parse kubelet checkpoint file for pod devices

Enabling kubelete checkpoint file  parsing to get Pod device info
so that these device information can be passed into CNI plugins
that need specific device information to work on.

Change-Id: I6630f56adc0a8307f575fc09ce9090c1ffca0337

checkpoint/checkpoint.go

@@ -0,0 +1,76 @@
+package checkpoint
+
+import (
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+
+	"github.com/intel/multus-cni/types"
+)
+
+const (
+	checkPointfile = "/var/lib/kubelet/device-plugins/kubelet_internal_checkpoint"
+)
+
+type PodDevicesEntry struct {
+	PodUID        string
+	ContainerName string
+	ResourceName  string
+	DeviceIDs     []string
+	AllocResp     []byte
+}
+
+type checkpointData struct {
+	PodDeviceEntries  []PodDevicesEntry
+	RegisteredDevices map[string][]string
+}
+
+type Data struct {
+	Data     checkpointData
+	Checksum uint64
+}
+
+// getPodEntries gets all Pod device allocation entries from checkpoint file
+func getPodEntries() ([]PodDevicesEntry, error) {
+
+	podEntries := []PodDevicesEntry{}
+
+	cpd := &Data{}
+	rawBytes, err := ioutil.ReadFile(checkPointfile)
+	if err != nil {
+		return podEntries, fmt.Errorf("getPodEntries(): error reading file %s\n%v\n", checkPointfile, err)
+
+	}
+
+	if err = json.Unmarshal(rawBytes, cpd); err != nil {
+		return podEntries, fmt.Errorf("getPodEntries(): error unmarshalling raw bytes %v", err)
+	}
+
+	return cpd.Data.PodDeviceEntries, nil
+}
+
+// GetComputeDeviceMap returns a map of resourceName to list of device IDs
+func GetComputeDeviceMap(podID string) (map[string]*types.ResourceInfo, error) {
+
+	resourceMap := make(map[string]*types.ResourceInfo)
+	podEntires, err := getPodEntries()
+
+	if err != nil {
+		return nil, err
+	}
+
+	for _, pod := range podEntires {
+		if pod.PodUID == podID {
+			entry, ok := resourceMap[pod.ResourceName]
+			if ok {
+				// already exists; append to it
+				entry.DeviceIDs = append(entry.DeviceIDs, pod.DeviceIDs...)
+			} else {
+				// new entry
+				resourceMap[pod.ResourceName] = &types.ResourceInfo{DeviceIDs: pod.DeviceIDs}
+			}
+		}
+	}
+
+	return resourceMap, nil
+}