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AWS: Use a strongly typed mountDevice

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We've had problems in the past from using a string with passing the
wrong value when detaching; stronger typing would have caught this for
us.
This commit is contained in:
Justin Santa Barbara 2016-01-07 23:52:05 -05:00
parent 7ca0fa431b
commit 03900b1dc9
1 changed files with 35 additions and 27 deletions
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62
pkg/cloudprovider/providers/aws/aws.go
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@ -802,12 +802,16 @@ func (self *AWSCloud) GetZone() (cloudprovider.Zone, error) {
type awsInstanceType struct {
}
// Used to represent a mount device for attaching an EBS volume
// This should be stored as a single letter (i.e. c, not sdc or /dev/sdc)
type mountDevice string
// TODO: Also return number of mounts allowed?
func (self *awsInstanceType) getEBSMountDevices() []string {
func (self *awsInstanceType) getEBSMountDevices() []mountDevice {
// See: https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/block-device-mapping-concepts.html
devices := []string{}
devices := []mountDevice{}
for c := 'f'; c <= 'p'; c++ {
devices = append(devices, fmt.Sprintf("%c", c))
devices = append(devices, mountDevice(fmt.Sprintf("%c", c)))
}
return devices
}
@ -825,7 +829,7 @@ type awsInstance struct {
// We must cache because otherwise there is a race condition,
// where we assign a device mapping and then get a second request before we attach the volume
deviceMappings map[string]string
deviceMappings map[mountDevice]string
}
func newAWSInstance(ec2 EC2, awsID, nodeName string) *awsInstance {
@ -864,9 +868,10 @@ func (self *awsInstance) getInfo() (*ec2.Instance, error) {
return instances[0], nil
}
// Assigns an unused mountpoint (device) for the specified volume.
// If the volume is already assigned, this will return the existing mountpoint and true
func (self *awsInstance) assignMountpoint(volumeID string) (mountpoint string, alreadyAttached bool, err error) {
// Gets the mountDevice already assigned to the volume, or assigns an unused mountDevice.
// If the volume is already assigned, this will return the existing mountDevice with alreadyAttached=true.
// Otherwise the mountDevice is assigned by finding the first available mountDevice, and it is returned with alreadyAttached=false.
func (self *awsInstance) getMountDevice(volumeID string) (assigned mountDevice, alreadyAttached bool, err error) {
instanceType := self.getInstanceType()
if instanceType == nil {
return "", false, fmt.Errorf("could not get instance type for instance: %s", self.awsID)
@ -884,35 +889,38 @@ func (self *awsInstance) assignMountpoint(volumeID string) (mountpoint string, a
if err != nil {
return "", false, err
}
deviceMappings := map[string]string{}
deviceMappings := map[mountDevice]string{}
for _, blockDevice := range info.BlockDeviceMappings {
mountpoint := orEmpty(blockDevice.DeviceName)
if strings.HasPrefix(mountpoint, "/dev/sd") {
mountpoint = mountpoint[7:]
name := aws.StringValue(blockDevice.DeviceName)
if strings.HasPrefix(name, "/dev/sd") {
name = name[7:]
}
if strings.HasPrefix(mountpoint, "/dev/xvd") {
mountpoint = mountpoint[8:]
if strings.HasPrefix(name, "/dev/xvd") {
name = name[8:]
}
deviceMappings[mountpoint] = orEmpty(blockDevice.Ebs.VolumeId)
if len(name) != 1 {
glog.Warningf("Unexpected EBS DeviceName: %q", aws.StringValue(blockDevice.DeviceName))
}
deviceMappings[mountDevice(name)] = aws.StringValue(blockDevice.Ebs.VolumeId)
}
self.deviceMappings = deviceMappings
}
// Check to see if this volume is already assigned a device on this machine
for mountpoint, mappingVolumeID := range self.deviceMappings {
for mountDevice, mappingVolumeID := range self.deviceMappings {
if volumeID == mappingVolumeID {
glog.Warningf("Got assignment call for already-assigned volume: %s@%s", mountpoint, mappingVolumeID)
return mountpoint, true, nil
glog.Warningf("Got assignment call for already-assigned volume: %s@%s", mountDevice, mappingVolumeID)
return mountDevice, true, nil
}
}
// Check all the valid mountpoints to see if any of them are free
valid := instanceType.getEBSMountDevices()
chosen := ""
for _, device := range valid {
_, found := self.deviceMappings[device]
chosen := mountDevice("")
for _, mountDevice := range valid {
_, found := self.deviceMappings[mountDevice]
if !found {
chosen = device
chosen = mountDevice
break
}
}
@ -928,7 +936,7 @@ func (self *awsInstance) assignMountpoint(volumeID string) (mountpoint string, a
return chosen, false, nil
}
func (self *awsInstance) releaseMountDevice(volumeID string, mountDevice string) {
func (self *awsInstance) releaseMountDevice(volumeID string, mountDevice mountDevice) {
self.mutex.Lock()
defer self.mutex.Unlock()
@ -1130,24 +1138,24 @@ func (c *AWSCloud) AttachDisk(instanceName string, diskName string, readOnly boo
return "", errors.New("AWS volumes cannot be mounted read-only")
}
mountpoint, alreadyAttached, err := awsInstance.assignMountpoint(disk.awsID)
mountDevice, alreadyAttached, err := awsInstance.getMountDevice(disk.awsID)
if err != nil {
return "", err
}
// Inside the instance, the mountpoint always looks like /dev/xvdX (?)
hostDevice := "/dev/xvd" + mountpoint
hostDevice := "/dev/xvd" + string(mountDevice)
// In the EC2 API, it is sometimes is /dev/sdX and sometimes /dev/xvdX
// We are running on the node here, so we check if /dev/xvda exists to determine this
ec2Device := "/dev/xvd" + mountpoint
ec2Device := "/dev/xvd" + string(mountDevice)
if _, err := os.Stat("/dev/xvda"); os.IsNotExist(err) {
ec2Device = "/dev/sd" + mountpoint
ec2Device = "/dev/sd" + string(mountDevice)
}
attached := false
defer func() {
if !attached {
awsInstance.releaseMountDevice(disk.awsID, mountpoint)
awsInstance.releaseMountDevice(disk.awsID, mountDevice)
}
}()