Pod stuck in Terminating if a configmap is mounted with subPath

[cezarsa]

What happened:

When I create a pod which includes a configmap volume and if the volume mount uses a subPath it's not possible delete the Pod, it stays in Terminating forever.
This is a weird one and it only seems to happen on Mac, colleagues on Linux were unable to reproduce, so it's possibly a docker issue.

What you expected to happen:

I expected the Pod to be deleted after a delete call.

How to reproduce it (as minimally and precisely as possible):

With the following yaml as example.yaml:

apiVersion: v1
kind: Pod
metadata:
  name: test-terminating
spec:
  containers:
  - command: ["sleep", "10000000000"]
    image: busybox
    name: test
    volumeMounts:
    - mountPath: /xyz
      name: cmap
      subPath: abc
  volumes:
  - configMap:
      name: test-terminating
    name: cmap
---
apiVersion: v1
kind: ConfigMap
metadata:
  name: test-terminating
data:
  abc: "xyz"

Run:

$ kind create cluster
$ export KUBECONFIG="$(kind get kubeconfig-path --name="kind")"
$ kubectl apply -f example.yaml
$ kubectl wait --for=condition=Ready pod test-terminating
$ kubectl delete pod test-terminating # This will hang forever!!!

After a while it's possible to see that the pod is still Terminating:

$ kubectl get pod
NAME               READY   STATUS        RESTARTS   AGE
test-terminating   0/1     Terminating   0          28m

Anything else we need to know?:

The problem only seems to happen on MacOS, on Linux I was unable to reproduce, the pod is successfully deleted.

Environment:

• kind version: (use kind version):

$ kind version
v0.4.0

• Kubernetes version: (use kubectl version):

$ kubectl version
Client Version: version.Info{Major:"1", Minor:"15", GitVersion:"v1.15.2", GitCommit:"f6278300bebbb750328ac16ee6dd3aa7d3549568", GitTreeState:"clean", BuildDate:"2019-08-05T16:54:35Z", GoVersion:"go1.12.7", Compiler:"gc", Platform:"darwin/amd64"}
Server Version: version.Info{Major:"1", Minor:"15", GitVersion:"v1.15.0", GitCommit:"e8462b5b5dc2584fdcd18e6bcfe9f1e4d970a529", GitTreeState:"clean", BuildDate:"2019-06-25T23:41:27Z", GoVersion:"go1.12.5", Compiler:"gc", Platform:"linux/amd64"}

• Docker version: (use docker info):

$ docker info
Client:
 Debug Mode: false

Server:
 Containers: 1
  Running: 1
  Paused: 0
  Stopped: 0
 Images: 1
 Server Version: 19.03.1
 Storage Driver: overlay2
  Backing Filesystem: extfs
  Supports d_type: true
  Native Overlay Diff: true
 Logging Driver: json-file
 Cgroup Driver: cgroupfs
 Plugins:
  Volume: local
  Network: bridge host ipvlan macvlan null overlay
  Log: awslogs fluentd gcplogs gelf journald json-file local logentries splunk syslog
 Swarm: inactive
 Runtimes: runc
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: 894b81a4b802e4eb2a91d1ce216b8817763c29fb
 runc version: 425e105d5a03fabd737a126ad93d62a9eeede87f
 init version: fec3683
 Security Options:
  seccomp
   Profile: default
 Kernel Version: 4.9.184-linuxkit
 Operating System: Docker Desktop
 OSType: linux
 Architecture: x86_64
 CPUs: 2
 Total Memory: 1.952GiB
 Name: docker-desktop
 ID: F4T7:DRSI:2M7J:5NHO:M4NR:GQUU:OKLV:KQQI:7CUQ:6XUE:ONRB:4EFF
 Docker Root Dir: /var/lib/docker
 Debug Mode: true
  File Descriptors: 34
  Goroutines: 49
  System Time: 2019-08-14T19:28:34.768985516Z
  EventsListeners: 2
 HTTP Proxy: gateway.docker.internal:3128
 HTTPS Proxy: gateway.docker.internal:3129
 Registry: https://index.docker.io/v1/
 Labels:
 Experimental: false
 Insecure Registries:
  127.0.0.0/8
 Live Restore Enabled: false
 Product License: Community Engine

• OS (e.g. from /etc/os-release):

$ sw_vers
ProductName:	Mac OS X
ProductVersion:	10.14.4
BuildVersion:	18E226

[BenTheElder]

I can replicate this and see the error.

Aug 14 22:54:21 kind-control-plane kubelet[215]: E0814 22:54:21.251200 215 nestedpendingoperations.go:270] Operation for ""kubernetes.io/configmap/69d410fd-a144-435f-a1cb-7b7d9ce109bc-cmap" ("69d410fd-a144-435f-a1cb-7b7d9ce109bc")" failed. No retries permitted until 2019-08-14 22:56:23.251137 +0000 UTC m=+391.229059401 (durationBeforeRetry 2m2s). Error: "error cleaning subPath mounts for volume "cmap" (UniqueName: "kubernetes.io/configmap/69d410fd-a144-435f-a1cb-7b7d9ce109bc-cmap") pod "69d410fd-a144-435f-a1cb-7b7d9ce109bc" (UID: "69d410fd-a144-435f-a1cb-7b7d9ce109bc") : error processing /var/lib/kubelet/pods/69d410fd-a144-435f-a1cb-7b7d9ce109bc/volume-subpaths/cmap/test: error cleaning subpath mount /var/lib/kubelet/pods/69d410fd-a144-435f-a1cb-7b7d9ce109bc/volume-subpaths/cmap/test/0: Unmount failed: exit status 32\nUnmounting arguments: /var/lib/kubelet/pods/69d410fd-a144-435f-a1cb-7b7d9ce109bc/volume-subpaths/cmap/test/0\nOutput: umount: /var/lib/kubelet/pods/69d410fd-a144-435f-a1cb-7b7d9ce109bc/volume-subpaths/cmap/test/0: not mounted.\n\n"

[aojea]

Are there more logs associated? journalctl | grep cmap

What happens if you try to unmount it manually ?

mount | grep cmap (obtain mount point)
umount -v /var/lib/kubelet/pods/UUID/volume-subpaths/cmap/test/0

[BenTheElder]

I'm pretty sure I know what this is, just ran out of time to patch it yesterday and then today we've had some upstream things to patch :-)

There are more logs yes, but that's the relevant part. If you run umount manually you won't get a different result. This is a bug in kind.

[BenTheElder]

This should be fixed (and probably other things!) with the latest version, please let me know if you see this again. We'll be cutting a new release soon but need to check on some unrelated issues 😅

[BenTheElder]

Also: Thanks for reporting this, and for the detailed report and minimal reproducer!