[Dovecot] dovecot backend on director ?
Hello Timo,
The last time I checked my understanding about director was that :
- backend/"real" imap servers should not be on the same host (or the same dovecot instance) to avoid proxying loops.
Is it still the case with the latest 2.1 stable release ? Is there a plan to be able to run director and real server on the same host, thus requiring only 2 hosts instead of 4 to have load balancing and a redundant director ?
- director itself was not able or meant to check if one of the real server was down (some script was pointed long time ago in this list).
Same questions.
- you'll have to use dovecot lmtp instead of let's say procmail. Would deliver be still a choice or is lmtp the only deliver compatible choice ?
In what case would lmtp be more useful than deliver ? To have some sort of "remote LDA" ?
By the way, what gets indexed on deposit on the mailbox since, by definition, the user has not done any request yet ?
Thanks.
-- Thomas Hummel | Institut Pasteur <hummel@pasteur.fr> | Groupe Exploitation et Infrastructure
On 4.12.2012, at 19.33, Thomas Hummel wrote:
Hello Timo,
The last time I checked my understanding about director was that :
- backend/"real" imap servers should not be on the same host (or the same dovecot instance) to avoid proxying loops.
Is it still the case with the latest 2.1 stable release ? Is there a plan to be able to run director and real server on the same host, thus requiring only 2 hosts instead of 4 to have load balancing and a redundant director ?
Either:
a) Run two Dovecot instances with different base_dirs and different TCP ports. This has been used by several installations.
b) One Dovecot instance with proxy_maybe. I'm not completely sure if this works. I think it does.
- director itself was not able or meant to check if one of the real server was down (some script was pointed long time ago in this list).
Same questions.
This probably not happening anytime soon. It's not always obvious if a backend server is down or just heavily loaded. Better to use an external script that can be tweaked.
- you'll have to use dovecot lmtp instead of let's say procmail. Would deliver be still a choice or is lmtp the only deliver compatible choice ?
In what case would lmtp be more useful than deliver ? To have some sort of "remote LDA" ?
With LMTP the mailbox access is done by the proper server. With LDA it's always done by the server that runs the LDA, again causing all the troubles that director is supposed to prevent. I've had some thoughts about changing dovecot-lda to be LMTP client by default, but that hasn't happened yet. It wouldn't be difficult to write a separate LMTP client binary (and there probably already are those).
By the way, what gets indexed on deposit on the mailbox since, by definition, the user has not done any request yet ?
Dovecot's caching decisions are remembered. So it adds those headers/etc that the user's current client(s) are interested in. http://wiki2.dovecot.org/Design/Indexes/Cache has some details about the cache decisions.
On Tue, Dec 04, 2012 at 07:44:32PM +0200, Timo Sirainen wrote:
b) One Dovecot instance with proxy_maybe. I'm not completely sure if this works. I think it does.
I remember an old thread were someone (you?) said proxy_maybe was not ready (yet?) for director, causing "Proxying loops".
Better choose the multiple instance solution then I guess.
With LMTP the mailbox access is done by the proper server.
What do you mean by the proper server ?
I don't want LMTP to be a SPOF, so I guess that if I've got for instance 2 directors, 2 real servers and mailboxes on NFS, I'd want 2 LMTP servers :
on which servers should those LMTP servers run ? On the director servers (which would mean director should have the mailboxes mounted) ?
Thanks.
-- Thomas Hummel | Institut Pasteur <hummel@pasteur.fr> | Groupe Exploitation et Infrastructure
participants (2)
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Thomas Hummel
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Timo Sirainen