Support Monitoring container vitality

[schaefi]

Problem description

A “healthcheck” is a way in which a user can determine the “health” or readiness of the primary process running inside of a container. It is more than a simple “is my container running?” question. Think of it more like “is my application ready?” So, a healthcheck is really a way to verify that both the container and its applications are responsive.

For details see:

• https://developers.redhat.com/blog/2019/04/18/monitoring-container-vitality-and-availability-with-podman

Expected behaviour

kiwi should be able to make use of the healtcheck feature

[schaefi]

Note: Healthchecks are supported by buildah but not by umoci as of this time

[davidcassany]

As noted in opencontainers/umoci#352 (comment) when I asked for healthcheck support umoci maintainers noted me this is not an standard OCI feature, this is docker specific. So this brings up some considerations:

• KIWI containers are all OCI images at build time only on the very last step they are converted from OCI to Docker format
• Do we want to support non OCI features?
• umoci can't be used to set the healthcheck as it implements the OCI standard
• Buildah ignores healthcheck flags if they are used on non Docker images, which is the case in KIWI

So keeping the current implementation of container builds in KIWI it is not straight forward to include healthcheck support, as KIWI by design builds OCI images.

There could be a chance to implement support for it limited to buildah but this would require a relevant refactor. It is not clear to me the effort is worth.

[schaefi]

I'm closing this one for now as I don't think we will address this in the near future for the reasons written down