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rbd_util.go
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rbd_util.go
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/*
Copyright 2014 The Kubernetes Authors.
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.
*/
//
// utility functions to setup rbd volume
// mainly implement diskManager interface
//
package rbd
import (
"encoding/json"
"errors"
"fmt"
"io/ioutil"
"math/rand"
"os"
"path"
"regexp"
"strings"
"time"
"github.com/golang/glog"
"k8s.io/kubernetes/pkg/util/exec"
"k8s.io/kubernetes/pkg/util/mount"
"k8s.io/kubernetes/pkg/util/node"
"k8s.io/kubernetes/pkg/volume"
)
// search /sys/bus for rbd device that matches given pool and image
func getDevFromImageAndPool(pool, image string) (string, bool) {
// /sys/bus/rbd/devices/X/name and /sys/bus/rbd/devices/X/pool
sys_path := "/sys/bus/rbd/devices"
if dirs, err := ioutil.ReadDir(sys_path); err == nil {
for _, f := range dirs {
// pool and name format:
// see rbd_pool_show() and rbd_name_show() at
// https://github.com/torvalds/linux/blob/master/drivers/block/rbd.c
name := f.Name()
// first match pool, then match name
po := path.Join(sys_path, name, "pool")
img := path.Join(sys_path, name, "name")
exe := exec.New()
out, err := exe.Command("cat", po, img).CombinedOutput()
if err != nil {
continue
}
matched, err := regexp.MatchString("^"+pool+"\n"+image+"\n$", string(out))
if err != nil || !matched {
continue
}
// found a match, check if device exists
devicePath := "/dev/rbd" + name
if _, err := os.Lstat(devicePath); err == nil {
return devicePath, true
}
}
}
return "", false
}
// stat a path, if not exists, retry maxRetries times
func waitForPath(pool, image string, maxRetries int) (string, bool) {
for i := 0; i < maxRetries; i++ {
devicePath, found := getDevFromImageAndPool(pool, image)
if found {
return devicePath, true
}
time.Sleep(time.Second)
}
return "", false
}
// make a directory like /var/lib/kubelet/plugins/kubernetes.io/pod/rbd/pool-image-image
func makePDNameInternal(host volume.VolumeHost, pool string, image string) string {
return path.Join(host.GetPluginDir(rbdPluginName), "rbd", pool+"-image-"+image)
}
type RBDUtil struct{}
func (util *RBDUtil) MakeGlobalPDName(rbd rbd) string {
return makePDNameInternal(rbd.plugin.host, rbd.Pool, rbd.Image)
}
func (util *RBDUtil) rbdLock(b rbdMounter, lock bool) error {
var err error
var output, locker string
var cmd []byte
var secret_opt []string
if b.Secret != "" {
secret_opt = []string{"--key=" + b.Secret}
} else {
secret_opt = []string{"-k", b.Keyring}
}
// construct lock id using host name and a magic prefix
lock_id := "kubelet_lock_magic_" + node.GetHostname("")
l := len(b.Mon)
// avoid mount storm, pick a host randomly
start := rand.Int() % l
// iterate all hosts until mount succeeds.
for i := start; i < start+l; i++ {
mon := b.Mon[i%l]
// cmd "rbd lock list" serves two purposes:
// for fencing, check if lock already held for this host
// this edge case happens if host crashes in the middle of acquiring lock and mounting rbd
// for defencing, get the locker name, something like "client.1234"
cmd, err = b.plugin.execCommand("rbd",
append([]string{"lock", "list", b.Image, "--pool", b.Pool, "--id", b.Id, "-m", mon}, secret_opt...))
output = string(cmd)
if err != nil {
continue
}
if lock {
// check if lock is already held for this host by matching lock_id and rbd lock id
if strings.Contains(output, lock_id) {
// this host already holds the lock, exit
glog.V(1).Infof("rbd: lock already held for %s", lock_id)
return nil
}
// hold a lock: rbd lock add
cmd, err = b.plugin.execCommand("rbd",
append([]string{"lock", "add", b.Image, lock_id, "--pool", b.Pool, "--id", b.Id, "-m", mon}, secret_opt...))
} else {
// defencing, find locker name
ind := strings.LastIndex(output, lock_id) - 1
for i := ind; i >= 0; i-- {
if output[i] == '\n' {
locker = output[(i + 1):ind]
break
}
}
// remove a lock: rbd lock remove
cmd, err = b.plugin.execCommand("rbd",
append([]string{"lock", "remove", b.Image, lock_id, locker, "--pool", b.Pool, "--id", b.Id, "-m", mon}, secret_opt...))
