation C. Distributed tracing D. Traffic splitting
Show Answer
**Answer: C. Distributed tracing**
**Explanation:** The Jaeger extension provides distributed tracing. It visualizes the complete path of requests through multiple services and analyzes latency at each step.
### 11. Which view is NOT provided by the linkerd viz dashboard command?
A. Topology B. Deployments C. Pod Logs D. Routes
Show Answer
**Answer: C. Pod Logs**
**Explanation:** The Viz dashboard provides Namespace, Deployments, Pods, TCP, Routes, Topology, and Tap views. Pod logs must be checked via kubectl logs or a separate logging system.
### 12. What Viz installation option is used when integrating with external Grafana?
A. `--set grafana.external=true` B. `--set grafana.enabled=false` C. `--set grafana.url=external` D. `--set monitoring=external`
Show Answer
**Answer: B. `--set grafana.enabled=false`**
**Explanation:** When using external Grafana, disable Viz's built-in Grafana. Use `helm install linkerd-viz linkerd/linkerd-viz --set grafana.enabled=false` or configure in values file.