We've currently disabled transactions on MySQL because they were causing
concurrency problems, so a non-transaction solution would be
preferrable.
It looks like currently, we update the user's quota by calling the
User::quota_add($bytes) function, which adds a file's size to the
usr.quotaused field. We could lessen the impact of this bug if we
instead summed up the size of all the user's files. Preferrably in a
single query, something like (although I'm not sure if this would be
kosher in MySQL):
UPDATE usr u
SET quotaused = (
SELECT sum(aff.size)
FROM
artefact_file_files aff
INNER JOIN artefact a
ON a.id = aff.artefact
WHERE
a.owner = u.id
)
WHERE
u.id = ?
Of course you could still get race conditions, but they'd only last
until the next pageload when we do "SELECT * FROM usr" (assuming that I
am correctly remembering that we do that on each page and don't cache it
in the session).
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https://bugs.launchpad.net/bugs/1606749
Title:
Inconsistent file quota usage
Status in Mahara:
Confirmed
Bug description:
Mahara: 16.04.2
DB: Postgres
OS: Linux
Browser: various
File quota calculations are not syncing correctly for file upload when
using multiple devices at the same time.
This lets users surpass their quota by using different computers at
the same time.
I've also been able to replicate it by uploading multiple files at
once. The usr.quotaused field doesn't get correctly accumulated after
each file as it gets overwritten by the other file getting loaded.
Perhaps a transaction is required?
The cron job at the end of the day calculates the quota correctly but
by then, the user has uploaded many times more than their quota
For example, we were getting numbers such as 244% of their 500MB
quota.
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