A short proof-of-concept tutorial of tracing using Grafana Tempo.
Tracing is a method of tracking application requests as they are processed by the application software. When a software is instrumented it produces traces, traces are made of spans hierarchically organised to form a trace. Spans are defined by a start and end time, eventually a parent span, and a number of properties that define the span characteristics (client spans, server spans, etc…).
Tracing is not limited to a single application, as the tracing context can be transmitted on the wire it is possible to collect spans from multiple applications and reconcile them in a single trace.
In the context of Kyverno, requests are usually sent by the Kubernetes API server to the Kyverno service during the admission phase. Kyverno receives and processes admission requests according to the configured policies. Every step in the admission pipeline and during the engine policy processing will produce spans. All clients (Kubernetes client, registry client and cosign client) have also been instrumented to produce client spans and transmit the tracing context on the wire.
Below is a trace for a validating admission request.
Installation and Setup
When you install Kyverno via Helm, you need to set a couple of values to enable tracing.
1$ values.yaml 2 3# ... 4 5# Enable tracing in the admission controller 6admissionController: 7 tracing: 8 # -- Enable tracing 9 enabled: true 10 # -- Traces receiver address 11 address: <backend url> 12 # -- Traces receiver port 13 port: 4317 14 15# ... 16 17# Enable tracing in the background controller 18backgroundController: 19 tracing: 20 # -- Enable tracing 21 enabled: true 22 # -- Traces receiver address 23 address: <backend url> 24 # -- Traces receiver port 25 port: 4317 26 27# ... 28 29# Enable tracing in the cleanup controller 30cleanupController: 31 tracing: 32 # -- Enable tracing 33 enabled: true 34 # -- Traces receiver address 35 address: <backend url> 36 # -- Traces receiver port 37 port: 4317 38 39# ... 40 41# Enable tracing in the reports controller 42reportsController: 43 tracing: 44 # -- Enable tracing 45 enabled: true 46 # -- Traces receiver address 47 address: <backend url> 48 # -- Traces receiver port 49 port: 4317 50 51# ...
Tracing is disabled by default and depending on the backend the associated cost can be significant.
Currently, Kyverno tracing is configured to sample all incoming requests, there’s no way to configure the tracing sampler directly in Kyverno. OpenTelemetry Collector can be used to take better sampling decision at the cost of a more advanced setup.
Additional docs and tutorials
A short proof-of-concept tutorial of tracing using Jaeger.