16 Common issues #

After you verify the basic health of the running pods, next you will want to run Ceph tools for status of the storage components. There are two ways to run the Ceph tools, either in the Rook toolbox or inside other Rook pods that are already running.

kubectl@adm > kubectl -n rook-ceph exec -it $(kubectl -n rook-ceph get pod -l "app=rook-ceph-tools" -o jsonpath='{.items[0].metadata.name}') bash

Create a rook-ceph-tools pod to investigate the current state of Ceph. The following is an example of the output. In this case, the ceph status command would just hang and the process would need to be killed.

kubectl@adm > kubectl -n rook-ceph exec -it $(kubectl -n rook-ceph get pod -l "app=rook-ceph-tools" -o jsonpath='{.items[0].metadata.name}') bash
cephuser@adm > ceph status
^CCluster connection interrupted or timed out

Another indication is when one or more of the MON pods restart frequently. Note the “mon107” that has only been up for 16 minutes in the following output.

kubectl@adm > kubectl -n rook-ceph get all -o wide --show-all
  NAME                                 READY     STATUS    RESTARTS   AGE       IP               NODE
  po/rook-ceph-mgr0-2487684371-gzlbq   1/1       Running   0          17h       192.168.224.46   k8-host-0402
  po/rook-ceph-mon107-p74rj            1/1       Running   0          16m       192.168.224.28   k8-host-0402
  rook-ceph-mon1-56fgm                 1/1       Running   0          2d        192.168.91.135   k8-host-0404
  rook-ceph-mon2-rlxcd                 1/1       Running   0          2d        192.168.123.33   k8-host-0403
  rook-ceph-osd-bg2vj                  1/1       Running   0          2d        192.168.91.177   k8-host-0404
  rook-ceph-osd-mwxdm                  1/1       Running   0          2d        192.168.123.31   k8-host-0403

What is happening here is that the MON pods are restarting and one or more of the Ceph daemons are not getting configured with the proper cluster information. This is commonly the result of not specifying a value for dataDirHostPath in your Cluster CRD.

The dataDirHostPath setting specifies a path on the local host for the Ceph daemons to store configuration and data. Setting this to a path like /var/lib/rook, reapplying your cluster CRD and restarting all the Ceph daemons (MON, MGR, OSD, RGW) should solve this problem. After the Object Gateway daemons have been restarted, it is advisable to restart the rook-tools pod.

When the operator is starting a cluster, the operator will start one MON at a time and check that they are healthy before continuing to bring up all three MONs. If the first MON is not detected healthy, the operator will continue to check until it is healthy. If the first MON fails to start, a second and then a third MON may attempt to start. However, they will never form a quorum, and orchestration will be blocked from proceeding.

The likely causes for the MON health not being detected:

kubectl@adm > kubectl -n rook-ceph logs -l app=rook-ceph-operator

  2018-01-21 21:47:32.375833 I | exec: Running command: ceph mon_status --cluster=rook --conf=/var/lib/rook/rook-ceph/rook.config --keyring=/var/lib/rook/rook-ceph/client.admin.keyring --format json --out-file /tmp/442263890
  2018-01-21 21:52:35.370533 I | exec: 2018-01-21 21:52:35.071462 7f96a3b82700  0 monclient(hunting): authenticate timed out after 300
  2018-01-21 21:52:35.071462 7f96a3b82700  0 monclient(hunting): authenticate timed out after 300
  2018-01-21 21:52:35.071524 7f96a3b82700  0 librados: client.admin authentication error (110) Connection timed out
  2018-01-21 21:52:35.071524 7f96a3b82700  0 librados: client.admin authentication error (110) Connection timed out
  [errno 110] error connecting to the cluster

kubectl@adm > kubectl -n rook-ceph get pod -l app=rook-ceph-mon
NAME                                READY     STATUS               RESTARTS   AGE
rook-ceph-mon-a-69fb9c78cd-58szd    1/1       CrashLoopBackOff     2          47s

kubectl@adm > kubectl -n rook-ceph describe pod -l mon=rook-ceph-mon0
[...]
Last State:    Terminated
Reason:    Error
Message:    The keyring does not match the existing keyring in /var/lib/rook/rook-ceph-mon0/data/keyring.
You may need to delete the contents of dataDirHostPath on the host from a previous deployment.
[...]

