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/volume/gce_util.go

@@ -0,0 +1,136 @@
+/*
+Copyright 2014 Google Inc. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package volume
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"path"
+	"path/filepath"
+	"regexp"
+	"strings"
+	"time"
+
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/cloudprovider"
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/cloudprovider/gce"
+)
+
+const partitionRegex = "[a-z][a-z]*(?P<partition>[0-9][0-9]*)?"
+
+var regexMatcher = regexp.MustCompile(partitionRegex)
+
+type GCEDiskUtil struct{}
+
+// Attaches a disk specified by a volume.GCEPersistentDisk to the current kubelet.
+// Mounts the disk to it's global path.
+func (util *GCEDiskUtil) AttachDisk(GCEPD *GCEPersistentDisk) error {
+	gce, err := cloudprovider.GetCloudProvider("gce", nil)
+	if err != nil {
+		return err
+	}
+	flags := uintptr(0)
+	if GCEPD.ReadOnly {
+		flags = MOUNT_MS_RDONLY
+	}
+	if err := gce.(*gce_cloud.GCECloud).AttachDisk(GCEPD.PDName, GCEPD.ReadOnly); err != nil {
+		return err
+	}
+	devicePath := path.Join("/dev/disk/by-id/", "google-"+GCEPD.PDName)
+	if GCEPD.Partition != "" {
+		devicePath = devicePath + "-part" + GCEPD.Partition
+	}
+	//TODO(jonesdl) There should probably be better method than busy-waiting here.
+	numTries := 0
+	for {
+		_, err := os.Stat(devicePath)
+		if err == nil {
+			break
+		}
+		if err != nil && !os.IsNotExist(err) {
+			return err
+		}
+		numTries++
+		if numTries == 10 {
+			return errors.New("Could not attach disk: Timeout after 10s")
+		}
+		time.Sleep(time.Second)
+	}
+	globalPDPath := makeGlobalPDName(GCEPD.RootDir, GCEPD.PDName, GCEPD.ReadOnly)
+	// Only mount the PD globally once.
+	_, err = os.Stat(globalPDPath)
+	if os.IsNotExist(err) {
+		err = os.MkdirAll(globalPDPath, 0750)
+		if err != nil {
+			return err
+		}
+		err = GCEPD.mounter.Mount(devicePath, globalPDPath, GCEPD.FSType, flags, "")
+		if err != nil {
+			os.RemoveAll(globalPDPath)
+			return err
+		}
+	} else if err != nil {
+		return err
+	}
+	return nil
+}
+
+func getDeviceName(devicePath, canonicalDevicePath string) (string, error) {
+	isMatch := regexMatcher.MatchString(path.Base(canonicalDevicePath))
+	if !isMatch {
+		return "", fmt.Errorf("unexpected device: %s", canonicalDevicePath)
+	}
+	if isMatch {
+		result := make(map[string]string)
+		substrings := regexMatcher.FindStringSubmatch(path.Base(canonicalDevicePath))
+		for i, label := range regexMatcher.SubexpNames() {
+			result[label] = substrings[i]
+		}
+		partition := result["partition"]
+		devicePath = strings.TrimSuffix(devicePath, "-part"+partition)
+	}
+	return strings.TrimPrefix(path.Base(devicePath), "google-"), nil
+}
+
+// Unmounts the device and detaches the disk from the kubelet's host machine.
+// Expects a GCE device path symlink. Ex: /dev/disk/by-id/google-mydisk-part1
+func (util *GCEDiskUtil) DetachDisk(GCEPD *GCEPersistentDisk, devicePath string) error {
+	// Follow the symlink to the actual device path.
+	canonicalDevicePath, err := filepath.EvalSymlinks(devicePath)
+	if err != nil {
+		return err
+	}
+	deviceName, err := getDeviceName(devicePath, canonicalDevicePath)
+	if err != nil {
+		return err
+	}
+	globalPDPath := makeGlobalPDName(GCEPD.RootDir, deviceName, GCEPD.ReadOnly)
+	if err := GCEPD.mounter.Unmount(globalPDPath, 0); err != nil {
+		return err
+	}
+	if err := os.RemoveAll(globalPDPath); err != nil {
+		return err
+	}
+	gce, err := cloudprovider.GetCloudProvider("gce", nil)
+	if err != nil {
+		return err
+	}
+	if err := gce.(*gce_cloud.GCECloud).DetachDisk(deviceName); err != nil {
+		return err
+	}
+	return nil
+}