Adds support for attaching GCEPersitentDisks

Adds GCEPersistentDisk volume struct
Adds gce-utils to attach disk to kubelet's VM.
Updates config to give compute-rw to every minion.
Adds GCEPersistentDisk to API
Adds ability to mount attached disks
Generalizes PD and adds tests.
PD now uses an pluggable API interface.
Unit Tests more cleanly separates TearDown and SetUp
Modify boilerplate hook to omit build tags
Adds Mounter interface; mount is now built by OS
TearDown() for PD now detaches disk on final refcount
Un-generalized PD; GCE calls moved to cloudprovider

Address comments.

pkg/cloudprovider/gce/gce.go

@@ -23,6 +23,7 @@ import (
 	"net"
 	"net/http"
 	"os/exec"
+	"path"
 	"strconv"
 	"strings"
 	"time"
@@ -41,43 +42,71 @@ type GCECloud struct {
 	service    *compute.Service
 	projectID  string
 	zone       string
-	instanceRE string
+	instanceID string
 }
 
 func init() {
 	cloudprovider.RegisterCloudProvider("gce", func(config io.Reader) (cloudprovider.Interface, error) { return newGCECloud() })
 }
 
-func getProjectAndZone() (string, string, error) {
+func getMetadata(url string) (string, error) {
 	client := http.Client{}
-	url := "http://metadata/computeMetadata/v1/instance/zone"
 	req, err := http.NewRequest("GET", url, nil)
 	if err != nil {
-		return "", "", err
+		return "", err
 	}
 	req.Header.Add("X-Google-Metadata-Request", "True")
 	res, err := client.Do(req)
 	if err != nil {
-		return "", "", err
+		return "", err
 	}
 	defer res.Body.Close()
 	data, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		return "", err
+	}
+	return string(data), nil
+}
+
+func getProjectAndZone() (string, string, error) {
+	url := "http://metadata/computeMetadata/v1/instance/zone"
+	result, err := getMetadata(url)
 	if err != nil {
 		return "", "", err
 	}
-	parts := strings.Split(string(data), "/")
+	parts := strings.Split(result, "/")
 	if len(parts) != 4 {
-		return "", "", fmt.Errorf("Unexpected response: %s", string(data))
+		return "", "", fmt.Errorf("Unexpected response: %s", result)
 	}
 	return parts[1], parts[3], nil
 }
 
+func getInstanceID() (string, error) {
+	url := "http://metadata/computeMetadata/v1/instance/hostname"
+	result, err := getMetadata(url)
+	if err != nil {
+		return "", err
+	}
+	parts := strings.Split(result, ".")
+	if len(parts) == 0 {
+		return "", fmt.Errorf("Unexpected response: %s", result)
+	}
+	return parts[0], nil
+}
+
 // newGCECloud creates a new instance of GCECloud.
 func newGCECloud() (*GCECloud, error) {
 	projectID, zone, err := getProjectAndZone()
 	if err != nil {
 		return nil, err
 	}
+	// TODO: if we want to use this on a machine that doesn't have the http://metadata server
+	// e.g. on a user's machine (not VM) somewhere, we need to have an alternative for
+	// instance id lookup.
+	instanceID, err := getInstanceID()
+	if err != nil {
+		return nil, err
+	}
 	client, err := serviceaccount.NewClient(&serviceaccount.Options{})
 	if err != nil {
 		return nil, err
@@ -87,9 +116,10 @@ func newGCECloud() (*GCECloud, error) {
 		return nil, err
 	}
 	return &GCECloud{
-		service:   svc,
-		projectID: projectID,
-		zone:      zone,
+		service:    svc,
+		projectID:  projectID,
+		zone:       zone,
+		instanceID: instanceID,
 	}, nil
 }
 
@@ -310,6 +340,29 @@ func (gce *GCECloud) GetZone() (cloudprovider.Zone, error) {
 	}, nil
 }
 
+func (gce *GCECloud) AttachDisk(diskName string, readOnly bool) error {
+	disk, err := gce.getDisk(diskName)
+	if err != nil {
+		return err
+	}
+	readWrite := "READ_WRITE"
+	if readOnly {
+		readWrite = "READ_ONLY"
+	}
+	attachedDisk := gce.convertDiskToAttachedDisk(disk, readWrite)
+	_, err = gce.service.Instances.AttachDisk(gce.projectID, gce.zone, gce.instanceID, attachedDisk).Do()
+	return err
+}
+
+func (gce *GCECloud) DetachDisk(devicePath string) error {
+	_, err := gce.service.Instances.DetachDisk(gce.projectID, gce.zone, gce.instanceID, devicePath).Do()
+	return err
+}
+
+func (gce *GCECloud) getDisk(diskName string) (*compute.Disk, error) {
+	return gce.service.Disks.Get(gce.projectID, gce.zone, diskName).Do()
+}
+
 // getGceRegion returns region of the gce zone. Zone names
 // are of the form: ${region-name}-${ix}.
 // For example "us-central1-b" has a region of "us-central1".
@@ -321,3 +374,14 @@ func getGceRegion(zone string) (string, error) {
 	}
 	return zone[:ix], nil
 }
+
+// Converts a Disk resource to an AttachedDisk resource.
+func (gce *GCECloud) convertDiskToAttachedDisk(disk *compute.Disk, readWrite string) *compute.AttachedDisk {
+	return &compute.AttachedDisk{
+		DeviceName: disk.Name,
+		Kind:       disk.Kind,
+		Mode:       readWrite,
+		Source:     "https://" + path.Join("www.googleapis.com/compute/v1/projects/", gce.projectID, "zones", gce.zone, "disks", disk.Name),
+		Type:       "PERSISTENT",
+	}
+}