cytopia/metrics-server-prom repository overview

https://github.com/cytopia/metrics-server-prom⁠

⁠Overview

⁠What

A Docker image on which Prometheus⁠ can scrape Kubernetes metrics provided by metrics-server⁠. The image can run anywhere where Prometheus can use it as a target, even in Kubernetes itself.

⁠Why

metrics-server seems to be the successor of heapster⁠ for Kubernetes monitoring. However, metrics-server currently only provides its metrics in JSON format via the Kubernetes API server.

Prometheus on the other hand expects text-based format using EBNF syntax⁠ ^[1].

⁠How

The following diagram illustrates how the format transformation is achieved:

1. Prometheus scrapes the Docker container on :9100/metrics
2. Inside the Docker container uwsgi⁠ is proxying the request to kube proxy⁠
3. kube-proxy reads the provided config file and tunnels the request into Kubernetes to metrics-server
4. metrics-server replies with JSON formatted metrics
5. kube proxy forwards the request back to uwsgi
6. uwsgi calls transform.py⁠
7. transform.py rewrites the JSON into Prometheus readable output and hands the result back to uwsgi
8. uwsgi sends the final response back to Prometheus

⁠Usage

⁠Run metrics-server-prom

Simply run the Docker image with a kube config mounted into /etc/kube/config.

$ docker run -d \
    -p 9100:9100 \
    -v ${HOME}/.kube/config:/etc/kube/config:ro \
    cytopia/metrics-server-prom

If your kube config contains multiple contexts, you can tell metrics-server-prom what context to use, to connect to the cluster.

$ docker run -d \
    -p 9100:9100 \
    -v ${HOME}/.kube/config:/etc/kube/config:ro \
    -e KUBE_CONTEXT=my-context \
    cytopia/metrics-server-prom

⁠Configure Prometheus

prometheus.yml:

---
scrape_configs:
  - job_name: 'kubernetes'
    scrape_interval: '15s'
    metrics_path: '/metrics'
    static_configs:
      - targets:
        - <DOCKER_IP_ADDRESS>:9100