}
if err == nil {
//lock is acquired
break
}
}
return err
}
func (util *RBDUtil) persistRBD(rbd rbdMounter, mnt string) error {
file := path.Join(mnt, "rbd.json")
fp, err := os.Create(file)
if err != nil {
return fmt.Errorf("rbd: create err %s/%s", file, err)
}
defer fp.Close()
encoder := json.NewEncoder(fp)
if err = encoder.Encode(rbd); err != nil {
return fmt.Errorf("rbd: encode err: %v.", err)
}
return nil
}
func (util *RBDUtil) loadRBD(mounter *rbdMounter, mnt string) error {
file := path.Join(mnt, "rbd.json")
fp, err := os.Open(file)
if err != nil {
return fmt.Errorf("rbd: open err %s/%s", file, err)
}
defer fp.Close()
decoder := json.NewDecoder(fp)
if err = decoder.Decode(mounter); err != nil {
return fmt.Errorf("rbd: decode err: %v.", err)
}
return nil
}
func (util *RBDUtil) fencing(b rbdMounter) error {
// no need to fence readOnly
if (&b).GetAttributes().ReadOnly {
return nil
}
return util.rbdLock(b, true)
}
func (util *RBDUtil) defencing(c rbdUnmounter) error {
// no need to fence readOnly
if c.ReadOnly {
return nil
}
return util.rbdLock(*c.rbdMounter, false)
}
func (util *RBDUtil) AttachDisk(b rbdMounter) error {
var err error
var output []byte
devicePath, found := waitForPath(b.Pool, b.Image, 1)
if !found {
// modprobe
_, err = b.plugin.execCommand("modprobe", []string{"rbd"})
if err != nil {
return fmt.Errorf("rbd: failed to modprobe rbd error:%v", err)
}
// rbd map
l := len(b.Mon)
// avoid mount storm, pick a host randomly
start := rand.Int() % l
// iterate all hosts until mount succeeds.
for i := start; i < start+l; i++ {
mon := b.Mon[i%l]
glog.V(1).Infof("rbd: map mon %s", mon)
if b.Secret != "" {
output, err = b.plugin.execCommand("rbd",
[]string{"map", b.Image, "--pool", b.Pool, "--id", b.Id, "-m", mon, "--key=" + b.Secret})
} else {
output, err = b.plugin.execCommand("rbd",
[]string{"map", b.Image, "--pool", b.Pool, "--id", b.Id, "-m", mon, "-k", b.Keyring})
}
if err == nil {
break
}
glog.V(1).Infof("rbd: map error %v %s", err, string(output))
}
if err != nil {
return fmt.Errorf("rbd: map failed %v %s", err, string(output))
}
devicePath, found = waitForPath(b.Pool, b.Image, 10)
if !found {
return errors.New("Could not map image: Timeout after 10s")
}
}
// mount it
globalPDPath := b.manager.MakeGlobalPDName(*b.rbd)
notMnt, err := b.mounter.IsLikelyNotMountPoint(globalPDPath)
// in the first time, the path shouldn't exist and IsLikelyNotMountPoint is expected to get NotExist
if err != nil && !os.IsNotExist(err) {
return fmt.Errorf("rbd: %s failed to check mountpoint", globalPDPath)
}
if !notMnt {
return nil
}
if err := os.MkdirAll(globalPDPath, 0750); err != nil {
return fmt.Errorf("rbd: failed to mkdir %s, error", globalPDPath)
}
// fence off other mappers
if err := util.fencing(b); err != nil {
// rbd unmap before exit
b.plugin.execCommand("rbd", []string{"unmap", devicePath})
return fmt.Errorf("rbd: image %s is locked by other nodes", b.Image)
}
// rbd lock remove needs ceph and image config
// but kubelet doesn't get them from apiserver during teardown
// so persit rbd config so upon disk detach, rbd lock can be removed
// since rbd json is persisted in the same local directory that is used as rbd mountpoint later,
// the json file remains invisible during rbd mount and thus won't be removed accidentally.
util.persistRBD(b, globalPDPath)
if err = b.mounter.FormatAndMount(devicePath, globalPDPath, b.fsType, nil); err != nil {
err = fmt.Errorf("rbd: failed to mount rbd volume %s [%s] to %s, error %v", devicePath, b.fsType, globalPDPath, err)
}
return err
}
func (util *RBDUtil) DetachDisk(c rbdUnmounter, mntPath string) error {
device, cnt, err := mount.GetDeviceNameFromMount(c.mounter, mntPath)
if err != nil {
return fmt.Errorf("rbd detach disk: failed to get device from mnt: %s\nError: %v", mntPath, err)
}
if err = c.mounter.Unmount(mntPath); err != nil {
return fmt.Errorf("rbd detach disk: failed to umount: %s\nError: %v", mntPath, err)
}
// if device is no longer used, see if can unmap
if cnt <= 1 {
// rbd unmap
_, err = c.plugin.execCommand("rbd", []string{"unmap", device})
if err != nil {
return fmt.Errorf("rbd: failed to unmap device %s:Error: %v", device, err)
}
// load ceph and image/pool info to remove fencing
if err := util.loadRBD(c.rbdMounter, mntPath); err == nil {
// remove rbd lock
util.defencing(c)
}
glog.Infof("rbd: successfully unmap device %s", device)
}
return nil
}