Comment 4 for bug 1789828

@zhhuabj see my above comment. I believe that the error you saw has actually been resolved and backported to ocata (i.e. the bug ref'd by @gorka) but there is still a related bug in the rbd driver which is not yet fixed. I am able to 100% repro this issue by deploying Queens, creating 100 volumes then deleting them all at once. The error in the logs is https://pastebin.ubuntu.com/p/zBFHPffzgh/ which is the same exception that you mentioned but is raised in a different place.