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Fix AWS eventual consistency of AttachDisk

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AWS eventual consistency can go back in time. It can return that a volume
is detached and then that it is attached.

When this happens during attachment of the same volume to the same node,
but with a different device name, retry DescribeVolumes a few times before
reporting an error. 10 retries should be enough to get a consistent result.
This commit is contained in:
Jan Safranek 2019-11-26 18:22:48 +01:00
parent 036cf78b51
commit 4dd6fd4480
1 changed files with 28 additions and 10 deletions
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38
staging/src/k8s.io/legacy-cloud-providers/aws/aws.go
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@ -2105,17 +2105,18 @@ func (c *Cloud) applyUnSchedulableTaint(nodeName types.NodeName, reason string)
// waitForAttachmentStatus polls until the attachment status is the expected value
// On success, it returns the last attachment state.
func (d *awsDisk) waitForAttachmentStatus(status string) (*ec2.VolumeAttachment, error) {
func (d *awsDisk) waitForAttachmentStatus(status string, expectedDevice string) (*ec2.VolumeAttachment, error) {
backoff := wait.Backoff{
Duration: volumeAttachmentStatusPollDelay,
Factor: volumeAttachmentStatusFactor,
Steps: volumeAttachmentStatusSteps,
}
// Because of rate limiting, we often see errors from describeVolume
// Because of rate limiting, we often see errors from describeVolume.
// Or AWS eventual consistency returns unexpected data.
// So we tolerate a limited number of failures.
// But once we see more than 10 errors in a row, we return the error
describeErrorCount := 0
// But once we see more than 10 errors in a row, we return the error.
errorCount := 0
// Attach/detach usually takes time. It does not make sense to start
// polling DescribeVolumes before some initial delay to let AWS
@ -2144,8 +2145,8 @@ func (d *awsDisk) waitForAttachmentStatus(status string) (*ec2.VolumeAttachment,
return false, err
}
}
describeErrorCount++
if describeErrorCount > volumeAttachmentStatusConsecutiveErrorLimit {
errorCount++
if errorCount > volumeAttachmentStatusConsecutiveErrorLimit {
// report the error
return false, err
}
@ -2154,8 +2155,6 @@ func (d *awsDisk) waitForAttachmentStatus(status string) (*ec2.VolumeAttachment,
return false, nil
}
describeErrorCount = 0
if len(info.Attachments) > 1 {
// Shouldn't happen; log so we know if it is
klog.Warningf("Found multiple attachments for volume %q: %v", d.awsID, info)
@ -2177,11 +2176,29 @@ func (d *awsDisk) waitForAttachmentStatus(status string) (*ec2.VolumeAttachment,
if attachmentStatus == "" {
attachmentStatus = "detached"
}
if attachment != nil && expectedDevice != "" {
device := aws.StringValue(attachment.Device)
if device != "" && device != expectedDevice {
// AWS eventual consistency can go back in time.
// For example, we're waiting for a volume to be attached as /dev/xvdba, but AWS can tell us it's
// attached as /dev/xvdbb, where it was attached before and it was already detached.
// Retry couple of times, hoping AWS starts reporting the right status.
klog.Warningf("Expected device %s %s, but found device %s %s", expectedDevice, status, device, attachmentStatus)
errorCount++
if errorCount > volumeAttachmentStatusConsecutiveErrorLimit {
// report the error
return false, fmt.Errorf("attachment of disk %q failed: requested device %q but found %q", d.name, expectedDevice, device)
}
return false, nil
}
}
if attachmentStatus == status {
// Attachment is in requested state, finish waiting
return true, nil
}
// continue waiting
errorCount = 0
klog.V(2).Infof("Waiting for volume %q state: actual=%s, desired=%s", d.awsID, attachmentStatus, status)
return false, nil
})
@ -2321,7 +2338,7 @@ func (c *Cloud) AttachDisk(diskName KubernetesVolumeID, nodeName types.NodeName)
klog.V(2).Infof("AttachVolume volume=%q instance=%q request returned %v", disk.awsID, awsInstance.awsID, attachResponse)
}
attachment, err := disk.waitForAttachmentStatus("attached")
attachment, err := disk.waitForAttachmentStatus("attached", ec2Device)
if err != nil {
if err == wait.ErrWaitTimeout {
@ -2341,6 +2358,7 @@ func (c *Cloud) AttachDisk(diskName KubernetesVolumeID, nodeName types.NodeName)
return "", fmt.Errorf("unexpected state: attachment nil after attached %q to %q", diskName, nodeName)
}
if ec2Device != aws.StringValue(attachment.Device) {
// Already checked in waitForAttachmentStatus(), but just to be sure...
return "", fmt.Errorf("disk attachment of %q to %q failed: requested device %q but found %q", diskName, nodeName, ec2Device, aws.StringValue(attachment.Device))
}
if awsInstance.awsID != aws.StringValue(attachment.InstanceId) {
@ -2398,7 +2416,7 @@ func (c *Cloud) DetachDisk(diskName KubernetesVolumeID, nodeName types.NodeName)
return "", errors.New("no response from DetachVolume")
}
attachment, err := diskInfo.disk.waitForAttachmentStatus("detached")
attachment, err := diskInfo.disk.waitForAttachmentStatus("detached", "")
if err != nil {
return "", err
}