On 12/12/2014 08:54 PM, melanie witt wrote:
Hi everybody,
At some point, our db archiving functionality got broken because there was a
change to stop ever deleting instance system metadata [1]. For those
unfamiliar, the 'nova-manage db archive_deleted_rows' is the thing that moves
all soft-deleted (deleted=nonzero) rows to the shadow tables. This is a
periodic cleaning that operators can do to maintain performance (as things can
get sluggish when deleted=nonzero rows accumulate).
The change was made because instance_type data still needed to be read even after
instances had been deleted, because we allow admin to view deleted instances. I saw a bug
[2] and two patches [3][4] which aimed to fix this by changing back to soft-deleting
instance sysmeta when instances are deleted, and instead allow
read_deleted="yes" for the things that need to read instance_type for deleted
instances present in the db.
My question is, is this approach okay? If so, I'd like to see these patches
revive so we can have our db archiving working again. :) I think there's likely
something I'm missing about the approach, so I'm hoping people who know more
about instance sysmeta than I do, can chime in on how/if we can fix this for db
archiving. Thanks.
I looked briefly into tackling this as well a while back. The tricky
piece that I hit is what system_metadata should be available when
read_deleted='yes'. Is it okay for it to be all deleted system_metadata
or should it only be the system_metadata that was deleted at the same
time as the instance? I didn't get to dig in enough to answer that.
Also there are periodic tasks that query for deleted instances so those
might need to pull system_metadata in addition to the API.
[1] https://bugs.launchpad.net/nova/+bug/1185190
[2] https://bugs.launchpad.net/nova/+bug/1226049
[3] https://review.openstack.org/#/c/110875/
[4] https://review.openstack.org/#/c/109201/
melanie (melwitt)
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