nodes-containers-downward-api-container-resources-envars.adoc

Consuming container resources using environment variables

When creating pods, you can use the downward API to inject information about computing resource requests and limits using environment variables.

Procedure

To use environment variables:

1. When creating a pod configuration, specify environment variables that correspond to the contents of the resources field in the spec.container field:

   ....
   spec:
     containers:
       - name: test-container
         image: gcr.io/google_containers/busybox:1.24
         command: [ "/bin/sh", "-c", "env" ]
         resources:
           requests:
             memory: "32Mi"
             cpu: "125m"
           limits:
             memory: "64Mi"
             cpu: "250m"
         env:
           - name: MY_CPU_REQUEST
             valueFrom:
               resourceFieldRef:
                 resource: requests.cpu
           - name: MY_CPU_LIMIT
             valueFrom:
               resourceFieldRef:
                 resource: limits.cpu
           - name: MY_MEM_REQUEST
             valueFrom:
               resourceFieldRef:
                 resource: requests.memory
           - name: MY_MEM_LIMIT
             valueFrom:
               resourceFieldRef:
                 resource: limits.memory
   ....

   If the resource limits are not included in the container configuration, the downward API defaults to the node’s CPU and memory allocatable values.

2. Create the pod from the pod.yaml file:

   $ oc create -f pod.yaml