Collecting Metrics in Knative

Knative supports different popular tools for collecting metrics:

• Prometheus
• OpenTelemetry Collector

Grafana dashboards are available for metrics collected directly with Prometheus.

You can also set up the OpenTelemetry Collector to receive metrics from Knative components and distribute them to other metrics providers that support OpenTelemetry.

Warning

You can't use OpenTelemetry Collector and Prometheus at the same time. The default metrics backend is Prometheus. You will need to remove metrics.backend-destination and metrics.request-metrics-backend-destination keys from the config-observability Configmap to enable Prometheus metrics.

About Prometheus

Prometheus is an open-source tool for collecting, aggregating timeseries metrics and alerting. It can also be used to scrape the OpenTelemetry Collector that is demonstrated below when Prometheus is used.

Setting up Prometheus

1. Install the Prometheus Operator by using Helm:

   helm repo add prometheus-community https://prometheus-community.github.io/helm-charts
   helm repo update
   helm install prometheus prometheus-community/kube-prometheus-stack -n default -f values.yaml
   # values.yaml contains at minimum the configuration below
   

   Caution

   You will need to ensure that the helm chart has following values configured, otherwise the ServiceMonitors/Podmonitors will not work.

   kube-state-metrics:
     metricLabelsAllowlist:
       - pods=[*]
       - deployments=[app.kubernetes.io/name,app.kubernetes.io/component,app.kubernetes.io/instance]
   prometheus:
     prometheusSpec:
       serviceMonitorSelectorNilUsesHelmValues: false
       podMonitorSelectorNilUsesHelmValues: false
   

2. Apply the ServiceMonitors/PodMonitors to collect metrics from Knative.

   kubectl apply -f https://raw.githubusercontent.com/knative-extensions/monitoring/main/servicemonitor.yaml
   

3. Grafana dashboards can be imported from the knative-extensions repository.

4. If you are using the Grafana Helm Chart with the Dashboard Sidecar enabled, you can load the dashboards by applying the following configmaps.

   kubectl apply -f https://raw.githubusercontent.com/knative-extensions/monitoring/main/grafana/dashboards.yaml
   

Access the Prometheus instance locally

By default, the Prometheus instance is only exposed on a private service named prometheus-operated.

To access the console in your web browser:

1. Enter the command:

   kubectl port-forward -n default svc/prometheus-operated 9090
   

2. Access the console in your browser via http://localhost:9090.

About OpenTelemetry

OpenTelemetry is a CNCF observability framework for cloud-native software, which provides a collection of tools, APIs, and SDKs.

You can use OpenTelemetry to instrument, generate, collect, and export telemetry data. This data includes metrics, logs, and traces, that you can analyze to understand the performance and behavior of Knative components.

OpenTelemetry allows you to easily export metrics to multiple monitoring services without needing to rebuild or reconfigure the Knative binaries.

Understanding the collector

The collector provides a location where various Knative components can push metrics to be retained and collected by a monitoring service.

In the following example, you can configure a single collector instance using a ConfigMap and a Deployment.

Tip

For more complex deployments, you can automate some of these steps by using the OpenTelemetry Operator.

Caution

The Grafana dashboards at https://github.com/knative-extensions/monitoring/tree/main/grafana don't work with metrics scraped from OpenTelemetry Collector.

Set up the collector

1. Create a namespace for the collector to run in, by entering the following command:

   kubectl create namespace metrics
   

   The next step uses the metrics namespace for creating the collector.

2. Create a Deployment, Service, and ConfigMap for the collector by entering the following command:

   kubectl apply -f https://raw.githubusercontent.com/knative/docs/main/docs/serving/observability/metrics/collector.yaml
   

3. Update the config-observability ConfigMaps in the Knative Serving and Eventing namespaces, by entering the follow command:

   kubectl patch --namespace knative-serving configmap/config-observability \
     --type merge \
     --patch '{"data":{"metrics.backend-destination":"opencensus","metrics.request-metrics-backend-destination":"opencensus","metrics.opencensus-address":"otel-collector.metrics:55678"}}'
   kubectl patch --namespace knative-eventing configmap/config-observability \
     --type merge \
     --patch '{"data":{"metrics.backend-destination":"opencensus","metrics.opencensus-address":"otel-collector.metrics:55678"}}'
   

Verify the collector setup

1. You can check that metrics are being forwarded by loading the Prometheus export port on the collector, by entering the following command:

   kubectl port-forward --namespace metrics deployment/otel-collector 8889
   

2. Fetch http://localhost:8889/metrics to see the exported metrics.