[Best Practice Proposal]: liveness probes for CNFs

[taylor]

Summary

A cloud native principle is that application developers understand their own resilience requirements better than operators[1]. This is exemplified in the Kubernetes best practice of pods declaring how they should be managed through the liveness and readiness entries in the pod's configuration.

Motivation

liveness probes are part of the onboarding and the ongoing health checks for CNFs.

Goals

No response

Non-Goals

No response

Proposal

No response

Workload Context

No response

User Stories

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Notes, Caveats, Constraints

No response

References

liveness probes are part of the onboarding and the ongoing health checks for CNFs.

• See #243 for readiness probe issue
• Dependence on other CNFs or microservices before responding to readiness / liveness tests
• Readiness vs liveliness probes: How to set them up and when to use them in your Kubernetes cluster | Google Cloud Blog
• Configure Liveness, Readiness and Startup Probes | Kubernetes
• Rationale from cnf-testsuite: https://github.com/cncf/cnf-testsuite/blob/main/RATIONALE.md#to-test-if-there-is-a-liveness-entry-in-the-helm-chart-liveness
• • https://kubernetes.io/docs/tasks/configure-pod-container/configure-liveness-readiness-startup-probes/
• [1] "No one knows more about what an application needs to run in a healthy state than the developer. For a long time, infrastructure administrators have tried to figure out what “healthy” means for applications they are responsible for running. Without knowledge of what actually makes an application healthy, their attempts to monitor and alert when applications are unhealthy are often fragile and incomplete. To increase the operability of cloud native applications, applications should expose a health check."" Garrison, Justin; Nova, Kris. Cloud Native Infrastructure: Patterns for Scalable Infrastructure and Applications in a Dynamic Environment . O'Reilly Media. Kindle Edition.

[taylor]

Draft started here https://docs.google.com/document/d/1WW_k8IUrwoVijmTIQLOyEj5a-5Y0OG5YnbCA4i-HU9Q/edit

[taylor]

This has lots of content to pull from already as well as a draft to continue