GitLab/Gitlab Runner

GitLab Runner is an application that works with GitLab CI/CD to run jobs in a pipeline. For more information see the official GitLab Runner documentation.

Current Gitlab Runner setup (T287504)

We're currently relying on WMCS VPSs for shared runner capacity. There is a project named gitlab-runners in which to provision new instances, and a profile to help provision Docker based runners on those instances. Note that a standalone puppetmaster in the same project stores the runner registration token under /etc/puppet/secret, and Puppet autosigning is turned off to protect the token value.

Setting up a new shared runner

To set up a new shared runner, following these steps.

1. Create a new WMCS VPS instance.
   1. Log in to [1] and navigate to the gitlab-runners project.
   2. Launch a new Debian buster instance, following the runner-{nnnn} naming convention.
   3. Add profile::gitlab::runner to the instance's Puppet Classes under the Puppet Configuration tab.
2. Wait until the new instance has fully provisioned and you can successfully ssh to the running instance using your authorized key. (This typically takes a few minutes.)
3. Do the little SSL dance that is required of instances that use a standalone puppetmaster.
   1. On the new runner (runner-{nnnn}.gitlab-runners.eqiad1.wikimedia.cloud).
      1. Run sudo rm -rf /var/lib/puppet/ssl to remove the existing SSL certs used by the default puppetmaster.
      2. Run sudo -i puppet agent --test --verbose to have the puppet client generate a new SSL cert.
   2. On gitlab-runners-puppetmaster-01.gitlab-runners.eqiad1.wikimedia.cloud sign the new instance's SSL cert.
      1. Run sudo -i puppet cert list and find the new instance in the list.
      2. Run sudo -i puppet cert sign runner-{nnnn}.gitlab-runners.eqiad1.wikimedia.cloud to sign the client cert.
4. Run sudo -i puppet agent --test --verbose on the runner to ensure it has fully provisioned the profile::gitlab::runner profile.
5. Verify that the runner has successfully registered with our GitLab instance by viewing the runner list.

Future Gitlab Runner setup (T286958)

This section contains the requirements and plan for a future Gitlab-Runner setup. The goal is to find a secure, scalable and easy to build and maintain setup for the GitLab Runner infrastructure. GitLab Runner support various environments, such as Kubernetes, Docker, OpenShift or just Linux VMs. Furthermore a wide range of compute platforms can be leveraged, such as WMCS, Ganetti, bare metal hosts or public clouds. So this section tries to compare the different options and collect advantages and disadvantages. Privacy considerations can be found in the next section.

GitLab Runner environments

GitLab Runner can be installed:

• in Linux (using official packages)
• in container
• in Kubernetes (as helm chart or agent)
• in OpenShift
• in various other environments

The follow table tries to compare the most important GitLab Runner environments available:

Environment	Advantages	Disadvantages	Additional considerations
Linux	Easy to setup low maintenance Similar to current solution	Low elasticity, difficult to scale
Container	Easy to setup low maintenance	difficult to scale auto scaling needsdocker-machine
Kubernetes	High elasticity/auto scaling	Additional Kubernetes needed (for security) Additional cluster needs maintenance More difficult to setup	Could be used to strengthen Kubernetes knowledge Auto scaling needs elastic compute plattform Maybe a general purpose non-production cluster can be build?
OpenShift		not in use in WMF

Compute Plattforms

Plattform	Advantages	Disadvantages	Additional considerations
WMCS
Ganetti
Bare metal
Public Cloud (e.g. GCP)

Elastic demand

https://docs.gitlab.com/runner/enterprise_guide/#autoscaling-configuration-one-or-more-runner-managers-multiple-workers

https://docs.gitlab.com/runner/executors/kubernetes.html

https://docs.gitlab.com/runner/configuration/autoscale.html

Monitoring of performance and usage

Gitlab-Runner export Prometheus metrics. This metrics should give insights in performance and usage. See Monitoring Gitlab Runner documentation.

However the Gitlab Runner exporter does not support authorization or https. So depending on where the Runners are hosted, a https proxy with authorization is required.