Evaluate Startup Probes For Product Profile Deployments

[chirangaalwis]

Description:
As per a suggestion by @lakwarus, it was identified that we need to evaluate the Kubernetes startup probe feature.

Affected Product Version:
Helm Resources for WSO2 API Management version 3.1.0.3 and above

[chirangaalwis]

As per the initial evaluation, the following were noted.

• This feature provides a better solution for tracking the startup progress, avoiding the need to provide a value which could be too low or high as a grace period (currently, handled via intialDelaySeconds of the Kubernetes liveness probe.
• One concern is that this feature is available from Kubernetes API version 1.16 onwards, which may hinder users who use Kubernetes clusters of versions lower than that.

Please find this article which provides a better understanding of this feature, its pros and cons.

[chirangaalwis]

As per further discussion, it was suggested to hold integrating this feature to WSO2 product Helm resources since, it was observed that the stable and default Kubernetes API server version among many of the Kubernetes managed services provided by major cloud providers as of now, is version 1.14.

Example, see AWS EKS and GKE.

Kubernetes API server version 1.16 is already supported by many of the cloud vendors though it is not the default. Thus, we expect to introduce this feature in a future resource release.

Please feel free to share your thoughts and concerns with regards to this matter.

[chirangaalwis]

Moving to https://github.com/wso2/kubernetes-apim/milestone/24 as patterns 1 and 2 are yet to be addressed.