Support activeDeadlineSeconds for pods spawned by kubernetes executor

Description

Problem / Use Case

In a multi-tenant deployment of Kubernetes, some form of resource quota enforcement must be implemented to prevent service abuse. OpenShift implements multiple quota scopes utilizing a Pod resource's activeDeadlineSeconds property. Having separate quotas (Terminating for ephemeral pods and NotTerminating for longer-lived pods) helps to improve utilization density and reduce over-provisioning of compute resources.

The kubernetes executor in GitLab Runner allows GitLab CI jobs to run inside Kubernetes pods ephemerally. However, these pods are not recognized as short-lived by Kubernetes/OpenShift and thus do not benefit from all of the platforms' built-in features. For end-users reaching the limits of their resource quotas, this results in failed GitLab CI jobs .

Goals

• Support OpenShift Quota Scopes (Terminating, NotTerminating, etc)
• Leverage Kubernetes built-in pod lifecycle management

Benefits

• Users of the Kubernetes executor of GitLab Runner in a multi-tenant OpenShift environment will have less failed jobs from exceeding quota
• Reduced job runtime as a result of faster pod scheduling - potentially (OpenShift)
• Reduced resource contention with long-lived pods (OpenShift)
• Simplified and more robust pod lifecycle management (Kubernetes)

Proposal

Extend the kubernetes executor of GitLab Runner to add support for activeDeadlineSeconds.

• the value for activeDeadlineSeconds will be set based on the timeout setting of the job, project, and runner.

• the feature will be put behind a feature flag (disabled by default)

• By leveraging an existing Gitlab CI setting, no additional configuration is needed by the end-user.

• On the backend, all associated pods that are spawned by the kubernetes executor have activeDeadlineSeconds set, allowing Kubernetes to automatically manage their lifecycle. Additionally, on multi-tenant OpenShift deployments with enforced quotas, the presence of activeDeadlineSeconds setting results in pods having the Terminating Quota Scope (instead of NotTerminating).

Links to related issues and merge requests / references

• #3259
• https://docs.openshift.com/container-platform/4.11/applications/quotas/quotas-setting-per-project.html#quotas-scopes_quotas-setting-per-project
• https://docs.openshift.com/container-platform/4.11/nodes/jobs/nodes-nodes-jobs.html#jobs-set-max_nodes-nodes-jobs
• https://kubernetes.io/docs/concepts/workloads/controllers/job/#job-termination-and-cleanup
• https://kubernetes.io/docs/reference/kubernetes-api/workload-resources/pod-v1/#lifecycle
• https://docs.gitlab.com/ee/ci/yaml/#timeout
• https://docs.gitlab.com/ee/ci/pipelines/settings.html#set-a-limit-for-how-long-jobs-can-run
• https://docs.gitlab.com/ee/ci/runners/configure_runners.html#set-maximum-job-timeout-for-a-runner

~"type::feature".