[Dovecot] Feeature requests (server failure handeling)

[Timo Sirainen]

On Mon, 2005-04-25 at 07:22 +0100, Andrew Hutchings wrote:
> Suggested features (after we had a nasty NFS disk failure):
> 1. Have reject connections after load of X (like exim, sendmail, etc...), when 
> the NFS started to fail it took a long time to access the mailboxes, average 
> load on the dovecot servers was 30-40 (until the NFS turned the disk r/o and 
> all connections were getting kicked out).

I think this should be a separate script which just notifies Dovecot to
stop handling connections.

> 2. Have a dead server response setup.  Freeserve/Wanadoo do this by setting a 
> flag in their software which accepts all POP connections regards of user/pass 
> and says there is no mail (users don't panic and flood the phones for a while 
> then).  Not sure how you would do this with IMAP though.

Someone already mentioned the possibility of using -ERR (and IMAP can do
it with "NO [ALERT]") which would show the error message to client. This
could be useful I guess..

But how should this be configured? And should it happen only after
successful login or should all login attempts be just failed with the
error message?

Actually it's already possible I think.. If passdb returns:

nologin=yes
reason=Sorry, server down

It won't let anyone log in and gives the error message as the reason.
Although that doesn't set IMAP's [ALERT] tag.. Maybe another flag should
be set for that.

So .. then what's needed is a way to make passdb return those settings.
With SQL it's possible by changing Dovecot to use some alternate
dovecot-sql-down.conf file and sending HUP to dovecot. Not exactly easy
I guess..

Maybe some auth_failure_file-setting which points to a file. If the file
exists, it overrides normal passdb handling and returns whatever
settings that are set in it to clients?

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