[Dovecot] Re : [Plugin dev] First-time-only cache lock failure

[John G]

Thanks a lot for the clarifications.
I'm now using an extension to store my uint32_t UID and it works properly.


>________________________________
> De : Timo Sirainen <tss at iki.fi>
>À : John G <john_g14 at ymail.com>; Dovecot Mailing List <dovecot at dovecot.org> 
>Envoyé le : Lundi 14 mai 2012 18h45
>Objet : Re: [Dovecot] [Plugin dev] First-time-only cache lock failure
> 
>On Mon, 2012-05-14 at 17:17 +0100, John G wrote:
>> Hi
>> 
>> This is a question related to plugin developement on Dovecot 2.1.4.
>> 
>> I'm currently implementing a dovecot plugin that retrieves mails from a corporate server through an internal protocol.
>> The plugin is very similar to the pop3c storage (lib-storage/index/pop3c).
>> The plugin has to map original server UIDs to IMAP UIDs, using MAIL_CACHE_POP3_UIDL cache field the same way pop3c does.
>> 
>> So, I've got a function similar to pop3c_sync_messages(), performing several mail_index_append() and mail_cache_add() calls.
>> 
>> The problem is that on the first sync, when the index and cache files don't exist yet, there's a failure writing data in cache.
>> The call to mail_index_sync_commit()\mail_cache_transaction_commit() fails because of mail_cache_transaction_lock().
>> 
>> The index and cache files are properly created, but the cache doesn't contain the MAIL_CACHE_POP3_UIDL values.
>> It works properly on the second sync, the MAIL_CACHE_POP3_UIDL field being properly saved.
>> 
>> Would you have some ideas on what could be wrong here?
>
>I'm not entirely sure what the problem is with cache file, but you
>shouldn't use cache file anyway for this purpose if you want it to work
>reliably. Cache file's contents can disappear in some situations. pop3c
>shouldn't do it either, but it doesn't have to be very reliable :)
>
>If the original server UIDs are of fixed length (or have a reasonable
>maximum length), add the UIDs to dovecot.index file itself by
>registering an "extension". For example see how mdbox's "mdbox"
>extension that creates struct mdbox_mail_index_record for each mail.
>
>If the original server UIDs are variable length, you can create a
>separate mapping file similar to Maildir's dovecot-uidlist.
>
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