Mesh Observability Language
5 exercises — 5 exercises practising service mesh observability vocabulary — golden signals, Kiali service graphs, distributed tracing, and Envoy metrics language.
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A team says: "One benefit of the service mesh is that we get L7 observability without application code changes." What does this mean?
Envoy operates at L7 (application layer) — it understands HTTP, gRPC, and headers — so it can generate rich metrics for every request without the application doing anything.
Compare this to L3/L4 monitoring (IP/port level — e.g., network flow logs): at L4, you can see "X bytes from service A to service B," but you can't see HTTP status codes or request paths. Envoy sees everything at L7: the HTTP method, URL path, response code, and response time for every request. It exposes these as Prometheus metrics (istio_requests_total, istio_request_duration_milliseconds) with labels for source service, destination service, and response code — enabling per-route latency and error dashboards with zero application instrumentation.
Key vocabulary:
• L7 observability — metrics at the HTTP/gRPC application layer (status codes, latency, routes)
• istio_requests_total — Prometheus counter: request count per source/destination/status_code
• zero instrumentation — mesh-generated metrics require no application code changes
Compare this to L3/L4 monitoring (IP/port level — e.g., network flow logs): at L4, you can see "X bytes from service A to service B," but you can't see HTTP status codes or request paths. Envoy sees everything at L7: the HTTP method, URL path, response code, and response time for every request. It exposes these as Prometheus metrics (istio_requests_total, istio_request_duration_milliseconds) with labels for source service, destination service, and response code — enabling per-route latency and error dashboards with zero application instrumentation.
Key vocabulary:
• L7 observability — metrics at the HTTP/gRPC application layer (status codes, latency, routes)
• istio_requests_total — Prometheus counter: request count per source/destination/status_code
• zero instrumentation — mesh-generated metrics require no application code changes