[Dovecot] v2.0.alpha1 released

[Timo Sirainen]

On Oct 13, 2009, at 6:28 PM, Ed W wrote:

> Perhaps I misunderstand, but doesn't dovecot send a "keepalive" on  
> connections which are idling?

Yes, it's configurable nowadays:

   # How many seconds to wait between "OK Still here" notifications when
   # client is IDLEing.
   #imap_idle_notify_interval = 120

And I did think of that in my previous mail, but then thought it  
wasn't relevant because client was only receiving data, but now I  
realized that of course the client will also have to send back TCP ACK.

> I can imagine that in the case of a typical cell phone with say 3  
> email accounts, there will be likely three idle connections (or  
> more) to dovecot and each will end up sending keepalive packets at  
> slightly different intervals for each connection.  By synchronising  
> this network traffic you would potentially increase battery life by  
> up to a factor of 3 (ie turn on the radio to send the keepalive for  
> all connections in one go, rather than turning the radio on three  
> times as often)... (I think perhaps that's optimistic, but you can  
> see that quite large gains might be possible here)

Oh. That does sound like a good idea. Hmm. I think there's an easy way  
to implement this:

next_still_here_sending_timestamp = imap_idle_notify_interval -
   (time(NULL) + crc32(username)) % imap_idle_notify_interval;

The username CRC32 is there to avoid network/load spikes when all the  
processes try to send the "Still here" at the same time.