Downward API implementation for resources limits and requests

pkg/fieldpath/fieldpath.go

@@ -18,8 +18,12 @@ package fieldpath
 
 import (
 	"fmt"
+	"math"
+	"strconv"
 
+	"k8s.io/kubernetes/pkg/api"
 	"k8s.io/kubernetes/pkg/api/meta"
+	"k8s.io/kubernetes/pkg/api/resource"
 )
 
 // formatMap formats map[string]string to a string.
@@ -58,3 +62,61 @@ func ExtractFieldPathAsString(obj interface{}, fieldPath string) (string, error)
 
 	return "", fmt.Errorf("Unsupported fieldPath: %v", fieldPath)
 }
+
+// ExtractResourceValueByContainerName extracts the value of a resource
+// by providing container name
+func ExtractResourceValueByContainerName(fs *api.ResourceFieldSelector, pod *api.Pod, containerName string) (string, error) {
+	container, err := findContainerInPod(pod, containerName)
+	if err != nil {
+		return "", err
+	}
+	return ExtractContainerResourceValue(fs, container)
+}
+
+// ExtractContainerResourceValue extracts the value of a resource
+// in an already known container
+func ExtractContainerResourceValue(fs *api.ResourceFieldSelector, container *api.Container) (string, error) {
+	divisor := resource.Quantity{}
+	if divisor.Cmp(fs.Divisor) == 0 {
+		divisor = resource.MustParse("1")
+	} else {
+		divisor = fs.Divisor
+	}
+
+	switch fs.Resource {
+	case "limits.cpu":
+		return convertResourceCPUToString(container.Resources.Limits.Cpu(), divisor)
+	case "limits.memory":
+		return convertResourceMemoryToString(container.Resources.Limits.Memory(), divisor)
+	case "requests.cpu":
+		return convertResourceCPUToString(container.Resources.Requests.Cpu(), divisor)
+	case "requests.memory":
+		return convertResourceMemoryToString(container.Resources.Requests.Memory(), divisor)
+	}
+
+	return "", fmt.Errorf("Unsupported container resource : %v", fs.Resource)
+}
+
+// findContainerInPod finds a container by its name in the provided pod
+func findContainerInPod(pod *api.Pod, containerName string) (*api.Container, error) {
+	for _, container := range pod.Spec.Containers {
+		if container.Name == containerName {
+			return &container, nil
+		}
+	}
+	return nil, fmt.Errorf("container %s not found", containerName)
+}
+
+// convertResourceCPUTOString converts cpu value to the format of divisor and returns
+// ceiling of the value.
+func convertResourceCPUToString(cpu *resource.Quantity, divisor resource.Quantity) (string, error) {
+	c := int64(math.Ceil(float64(cpu.MilliValue()) / float64(divisor.MilliValue())))
+	return strconv.FormatInt(c, 10), nil
+}
+
+// convertResourceMemoryToString converts memory value to the format of divisor and returns
+// ceiling of the value.
+func convertResourceMemoryToString(memory *resource.Quantity, divisor resource.Quantity) (string, error) {
+	m := int64(math.Ceil(float64(memory.Value()) / float64(divisor.Value())))
+	return strconv.FormatInt(m, 10), nil
+}