mahara-contributors team mailing list archive

[Aaron Wells <1606749@xxxxxxxxxxxxxxxxxx>]

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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