NAME                               READY   STATUS    RESTARTS   AGE
rook-ceph-mon-a-7d9fd97d9b-cdq7g   1/1     Running   0          10m
rook-ceph-mon-d-77df8454bd-r5jwr   1/1     Running   0          9m2s
rook-ceph-mon-f-58b4f8d9c7-89lgs   1/1     Running   0          7m38s

16.1.3.2.4 Identifying the solution #

 

This is a common problem reinitializing the Rook cluster when the local directory used for persistence has not been purged. This directory is the dataDirHostPath setting in the cluster CRD, and is typically set to /var/lib/rook. To fix the issue, you will need to delete all components of Rook and then delete the contents of /var/lib/rook (or the directory specified by dataDirHostPath) on each of the hosts in the cluster. Then, when the cluster CRD is applied to start a new cluster, the rook-operator should start all the pods as expected.

Important

Deleting the dataDirHostPath folder is destructive to the storage. Only delete the folder if you are trying to permanently purge the Rook cluster.

When you create a PVC based on a Rook storage class, it stays pending indefinitely.

For the Wordpress example, you might see two PVCs in the pending state.

kubectl@adm > kubectl get pvc
NAME             STATUS    VOLUME   CAPACITY   ACCESS MODES   STORAGECLASS      AGE
mysql-pv-claim   Pending                                      rook-ceph-block   8s
wp-pv-claim      Pending                                      rook-ceph-block   16s

There are two common causes for the PVCs staying in the pending state:

cephuser@adm > ceph status
  cluster:
  id:     a0452c76-30d9-4c1a-a948-5d8405f19a7c
  health: HEALTH_OK

  services:
  mon: 3 daemons, quorum a,b,c (age 11m)
  mgr: a(active, since 10m)
  osd: 1 osds: 1 up (since 46s), 1 in (since 109m)

kubectl@adm > kubectl -n rook-ceph get pod -l app=rook-ceph-osd-prepare
NAME                                 ...  READY   STATUS      RESTARTS   AGE
rook-ceph-osd-prepare-minikube-9twvk   0/2     Completed   0          30m

kubectl@adm > kubectl -n rook-ceph get pod -l app=csi-rbdplugin-provisioner

kubectl@adm > kubectl -n rook-ceph logs csi-cephfsplugin-provisioner-d77bb49c6-q9hwq csi-provisioner

If the OSD prepare logs did not give you enough clues about why the OSDs were not being created, review your cluster.yaml configuration. The common mistakes include:

When an OSD starts, the device or directory will be configured for consumption. If there is an error with the configuration, the pod will crash and you will see the CrashLoopBackoff status for the pod. Look in the OSD pod logs for an indication of the failure.

kubectl@adm > kubectl -n rook-ceph logs rook-ceph-osd-fl8fs

One common case for failure is that you have re-deployed a test cluster and some state may remain from a previous deployment. If your cluster is larger than a few nodes, you may get lucky enough that the monitors were able to start and form a quorum. However, now the OSDs pods may fail to start due to the old state. Looking at the OSD pod logs, you will see an error about the file already existing.

kubectl -n rook-ceph logs rook-ceph-osd-fl8fs
[...]
2017-10-31 20:13:11.187106 I | mkfs-osd0: 2017-10-31 20:13:11.186992 7f0059d62e00 -1 bluestore(/var/lib/rook/osd0) _read_fsid unparsable uuid
2017-10-31 20:13:11.187208 I | mkfs-osd0: 2017-10-31 20:13:11.187026 7f0059d62e00 -1 bluestore(/var/lib/rook/osd0) _setup_block_symlink_or_file failed to create block symlink to /dev/disk/by-partuuid/651153ba-2dfc-4231-ba06-94759e5ba273: (17) File exists
2017-10-31 20:13:11.187233 I | mkfs-osd0: 2017-10-31 20:13:11.187038 7f0059d62e00 -1 bluestore(/var/lib/rook/osd0) mkfs failed, (17) File exists
2017-10-31 20:13:11.187254 I | mkfs-osd0: 2017-10-31 20:13:11.187042 7f0059d62e00 -1 OSD::mkfs: ObjectStore::mkfs failed with error (17) File exists
2017-10-31 20:13:11.187275 I | mkfs-osd0: 2017-10-31 20:13:11.187121 7f0059d62e00 -1  ** ERROR: error creating empty object store in /var/lib/rook/osd0: (17) File exists

If the error is from the file that already exists, this is a common problem reinitializing the Rook cluster when the local directory used for persistence has not been purged. This directory is the dataDirHostPath setting in the cluster CRD and is typically set to /var/lib/rook. To fix the issue you will need to delete all components of Rook and then delete the contents of /var/lib/rook (or the directory specified by dataDirHostPath) on each of the hosts in the cluster. Then when the cluster CRD is applied to start a new cluster, the rook-operator should start all the pods as expected.

