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46 lines
1.4 KiB
Markdown
46 lines
1.4 KiB
Markdown
# ceph-fuse: detection of corrupted mounts and their recovery
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Mounts managed by ceph-fuse may get corrupted by e.g. the ceph-fuse process
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exiting abruptly, or its parent Node Plugin container being terminated, taking
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down its child processes with it.
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This may manifest in concerned workloads like so:
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```
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# mount | grep fuse
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ceph-fuse on /cephfs-share type fuse.ceph-fuse (rw,nosuid,nodev,relatime,user_id=0,group_id=0,allow_other)
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# ls /cephfs-share
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ls: /cephfs-share: Socket not connected
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```
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or,
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```
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# stat /home/kubelet/pods/ae344b80-3b07-4589-b1a1-ca75fa9debf2/volumes/kubernetes.io~csi/pvc-ec69de59-7823-4840-8eee-544f8261fef0/mount: transport endpoint is not connected
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```
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This feature allows CSI CephFS plugin to be able to detect if a ceph-fuse mount
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is corrupted during the volume publishing phase, and will attempt to recover it
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for the newly scheduled pod. Pods that already reside on a node whose
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ceph-fuse mountpoints were broken may still need to be restarted, however.
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## Detection
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A mountpoint is deemed corrupted if `stat()`-ing it returns one of the
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following errors:
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* `ENOTCONN`
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* `ESTALE`
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* `EIO`
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* `EACCES`
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* `EHOSTDOWN`
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## Recovery
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Once a mountpoint corruption is detected, its recovery is performed by
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remounting the volume associated with it.
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Recovery is attempted only if `/csi/mountinfo` directory is made available to
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CSI CephFS plugin (available by default in the Helm chart and Kubernetes
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manifests).
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