Local storage teardown fix #48402

ianchakeres · 2017-07-02T18:43:56Z

What this PR does / why we need it: Local storage uses bindmounts and the method IsLikelyNotMountPoint does not detect these as mountpoints. Therefore, local PVs are not properly unmounted when they are deleted.

Which issue this PR fixes: fixes #48331

Special notes for your reviewer:

You can use these e2e tests to reproduce the issue and validate the fix works appropriately #47999

The existing method IsLikelyNotMountPoint purposely does not check mountpoints reliability (

kubernetes/pkg/util/mount/mount_linux.go

Line 161 in 4c5b22d

// IsLikelyNotMountPoint determines if a directory is not a mountpoint.

), since the number of mountpoints can be large.

kubernetes/pkg/util/mount/mount.go

Line 46 in 4c5b22d

List() ([]MountPoint, error)

This implementation changes the behavior for local storage to detect mountpoints reliably, and avoids changing the behavior for any other callers to a UnmountPath.

Release note:

Fixes bind-mount teardown failure with non-mount point Local volumes (issue https://github.com/kubernetes/kubernetes/issues/48331).

ianchakeres · 2017-07-02T18:44:09Z

/sig storage

ianchakeres · 2017-07-02T18:44:20Z

@k8s-ci-robot ok to test

ianchakeres · 2017-07-02T18:46:24Z

@CallMeFoxie @msau42 @saad-ali - Here is the PR to fix #48331. Please take a look and let me know if you have any questions or comments.

CallMeFoxie · 2017-07-03T06:10:36Z

I0703 08:07:44.466131 22258 operation_generator.go:523] UnmountVolume.TearDown succeeded for volume "kubernetes.io/secret/ae9f9214-5fb5-11e7-a549-180373f4ecc0-default-token-mhn97" (OuterVolumeSpecName: "default-token-mhn97") pod "ae9f9214-5fb5-11e7-a549-180373f4ecc0" (UID: "ae9f9214-5fb5-11e7-a549-180373f4ecc0"). InnerVolumeSpecName "default-token-mhn97". PluginName "kubernetes.io/secret", VolumeGidValue ""
I0703 08:07:44.467018 22258 operation_generator.go:523] UnmountVolume.TearDown succeeded for volume "kubernetes.io/local-volume/ae9f9214-5fb5-11e7-a549-180373f4ecc0-test-affinity-test-1" (OuterVolumeSpecName: "test") pod "ae9f9214-5fb5-11e7-a549-180373f4ecc0" (UID: "ae9f9214-5fb5-11e7-a549-180373f4ecc0"). InnerVolumeSpecName "test-affinity-test-1". PluginName "kubernetes.io/local-volume", VolumeGidValue ""

looks good to me even with local self hosted storage, unmounts the volumes as it should back and forth.
cc @msau42 @saad-ali @jsafrane

jsafrane · 2017-07-03T10:11:22Z

pkg/volume/util/util.go

 	if notMnt {
 		glog.Warningf("Warning: %q is not a mountpoint, deleting", mountPath)
 		return os.Remove(mountPath)
 	}

 	// Unmount the mount path
+	glog.Warningf("Warning: %q is a mountpoint, unmounting", mountPath)


I think that lower log level should be used, it's part of a normal operation.

@jsafrane - would you like me to lower the log level for the previous statement L107 too?

No, at 107 something else happened - something unmounted a fs and left a stray directory there, e.g. kubelet crashed after unmount and before os.Remove. It's quite exceptional event.

Here on line 112 it's just normal operation, nothing suspicious.

jsafrane · 2017-07-03T15:21:50Z

lgtm to me, however I let @msau42 or @rootfs say the final word.

msau42 · 2017-07-04T22:45:54Z

pkg/util/mount/mount.go

+
+// IsNotMountPoint determines if a directory is a mountpoint.
+// It should return ErrNotExist when the directory does not exist.
+// This method uses the List() of all mountpoints


Add a comment that in particular this is can detect bind mounts of directories.

msau42 · 2017-07-04T22:47:31Z

pkg/util/mount/mount.go

+	if mountPointsErr != nil {
+		return notMnt, mountPointsErr
+	}
+	deletedFile := fmt.Sprintf("%s\\040(deleted)", file)


This parsing is implementation specific. It should be done in the the mounter implementation instead.

msau42 · 2017-07-04T22:50:47Z

pkg/volume/local/local.go

@@ -269,5 +269,5 @@ func (u *localVolumeUnmounter) TearDown() error {
 // TearDownAt unmounts the bind mount
 func (u *localVolumeUnmounter) TearDownAt(dir string) error {
 	glog.V(4).Infof("Unmounting volume %q at path %q\n", u.volName, dir)
-	return util.UnmountPath(dir, u.mounter)
+	return util.UnmountMountPoint(dir, u.mounter, true) /* extensiveMountPointCheck = true */


During mount we also call IsLikelyNotMountPoint. Need to also evaluate if that call needs to be updated too.

