Comment 0 for bug 1821696

Description
===========
We hit this bug after doing a complete cluster shutdown due to server room maintenance. The bug is however more easily reproducible.

When cold starting an instance with an encrypted volume attached, it fails so start with a VolumeEncryptionNotSupported error.

https://github.com/openstack/os-brick/blob/stable/rocky/os_brick/encryptors/cryptsetup.py#L52

Steps to reproduce
==================

* Deploy Openstack with Barbican support using Kolla.
* Create an encrypted volume type
* Create an encrypted volume
* Create an instance and attach the encrypted folder
* Enjoy your new instance and volume, install software and store data
* In our case, we shut down the entire cluster and restarted it again. First all instances were stopped in Horizon using Shut down instance command. We use Ceph so we then stopped that using these procedures https://ceph.com/planet/how-to-do-a-ceph-cluster-maintenance-shutdown/ and then shut down the compute / storage nodes and then the controller nodes one by one. Then we started the cluster in the reverse order, verified all services were up and running, examined logs and then started the instances. Instances without encrypted volumes started fine.
* Instances with encrypted volumes fail to start with VolumeEncryptionNotSupported.

Note: It is possible to recreate the problem by using a Hard Reboot (possibly related https://bugs.launchpad.net/nova/+bug/1597234) or by shutting down instances and then restarting all Openstack services on that compute node.

Expected results
================
Instances with encrypted volumes should start fine, even after a Hard Reboot or a complete cluster shutdown.

Actual results
==============
Instances with encrypted volumes failed to start with VolumeEncryptionNotSupported

https://pastebin.com/mvMbJQRb

Environment
===========

1. Openstack version
Environment is established by Kolla (Rocky release).

2. Hypervisor
KVM on RHEL

3. Storage type
Ceph using Kolla (Rocky release)

Analysis
========
There seems to be a problem related to this code not behaving as expected:

https://github.com/openstack/nova/blob/stable/rocky/nova/virt/libvirt/driver.py#L1049

It seems that it is expected that the exception should be ignored and logged, but for some reason, the `ctxt.reraise = False` does not work as expected:

self.force_reraise() is called in https://github.com/openstack/oslo.utils/blob/stable/rocky/oslo_utils/excutils.py#L220 which it should not have hit since `reraise` is expected to be `False`.

We did some hacking and just swallowed the exception by commenting out the `excutils.save_and_reraise_exception()` section and replacing it with a simple `pass`.

Then the instance booted - but it could not boot from the image. But, it was then possible to remove the encrypted volume attachment, reboot the server and then reattach the encrypted volume.