dovecot - May 2015 - race condition? -> Error: dict quota: Quota update failed, it's now desynced

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I get this error now and then, but only for users, that share or use 
shared mailboxes.

See this snippet:

2015-05-22 02:27:09 IMAP(<uid1>) [28776]: Info: Disconnected: Logged out
in=21450 out=76933
2015-05-22 02:27:09 IMAP(<uid1>) [28774]: Info: Disconnected: Logged out
in=3769 out=16379
2015-05-22 02:27:09 IMAP(<uid1>) [28770]: Info: Disconnected: Logged out
in=641 out=394985
2015-05-22 02:27:09 IMAP(<uid1>) [28614]: Info: Disconnected: Logged out
in=510 out=2178
2015-05-22 02:27:09 IMAP(<uid1>) [28768]: Info: expunge:
box=users.<OTHER-UID>.INBOX, uid=8711,
msgid=<008801d093ef$f46c00d0$dd440270$@example.com>, size=17433,
vsize=17849, from=[cut]
2015-05-22 02:27:09 IMAP(<OTHER-UID>) [28830]: Info: Disconnected: Logged
out in=555 out=2763
2015-05-22 02:27:09 IMAP(<uid1>) [28768]: Info: Disconnected: Logged out
in=628 out=2851717
2015-05-22 02:27:09 IMAP(<uid1>) [28768]: Error: dict quota: Quota update
failed, it's now desynced
2015-05-22 02:27:09 IMAP(<OTHER-UID>) [28827]: Info: Disconnected: Logged
out in=267 out=1256
2015-05-22 02:27:09 IMAP(<OTHER-UID>) [28824]: Info: Disconnected: Logged
out in=175 out=1073
2015-05-22 02:27:09 IMAP(<OTHER-UID>) [28831]: Info: Connection closed
in=550 out=3197
2015-05-22 02:27:09 IMAP(<OTHER-UID>) [28663]: Info: expunge: box=INBOX,
uid=8711, msgid=<008801d093ef$f46c00d0$dd440270$@example.com>, size=17433,
vsize=17849, from=[cut]
2015-05-22 02:27:09 IMAP(<OTHER-UID>) [28663]: Info: Disconnected: Logged
out in=800 out=25925

OTHER-UID shares the INBOX to uid1. Now, the _same_ message is about to 
delete once via the "sharing" uid and once from the consumer at the
same
time.

My quota backend is Postgres, via
quota = pgsql:/usr/local/dovecot-2.2.15/etc/dovecot/dovecot-dict-sql.conf.ext
  on Dovecot v2.2 hg 18272:466596200825 . I tried to replicate the error, 
by setting up two accounts, A shares INBOX to B, setup A and B in the same 
Thunderbird, configured that both A and B expunge the INBOX on termination 
of MUA, but I cannot reproduce that the same message is deleted twice in
parallel.

I also tried current hg's tip 8737:8906101589f9, but I cannot reproduce 
the error, no matter what I try.

Also, I think, that in this very case the quota is OK still, because it 
had been updated for the sharing user OTHER-UID.

- -- 
Steffen Kaiser
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