k3s/contrib/prometheus

Prometheus in Kubernetes

This is an experimental Prometheus setup for monitoring Kubernetes services that expose prometheus-friendly metrics through address http://service_address:service_port/metrics.

Purpose

The purpose of the setup is to gather performance-related metrics during load tests and analyze them to find and fix bottlenecks.

Quick start

Promdash/Prometheus

1. Pick a local directory for promdash. It can be any directory, preferably one which is stable and which you don't mind keeping around. Then (in our case, we use /mnt/promdash, just run this docker command docker run -v /mnt/promdash:/mnt/promdash -e DATABASE_URL=sqlite3:/mnt/promdash/file.sqlite3 prom/promdash ./bin/rake db:migrate. In the future, we might use mysql as the promdash database, however, in any case, this 1 time db setup step is required.

Now quickly confirm that /mnt/promdash/file.sqlite3 exists, and has a non-zero size, and make sure its permissions are open so that containers can read from it. For example:

    [jay@rhbd kubernetes]$ ls -altrh /mnt/promdash/
    total 20K
    drwxr-xr-x. 6 root root 4.0K May  6 23:12 ..
    -rwxrwxrwx  1 root root  12K May  6 23:33 file.sqlite3

Looks open enough :).

1. Now, you can start this pod, like so kubectl create -f cluster/add-ons/prometheus/prometheusB3.yaml. This pod will start both prometheus, the server, as well as promdash, the visualization tool. You can then configure promdash, and next time you restart the pod - you're configuration will be remain (since the promdash directory was mounted as a local docker volume).

2. Finally, you can simply access localhost:3000, which will have promdash running. Then, add the prometheus server (locahost:9090)to as a promdash server, and create a dashboard according to the promdash directions.

Prometheus

You can launch prometheus easily, by simply running.

kubectl create -f cluster/addons/prometheus/prometheus.yaml

This will bind to port 9090 locally. You can see the prometheus database at that URL.

How it works

This is a v1beta1 based, containerized prometheus pod, which scrapes endpoints which are readable on the KUBERNETES_RO service (the internal kubernetes service running in the default namespace, which is visible to all pods).

1. The KUBERNETES_RO service is already running : providing read access to the API metrics.

2. The list of services to be monitored is passed as a command line aguments in the yaml file.

3. The startup scripts assumes that each service T will have 2 environment variables set T_SERVICE_HOST and T_SERVICE_PORT

4. Each can be configured manually in yaml file if you want to monitor something that is not a regular Kubernetes service. For example, you can add comma delimted endpoints which can be scraped like so...

- -t
- KUBERNETES_RO,MY_OTHER_METRIC_SERVICE

Other notes

For regular Kubernetes services the env variables are set up automatically and injected at runtime.

By default the metrics are written to a temporary location (that can be changed in the the volumes section of the yaml file). Prometheus' UI is available at port 9090.

TODO

• We should publish this image into the kube/ namespace.
• Possibly use postgre or mysql as a promdash database.
• push gateway (https://github.com/prometheus/pushgateway) setup.
• Setup high availability via NFS