Note_Tech

All technological notes.

---

Project maintained by simonangel-fong Hosted on GitHub Pages — Theme by mattgraham

Kubernetes: Storage - Downward API

Back

• Kubernetes: Storage - Downward API
  • Downward API
    • Common feilds

---

Downward API

• Downward API

  • a Kubernetes mechanism that allows a container to consume information about itself or its host without using the Kubernetes client or API server.
  • a way to inject values from the pod’s metadata, spec, or status fields down into the container.

• 2 types of injection:

  • as env ver
    • pod’s general metadata: spec.containers.env.fieldRef
    • resource constraints: spec.containers.env.resourceFieldRef
  • as file: spec.volumes.downwardAPI

---

Common feilds

• Available from fieldRef field

fieldRef Fields	env	vol	DESC
metadata.name	Y	Y	pod’s name.
metadata.namespace	Y	Y	pod’s namespace.
metadata.uid	Y	Y	pod’s uid.
metadata.labels	N	Y	pod’s labels.
metadata.labels['key']	Y	Y	value of the specified label.
metadata.annotations	N	Y	pod’s annotations.
metadata.annotations['key']	Y	Y	The value of the specified annotation.
spec.nodeName	Y	N	name of the worker node the pod runs on.
spec.serviceAccountName	Y	N	name of the pod’s service account.
status.podIP	Y	N	pod’s IP address.
status.hostIP	Y	N	worker node’s IP address.

• Available from resourceFieldRef field

resourceFieldRef Fields	env	vol	DESC
requests.cpu	Y	Y	container’s CPU request.
requests.memory	Y	Y	container’s memory request.
requests.ephemeral-storage	Y	Y	container’s ephemeral storage request.
limits.cpu	Y	Y	container’s CPU limit.
limits.memory	Y	Y	container’s memory limit.
limits.ephemeral-storage	Y	Y	container’s ephemeral storage limit.

• For resource fields, the containerName field must be specified because volumes are defined at the pod level and it isn’t obvious which container’s resources are being referenced.

---