The timeout value in external-provisioner is fairly low. It's not
uncommon that it times out and retries before the rbdplugin is done
with CreateVolume. rbdplugin has to serialize calls and ensure that
they are idempotent to deal with this.
When the initial DeleteVolume times out (as it does on slow clusters
due to the low 10 second limit), the external-provisioner calls it
again. The CSI standard requires the second call to succeed if the
volume has been deleted in the meantime. This didn't work because
DeleteVolume returned an error when failing to find the volume info
file:
rbdplugin: E1008 08:05:35.631783 1 utils.go:100] GRPC error: rbd: open err /var/lib/kubelet/plugins/csi-rbdplugin/controller/csi-rbd-622a252c-cad0-11e8-9112-deadbeef0101.json/open /var/lib/kubelet/plugins/csi-rbdplugin/controller/csi-rbd-622a252c-cad0-11e8-9112-deadbeef0101.json: no such file or directory
The fix is to treat a missing volume info file as "volume already
deleted" and return success. To detect this, the original os error
must be wrapped, otherwise the caller of loadVolInfo cannot determine
the root cause.
Note that further work may be needed to make the driver really
resilient, for example there are probably concurrency issues.
But for now this fixes: #82
