MESSAGE quota resource implemention
julien.coloos at atos.net
Wed Aug 31 11:50:36 EDT 2011
As discussed on IRC last week, I worked on implementing MESSAGE quota
resource in cyrus (see RFC 2087; STORAGE resource already being handled).
I created a branch based on Greg's 'annotate' one on github, since his
work on annotation storage management made mine a lot easier.
Details on the changes I made:
- added MESSAGE quota resource management
-> updated cunit test
-> added 'quotawarnmsg' option which behaviour is similar to
'quotawarnkb'; warning message shown when selecting folder in IMAP tells
which resource limit was triggered
-> added 'autocreatequotamsg' option, to set MESSAGE limit
(unlimited by default) when user auto-creates its mailbox
- xfer transfers all non-unlimited resources
- added helper function to compute annotation storage usage for a
- changed the way quota entries are read/written
-> resources presence in fetched entry is remembered
-> when writing entry, only present resources are written
-> when setting resources limits, entries which were not present
upon fetching are now marked as present and their current usage is computed
- quota utility lists and computes (-f) all resources associated to
The branch 'quotamessage/gnb/annotate' is available here:
git://github.com/worldline-messaging/cyrus-imapd.git. It is based on
Greg's 'annotate' branch on github.
- added tests for MESSAGE resource
- modified current tests to play a bit with subfolders and setting
quota after adding messages/annotations
- special test to check new resource usage is computed when necessary
for pre-existing mailboxes (which only have usage for STORAGE resource)
The branch 'quotamessage/gnb/master' is available here:
git://github.com/worldline-messaging/cassandane.git. It is based on
Greg's 'master' branch on github.
Things that may be worth noting:
- DUMP/UNDUMP currently does nothing special about MESSAGE or
X-ANNOTATION-STORAGE quota resources
-> should it be transferred ?
-> without breaking backward compatibility, limits could only be
transferred through a 'fake' file entry, as for annotations
- quota usage is currently stored in a uquota_t variable, and delta
is computed as quota_t; so theorically there could be overflow issues if
quota usage to add/substract cannot be held in a quota_t; in practice it
should be unlikely since that would mean a usage of over 2^63-1
Why the change concerning quota entries read/write ?
The thing is that I wanted to make version upgrading as painless as
possible, both for users and in the code.
With previous code, when quota entry exists and is read, missing
resources are initialised with default values (0 usage, unlimited). Thus
only usage delta is tracked, and actual usage computing would only
happen if quota entry was missing: this is not nice when upgrading,
since lots of mailboxes are likely to have an entry with only the
STORAGE resource present.
So actual usage has to be computed at some point for newly handled
resources. The idea here is to compute it when setting the resource for
the first time. To do that it was necessary to know when the resource
was not previously present and keep it that way until its limit is
finally set for the first time.
This scheme has another advantage: for platforms where only STORAGE
quota is used, quota entries size remains as it is now. Only people
using those new quota resources will have their quota entries grow to
store the new data.
Comments are welcomed :)
I think that there are two things that may also be done concerning quota
- always recompute resource usage when changing its limit from
unlimited to bounded
-> currently it is only done once when setting the usage limit for
the first time
-> that way, it may not be necessary to track resource presence
when reading/writing quota entries
-> but maybe it could be too time consuming in some cases, since it
seems to be possible to associate a quota resource to a whole domain
(recomputing usage for all mailboxes would then take some time)
- do not write resource in quota entry when its usage is unlimited
-> except for the STORAGE resource, for backward compatibility
-> would also help keeping quota entries size to the bare minimum
What do you think ?
PS: should I open a new bugzilla ticket for that ?
cunit: on my computer cunit tests succeed except the 'foreach' one in
the 'quota' suite which timeouts (it seems messing with 4096 quotalegacy
is too much for my computer).
cassandane: a few quota tests I added fail due to some of the issues I
reported (#5327 and #5329). And poor lemmings (well thought out name in
this context :)) are dying hopelessly and endlessly in the
Cassandane::Cyrus::Master test, preventing it to complete. Don't know if
it is normal.
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