[Dovecot] Dovecot IDLE bandwidth usage

[Timo Sirainen]

On Thu, 2007-08-16 at 02:22 +0200, Fredrik Tolf wrote:
> I just recently discovered the IMAP IDLE command and tried it out with
> my Dovecot server. It seems to work fine and all, but it seems to be
> using quite a deal of bandwidth, because of the "* OK Still here"
> messages sent by the server at two minute intervals. I would argue that
> is a bit of a problem when using the IDLE command for "Push mail" on a
> mobile phone.

The point is mostly to keep connections alive when NATs and stateful
firewalls are used.

> Are those messages really necessary? I mean, Dovecot still times out
> after half an hour if the client doesn't "finish" the IDLE command and
> re-issues it, right? (Coincidentally, I would like to argue that it
> would be better not to time out at all during an IDLE command 

I've actually changed it like that for v1.1. I'm not sure if I should
change it for v1.0.

> and just
> turn on TCP keepalives instead, but that is the minor issue here)

TCP keepalives get sent so rarely that they don't keep NATed connections
alive. (Linux's tcp(7) says the first one is sent after 2h of idling)

> I'll apologize in advance if this is already a tunable option, but I
> haven't found anything about it in the configuration file.

Perhaps there should be.. But since this is client connection-specific
and not server-specific issue I'm not sure if that's a good idea either.
Wonder if this could be figured out automatically in some way..
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