How to migrate from p-j-e to script exporter

Prerequisites

• A deployed cos-lite bundle in a Kubernetes environment
• Juju controller >= 3.0

Machines running Ubuntu >= 22.04. It might also be available for focal in the future.

Explanation

The charm script-exporter is a subordinate charm that allows the execution of a custom script that generates a custom prometheus metric.

The metrics that p-j-e generates are to detect the type of juju machines e.g: lxd, kvm, qemu or bare metal. The same can be done by using systemd-detect-virt in a custom script

Step-to-step

• Deploy charm grafana-agent
• Deploy charm script-exporter-operator
• Relate any principal application with grafana-agent. Note that grafana-agent should be related with just one principal on the same machine due technical limitations
• Relate grafana-agent with script-exporter
• Relate the principal with script-exporter

Configuration files

Script (systemd_virt.sh)

#!/bin/bash

if [[ $# -ne 2 ]]; then
    echo "Usage: $0 <cloud_name> <customer>"
    exit 1
fi

cloud_name=$1
customer=$2


# Run systemd-detect-virt to get the virtualization type
virt_type=$(systemd-detect-virt 2>/dev/null)
ret=$?

if [[ $ret -ne 0 || "$virt_type" == "none" ]]; then
    virt_type="metal"
fi

# Convert the output into a Prometheus metric

echo "# HELP system_virtualization_type Virtualization type detected by systemd-detect-virt"
echo "# TYPE system_virtualization_type gauge"
echo "system_virtualization_type{cloud_name=\"$cloud_name\",customer=\"$customer\",hostname=\"$(hostname)\",type=\"$virt_type\"} 1"

exit 0

Prometheus configuration (prometheus.yaml)

scrape_configs:
  - job_name: 'script_systemd_virt' # job name, arbitrary
    metrics_path: /probe
    params:
      script: [systemd_virt] # the name of the script as specified in the *config_file*
      prefix: [script] # a custom prefix for this metric
    static_configs:
      - targets:
        - 127.0.0.1

Generic configuration (script-exporter.yaml)

scripts:
  - name: systemd_virt # Name of the script, arbitrary
    command: /etc/script-exporter-script # any available shell command, or `/etc/script-exporter-script` for the custom one
    args:
      - "Foo" # cloud_name
      - "Bar" # customer

Set the charm configurations

juju config script-exporter script_file=@systemd_virt.sh
juju config script-exporter config_file=@script-exporter.yaml
juju config script-exporter prometheus_config_file=@prometheus.yaml

After that you should be able to see the metric on prometheus with the same fields that used to have on p-j-e