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Intro and configuration

Prometheus adapter is a kubernetes addon that permits to expose custom metrics to the kubernetes metrics API. For that, prometheus adapter asks to a prometheus intance in order to build the desired metrics.

It can be used to serve the resource metrics api, this is cpu and memory from pods and nodes. It can be used, for example, for autoescaling purposes using Horizontal Pod Autoescaler, replacing metrics-server.

  • Resource metrics api

For example, to access the resource metrics api we can

kubectl get --raw "/apis/metrics.k8s.io/v1beta1/nodes"
kubectl get --raw "/apis/metrics.k8s.io/v1beta1/pods"
  • Custom metrics api
  • External metrics

The parameters

The prometheus instance is passed with the parameter --prometheus-url. For example:

--prometheus-url=

--prometheus-url=https://prometheus.monitoring.svc:9090/

The configuration file of the prometeus adapter is passed with the parameter --config. For example:

--config=/etc/adapter/config.yaml

The configuration file

The config.yaml file has some section:

resourceRules:  for resource metrics
rules:    for custom metrics
externalRules:   for external metrics

Every rule has 4 parts.

  • Discovery
  • Association
  • Naming
  • Querying
  • Prometheus adapter github

https://github.com/kubernetes-sigs/prometheus-adapter/

  • Prometheus adapter helm chart

https://github.com/prometheus-community/helm-charts/tree/main/charts/prometheus-adapter

https://github.com/kubernetes-sigs/prometheus-adapter/blob/master/docs/config.md https://github.com/kubernetes-sigs/prometheus-adapter/blob/master/docs/config-walkthrough.md https://github.com/kubernetes-sigs/prometheus-adapter/blob/master/docs/walkthrough.md https://github.com/kubernetes-sigs/prometheus-adapter/blob/master/docs/sample-config.yaml https://github.com/kubernetes-sigs/prometheus-adapter/blob/master/docs/externalmetrics.md