Add support for OpenStack Prometheus exporter

[matofeder]

As a CSP I want to observe my OpenStack-based IaaS infrastructure and gather relevant metrics from it. I want to use an existing Prometheus-based observability solution as storage for OpenStack metrics and then I want to see dashboards in the Grafana.

Two approaches could be used for gathering metrics from OpenStack:

• Fetch them from the OpenStack API, relevant API-based exporter https://github.com/openstack-exporter/openstack-exporter
• Fetch them from the OpenStack database, relevant DB-based exporter: https://github.com/vexxhost/openstack_database_exporter

The DB-based exporter is a very young project that is only able to gather a few metrics compared to the API-based OpenStack exporter. See the gap between the amount of metrics/sources: https://github.com/vexxhost/openstack_database_exporter/tree/main/collector and https://github.com/openstack-exporter/openstack-exporter/tree/main/exporters

An initial idea is to utilize both exporters and disable openstack_exporter metrics that can be fetched from the openstack_database_exporter. Later we could migrate some metrics sources from openstack_exporter to openstack_database_exporter, when the openstack_database_exporter grows and supports more Openstack services/metrics.

Related to: SovereignCloudStack/issues#576

[matofeder]

• Upstream API-based exporter helm chart has been updated within the following PRs:
  • Publish charts - prometheus-openstack-exporter-0.4.3 openstack-exporter/helm-charts#18
  • Add installation from helm repo into README openstack-exporter/helm-charts#19
  • Bump prometheus-openstack-exporter chart and app versions openstack-exporter/helm-charts#20

The above should ensure that the upstream helm chart installs the latest version of prometheus-openstack-exporter and the installation could be done from the GitHub helm registry.

[matofeder]

• SCS release of API-based exporter helm chart:

  • The latest released version of API-based exporter helm chart is 4 years old.
  • Therefore we released the latest chart version 0.4.3 in the SCS registry, see Publish charts - prometheus-openstack-exporter-0.4.3 openstack-exporter/helm-charts#18 (comment)

• Call to get the current state of API-based exporter helm chart

  • Is this project still active? openstack-exporter/helm-charts#21

[matofeder]

The upstream API-based exporter helm chart has been forked: scs/openstack-exporter-helm-charts as well as open PRs have been moved and merged to the new fork: #2, #3, #4

• The main motivation is PR Add extra volumes openstack-exporter-helm-charts#3. It is needed for passing the custom CA certificate into the exporter POD, see the upstream PR and the explanation there: Allow adding extra volumes to openstack-exporter deployment openstack-exporter/helm-charts#11