K
Q

Timeout mounting PVC volume to pod

4/4/2018

I am trying to deploy a stateful set mounted on a Persistent Volume.

I installed Kubernetes on AWS via kops.

$ kubectl version
Client Version: version.Info{Major:"1", Minor:"9", GitVersion:"v1.9.3", GitCommit:"d2835416544f298c919e2ead3be3d0864b52323b", GitTreeState:"clean", BuildDate:"2018-02-07T12:22:21Z", GoVersion:"go1.9.2", Compiler:"gc", Platform:"linux/amd64"}
Server Version: version.Info{Major:"1", Minor:"9", GitVersion:"v1.9.3", GitCommit:"d2835416544f298c919e2ead3be3d0864b52323b", GitTreeState:"clean", BuildDate:"2018-02-07T11:55:20Z", GoVersion:"go1.9.2", Compiler:"gc", Platform:"linux/amd64"}

According to this issue I need to create the PVC first:

kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: zk-data-claim
spec:
  storageClassName: default
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 2Gi
---
kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: zk-logs-claim
spec:
  storageClassName: default
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 2Gi

The default storage class exists, and the PVC binds a PV successfully:

$ kubectl get sc
NAME            PROVISIONER             AGE
default         kubernetes.io/aws-ebs   20d
gp2 (default)   kubernetes.io/aws-ebs   20d
ssd (default)   kubernetes.io/aws-ebs   20d

$ kubectl get pvc
NAME            STATUS    VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS   AGE
zk-data-claim   Bound     pvc-5584fdf7-3853-11e8-a73b-02bb35448afe   2Gi        RWO            default        11m
zk-logs-claim   Bound     pvc-5593e249-3853-11e8-a73b-02bb35448afe   2Gi        RWO            default        11m

I can see these two volumes in the EC2 EBS Volumes list as "available" at first, but then later becomes "in-use".

And then ingest it in my StatefulSet

apiVersion: apps/v1beta1
kind: StatefulSet
metadata:
  name: zk
spec:
  serviceName: zk-cluster
  replicas: 3
  template:
    metadata:
      labels:
        app: zookeeper
    spec:
      volumes:
        - name: zk-data
          persistentVolumeClaim:
            claimName: zk-data-claim
        - name: zk-logs
          persistentVolumeClaim:
            claimName: zk-logs-claim

      containers:
      ....
        volumeMounts:
        - name: zk-data
          mountPath: /opt/zookeeper/data
        - name: zk-logs
          mountPath: /opt/zookeeper/logs

Which fails with

Unable to mount volumes for pod "zk-0_default(83b8dc93-3850-11e8-a73b-02bb35448afe)": timeout expired waiting for volumes to attach/mount for pod "default"/"zk-0". list of unattached/unmounted volumes=[zk-data zk-logs]

I'm working in the default namespace.

Any ideas what could be causing this failure?

-- Roman
amazon-web-services
kubernetes

Similar Questions

Kubernetes Pod/Service Architecture
Kubernetes Pods Always ContainerCreating
Cassandra timeout during write query at consistency QUORUM
Connect to Kubernetes cluster without using gcloud sdk

2 Answers

4/5/2018

Yeah, that is a very, very well known problem with AWS and kubernetes. Most often it is caused by a stale directory on another Node causing the EBS volume to still be "in use" from the other Node's perspective, and thus the Linux machine will not turn loose of the device when requested by the AWS API. You will see plenty of chatter about that in both kubelet.service journals, on the machine with the EBS and the machine that wants the EBS.

It has been my experience that only ssh-ing into the Node where the EBS volume is currently attached, finding the mount(s), unmounting them, and then waiting for the exponential back-off timer to expire will solve that :-(

The hand-waving version is:

## cleaning up stale docker containers might not be a terrible idea
docker rm $(docker ps -aq -f status=exited)

## identify any (and there could very well be multiple) mounts
## of the EBS device-name
mount | awk '/dev\/xvdf/ {print $2}' | xargs umount

## or sometimes kubernetes will actually name the on-disk directory ebs~ so:
mount | awk '/ebs~something/{print $2}' | xargs umount

You may experience some success involving lsof in that process, too, but hopefully(!) cleaning up the exited containers will remove the need for such a thing.

-- mdaniel
Source: StackOverflow
4/6/2018

The problem was that my cluster was made with C5 nodes. C5 and M5 nodes follow a different naming convention (NVMe), and the naming is not recognised.

Recreate the cluster with t2 type nodes.

-- Roman
Source: StackOverflow