I modified all references of IsLikelyNotMountPoint to use IsNotMountPoint inside local.go.

ianchakeres · 2017-07-05T15:31:17Z

/retest

saad-ali · 2017-07-05T16:52:52Z

pkg/util/mount/mount.go

+// It should return ErrNotExist when the directory does not exist.
+// This method uses the List() of all mountpoints
+// It is more extensive than IsLikelyNotMountPoint
+// and it detects bind mounts in linux


Also add a comment indicating that compared to IsLikelyNotMountPoint(...), this will have a higher perf impact if the machine has a lot of mounts (since it lists all the mounts), and should not be used in critical paths unless absolutely necessary.

saad-ali · 2017-07-05T16:54:59Z

pkg/util/mount/mount.go

+	// IsNotMountPoint is more extensive than IsLikelyNotMountPoint
+	// It uses IsMountPointMatch to detect matching dir in List()
+	// It detects bind mounts in linux
+	IsNotMountPoint(file string) (bool, error)
 	// IsLikelyNotMountPoint determines if a directory is a mountpoint.
 	// It should return ErrNotExist when the directory does not exist.


The comment on the existing method sucks. Now that we're adding a similar method, let's update both to make it very crisp and clear 1) what each does, 2) what the differences between them are, and 3) when a caller should use one vs the other, and 4) what the pitfalls of each are.

saad-ali · 2017-07-05T17:07:53Z

pkg/volume/util/util.go

+
+// UnmountMountPoint is a common unmount routine that unmounts the given path and
+// deletes the remaining directory if successful.
+// if extensiveMountPointCheck is true


Also please add comment about perf implications about enabling this option.

saad-ali · 2017-07-05T17:09:27Z

pkg/volume/util/util.go

@@ -75,23 +75,41 @@ func SetReady(dir string) {
 // UnmountPath is a common unmount routine that unmounts the given path and
 // deletes the remaining directory if successful.
 func UnmountPath(mountPath string, mounter mount.Interface) error {
+	return UnmountMountPoint(mountPath, mounter, false) /* extensiveMountPointCheck = false */


Super nit:

I prefer

UnmountMountPoint(mountPath, mounter, false /* extensiveMountPointCheck */)

since it's less verbose and doesn't require you to update the value and comment if you change the value.

saad-ali · 2017-07-05T17:10:58Z

Paging @pmorie since he's familiar with this some of the mounter code (nsenter_mount in particular).

msau42 · 2017-07-10T18:29:38Z

/lgtm

saad-ali · 2017-07-10T18:30:43Z

Also, please add more descriptive release note (explain what exact bug this is fixing).

Updated release note on behalf of @ianchakeres with link to bug being fixed.

saad-ali · 2017-07-10T21:56:21Z

/test pull-kubernetes-e2e-kops-aws

wojtek-t · 2017-07-11T06:38:52Z

@saad-ali - thanks! Will create a cherrypick PR once this one is merged (but I don't have any more concerns).

ianchakeres · 2017-07-11T11:32:08Z

/test pull-kubernetes-e2e-kops-aws

ianchakeres · 2017-07-11T11:34:25Z

@saad-ali - I'm hoping that #48403 will fix pull-kubernetes-e2e-kops-aws errors we're seeing.

ianchakeres · 2017-07-11T14:59:32Z

This PR #48762 should help with docker timeout in e2e-kops-aws.

fejta · 2017-07-11T20:06:50Z

/test pull-kubernetes-e2e-kops-aws

Added IsNotMountPoint method to mount utils (pkg/util/mount/mount.go) Added UnmountMountPoint method to volume utils (pkg/volume/util/util.go) Call UnmountMountPoint method from local storage (pkg/volume/local/local.go) IsLikelyNotMountPoint behavior was not modified, so the logic/behavior for UnmountPath is not modified

ianchakeres · 2017-07-11T21:25:06Z

@saad-ali @msau42 - I just squashed the commits.

msau42 · 2017-07-11T21:29:08Z

/lgtm

k8s-github-robot · 2017-07-11T21:29:16Z

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: ianchakeres, msau42, saad-ali
We suggest the following additional approver: smarterclayton

Assign the PR to them by writing /assign @smarterclayton in a comment when ready.

Associated issue: 48331

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k8s-github-robot · 2017-07-12T03:35:29Z

Automatic merge from submit-queue

wojtek-t · 2017-07-12T12:38:35Z

#48809 constains a cherrypick of it

#48524-upstream-release-1.7 Automatic merge from submit-queue Automated cherry pick of #48402 #48524 upstream release 1.7 Cherry pick of #48524 and #48402 on release-1.7. #48524 : fix udp service blackhole problem when number of backends changes from 0 to non-0 #48402 : Local storage teardown fix

k8s-cherrypick-bot · 2017-07-18T08:13:51Z

Commit found in the "release-1.7" branch appears to be this PR. Removing the "cherrypick-candidate" label. If this is an error find help to get your PR picked.

k8s-ci-robot added the cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. label Jul 2, 2017

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ianchakeres mentioned this pull request Jul 3, 2017

LocalPV e2e test with two pods writing/reading to a shared file on one PVC #47999

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ianchakeres force-pushed the local-storage-teardown-fix branch from e8447ad to 748db25 Compare July 5, 2017 15:15

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wojtek-t mentioned this pull request Jul 12, 2017

Automated cherry pick of #48402 #48524 upstream release 1.7 #48809

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msau42 mentioned this pull request Jul 20, 2017

Allow unmounting bind-mounted directories. #49118

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This was referenced Jul 25, 2017

isLikelyNotMountPoint() function needs refactored #26996

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Have Cinder mount tasks use new kubelet functions #49786

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msau42 mentioned this pull request Jul 28, 2017

Cache mounts on the host #49793

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ianchakeres mentioned this pull request Sep 19, 2017

Fix volume remount on reboot #51985

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Local storage teardown fix #48402

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Local storage teardown fix #48402

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