First, ensure that you have specified the devices correctly in the CRD. The cluster CRD has several ways to specify the devices that are to be consumed by the Rook storage:

Second, if Rook determines that a device is not available (has existing partitions or a formatted file system), Rook will skip consuming the devices. If Rook is not starting OSDs on the devices you expect, Rook may have skipped it for this reason. To see if a device was skipped, view the OSD preparation log on the node where the device was skipped. Note that it is completely normal and expected for OSD prepare pod to be in the completed state. After the job is complete, Rook leaves the pod around in case the logs need to be investigated.

Get the prepare pods in the cluster:

kubectl@adm > kubectl -n rook-ceph get pod -l app=rook-ceph-osd-prepare
NAME                                   READY     STATUS      RESTARTS   AGE
rook-ceph-osd-prepare-node1-fvmrp      0/1       Completed   0          18m
rook-ceph-osd-prepare-node2-w9xv9      0/1       Completed   0          22m
rook-ceph-osd-prepare-node3-7rgnv      0/1       Completed   0          22m

View the logs for the node of interest in the "provision" container:

kubectl@adm > kubectl -n rook-ceph logs rook-ceph-osd-prepare-node1-fvmrp provision

Here are some key lines to look for in the log. A device will be skipped if Rook sees it has partitions or a file system:

2019-05-30 19:02:57.353171 W | cephosd: skipping device sda that is in use
2019-05-30 19:02:57.452168 W | skipping device "sdb5": ["Used by ceph-disk"]

Other messages about a disk being unusable by Ceph include:

Insufficient space (<5GB) on vgs
Insufficient space (<5GB)
LVM detected
Has BlueStore device label
locked
read-only

A device is going to be configured:

2019-05-30 19:02:57.535598 I | cephosd: device sdc to be configured by ceph-volume

For each device configured, you will see a report in the log:

2019-05-30 19:02:59.844642 I |   Type            Path                                                    LV Size         % of device
2019-05-30 19:02:59.844651 I | ----------------------------------------------------------------------------------------------------
2019-05-30 19:02:59.844677 I |   [data]          /dev/sdc                                                7.00 GB         100%

Either update the CR with the correct settings, or clean the partitions or file system from your devices.

After the settings are updated or the devices are cleaned, trigger the operator to analyze the devices again by restarting the operator. Each time the operator starts, it will ensure all the desired devices are configured. The operator does automatically deploy OSDs in most scenarios, but an operator restart will cover any scenarios that the operator does not detect automatically.

Restart the operator to ensure devices are configured. A new pod will automatically be started when the current operator pod is deleted.

kubectl@adm > kubectl -n rook-ceph delete pod -l app=rook-ceph-operator

If it is feasible to upgrade your kernel, you should upgrade to 4.x, even better is 4.7 or above, due to a feature for CephFS added to the kernel.

If you are unable to upgrade the kernel, you need to go to each host that will consume storage and run:

modprobe rbd

This command inserts the rbd module into the kernel.

To persist this fix, you need to add the rbd kernel module to either /etc/modprobe.d/ or /etc/modules-load.d/. For both paths create a file called rbd.conf with the following content:

rbd

Now when a host is restarted, the module should be loaded automatically.

The only solution to this problem is to upgrade your kernel to 4.7 or higher. This is due to a mount flag added in kernel version 4.7, which allows choosing the file system by name.

This happens when the following conditions are satisfied.

In addition, when this problem happens, you can see the following messages in dmesg.

dmesg
...
[51717.039319] INFO: task kworker/2:1:5938 blocked for more than 120 seconds.
[51717.039361]       Not tainted 4.15.0-72-generic #81-Ubuntu
[51717.039388] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
...

This is the so-called hung_task problem and means that there is a deadlock in the kernel.

You can bypass this problem by using ext4 or any other file systems rather than XFS. The file system type can be specified with csi.storage.k8s.io/fstype in StorageClass resource.

See Chapter 5, Troubleshooting placement groups (PGs) for more information.

There is a critical flaw in OSD on LV-backed PVC. LVM metadata can be corrupted if both the host and OSD container modify it simultaneously. For example, the administrator might modify it on the host, while the OSD initialization process in a container could modify it too. In addition, if lvmetad is running, the possibility of occurrence gets higher. In this case, the change of LVM metadata in OSD container is not reflected to LVM metadata cache in host for a while.

If you still decide to configure an OSD on LVM, keep the following in mind to reduce the probability of this issue.

You can know whether the above-mentioned tag exists tag by running

#  lvs -o lv_name,lv_tags

If the lv_tag field is empty in an LV corresponding to the OSD lv_tags, this OSD encountered the problem. In this case, retire this OSD or replace with other new OSD before restarting.