[Dovecot] Corrupted transaction log file

[Peter Mogensen]

On 2011-11-04 22:26, Timo Sirainen wrote:
>> Nov  4 15:10:42 mail dovecot: imap (test at aaaone.net): Error: Corrupted
>> transaction log file /mail/3340444/.TestMails/dovecot.index.log seq 2:
>> indexid changed 1320419300 ->  1320419441 (sync_offset=0)
>
> Session A had TestMails open and created with index file whose ID was
> 1320419300 (that's also UNIX timestamp of its creation time, Fri Nov  4
> 17:08:20 EET 2011).
>
> Session B came and recreated the index files 141 seconds later with ID
> 1320419441. Either it didn't see A's original index files for some
> reason or it simply decided to recreate them for some reason. Either way
> this shouldn't have happened.

Turns out this is expected to confuse Session A.
The client in question sometimes start the session (B) with this command 
sequence:
DELETE folder
CREATE folder
APPEND...

Any Session A having opened "folder" of course would be surprised that 
there's a new index file (makes we wish for an IMAP5 where 
folderID!=displayname)

This can be reproduced by hand speaking IMAP with two telnets.

Only question left is, why does Dovecot end the log sequence by saying:

"Disconnected: IMAP session state is inconsistent, please relogin."

  ... when it is capable of detecting this and returning "BYE folder 
deleted under us" and logging the same.

/Peter