Account Reaper
The Account Reaper removes data from deleted accounts in the
background.
An account is marked for deletion by a reseller issuing a
DELETE request on the account’s storage URL. This simply puts
the value DELETED into the status column of the account_stat
table in the account database (and replicas), indicating the
data for the account should be deleted later.
There is normally no set retention time and no undelete; it
is assumed the reseller will implement such features and only
call DELETE on the account once it is truly desired the
account’s data be removed. However, in order to protect the
Swift cluster accounts from an improper or mistaken delete
request, you can set a delay_reaping value in the
[account-reaper] section of the account-server.conf to delay
the actual deletion of data. At this time, there is no utility
to undelete an account; one would have to update the account
database replicas directly, setting the status column to an
empty string and updating the put_timestamp to be greater than
the delete_timestamp. (On the TODO list is writing a utility
to perform this task, preferably through a ReST call.)
The account reaper runs on each account server and scans the
server occasionally for account databases marked for deletion.
It will only trigger on accounts that server is the primary
node for, so that multiple account servers aren’t all trying
to do the same work at the same time. Using multiple servers
to delete one account might improve deletion speed, but
requires coordination so they aren’t duplicating efforts. Speed
really isn’t as much of a concern with data deletion and large
accounts aren’t deleted that often.
The deletion process for an account itself is pretty
straightforward. For each container in the account, each
object is deleted and then the container is deleted. Any
deletion requests that fail won’t stop the overall process,
but will cause the overall process to fail eventually (for
example, if an object delete times out, the container won’t be
able to be deleted later and therefore the account won’t be
deleted either). The overall process continues even on a
failure so that it doesn’t get hung up reclaiming cluster
space because of one troublesome spot. The account reaper will
keep trying to delete an account until it eventually becomes
empty, at which point the database reclaim process within the
db_replicator will eventually remove the database
files.
Sometimes a persistent error state can prevent some object
or container from being deleted. If this happens, you will see
a message such as “Account <name> has not been reaped
since <date>” in the log. You can control when this is
logged with the reap_warn_after value in the [account-reaper]
section of the account-server.conf file. By default this is 30
days.