Only some of the Downward API information is available through envvars and downwardAPI volumes

[metral]

On k8s v1.11 we have access to information that is available to containers through environment variables and/or downward API volumes.

However, in using either envvars or downwardAPI volumes, not all of this information is available. I can't tell if it's something on our end, and if so where.

In our nodejs output types, comments aside, we actually only support the following info for each implementation:

• Env vars using valueFrom.fieldRef:

  • spec.nodeName - the node’s name
  • status.hostIP - the node’s IP
  • metadata.name - the pod’s name
  • metadata.namespace - the pod’s namespace
  • status.podIP - the pod’s IP address
  • spec.serviceAccountName - the pod’s service account name
  • metadata.uid - the pod’s UID
  • metadata.labels[''] - the value of the pod’s label (for example, metadata.labels['mylabel'])
  • metadata.annotations[''] - the value of the pod’s annotation (for example, metadata.annotations['myannotation'])

• DownwardAPI volumes via items of fieldRef:

  • spec.nodeName - the node’s name
  • status.hostIP - the node’s IP
  • metadata.name - the pod’s name
  • metadata.namespace - the pod’s namespace
  • status.podIP - the pod’s IP address
  • spec.serviceAccountName - the pod’s service account name
  • metadata.uid - the pod’s UID
  • metadata.labels- the value of the pod’s label (for example, metadata.labels['mylabel'])
  • metadata.annotations - the value of the pod’s annotation (for example, metadata.annotations['myannotation'])

Attempts to access any of the missing info from either implementation method, returns an error similar to the following: e.g when using envvars we can't accessmetadata.labels or metadata.annotations:

error: Plan apply failed: Job.batch "cts-auto-metral-job-datadirector-kx9bp16g" is invalid:

[spec.template.spec.containers[0].env[6].valueFrom.fieldRef.fieldPath: Unsupported value: "metadata.labels": supported values: "metadata.name", "metadata.namespace", "metadata.uid", "spec.nodeName", "spec.serviceAccountName", "status.hostIP", "status.podIP",

spec.template.spec.containers[0].env[7].valueFrom.fieldRef.fieldPath: Unsupported value: "metadata.annotations": supported values: "metadata.name", "metadata.namespace", "metadata.uid", "spec.nodeName", "spec.serviceAccountName", "status.hostIP", "status.podIP", 

spec.template.spec.initContainers[0].env[4].valueFrom.fieldRef.fieldPath: Unsupported value: "metadata.labels": supported values: "metadata.name", "metadata.namespace", "metadata.uid", "spec.nodeName", "spec.serviceAccountName", "status.hostIP", "status.podIP", 

spec.template.spec.initContainers[0].env[5].valueFrom.fieldRef.fieldPath: Unsupported value: "metadata.annotations": supported values: "metadata.name", "metadata.namespace", "metadata.uid", "spec.nodeName", "spec.serviceAccountName", "status.hostIP", "status.podIP"]

It's worth noting, that:

• for envvars we are missing metadata.labels and metadata.annotations, which are both lists/arrays of values, whereas we do support envvars values that are single values e.g. spec.podIP.
• for downwardAPI volumes we can only access the Pod's metadata object, but not its spec or status

/cc @lblackstone @hausdorff

[hausdorff]

This seems like it would have to be enforced by the API server -- we definitely don't mess with this information directly. The v1.13 docs say the same thing, though. Are we sure this isn't a bug in upstream?

[lblackstone]

Given that the problem only seems to be present on list items, I wonder if this is another incarnation of the bug I fixed in #461

[metral]

The list problem only applies to the envvars, but not to the downwardAPI volumes, as those map to files in the container which do hold the list items. However, oddly enough the downwardAPI does not do this to any other value, list or singular, other the for the metadata

[lblackstone]

Unable to repro on this old issue, so closing it out.