Recent (probably MacOS) mail app provoking endless cyrus.index writes on 2.3 server.

[ktm at rice.edu]

On Tue, Oct 13, 2015 at 11:13:43AM +0200, Eric Luyten wrote:
> Howdy,
> 
> 
> In recent weeks I have noticed a number of clients entering seemingly
> endless loops writing the cyrus.index on a sometimes empty mailbox,
> resulting in several dozen MB/s writing to our mail spool for hours on
> end.
> 
> Always IMAP, never POP, sometimes TCP/143, mostly TCP/995
> 
> I enabled telemetry logging on several of these accounts and here's a
> typical snippet :
> 
> <1444726821<1<1444726821<804.3507 IDLE
> >1444726821>+ idling
> <1444726821<D<1444726821<ONE
> >1444726821>1804.3507 OK Completed
> <1444726821<1<1444726821<805.3507 EXPUNGE
> >1444726821>* 0 EXISTS
> * 0 RECENT
> 1805.3507 OK Completed
> <1444726821<1<1444726821<806.3507 IDLE
> >1444726821>+ idling
> <1444726821<D<1444726821<ONE
> >1444726821>1806.3507 OK Completed
> <1444726821<1<1444726821<807.3507 EXPUNGE
> >1444726822>* 0 EXISTS
> * 0 RECENT
> 1807.3507 OK Completed
> <1444726822<1<1444726822<808.3507 IDLE
> >1444726822>+ idling
> <1444726822<D<1444726822<ONE
> >1444726822>1808.3507 OK Completed
> <1444726822<1<1444726822<809.3507 EXPUNGE
> >1444726918>* 0 EXISTS
> * 0 RECENT
> 1809.3507 OK Completed
> 
> 
> 
> Clues ?
> 
> 
> Eric Luyten, Computing Centre VUB/ULB.
> 

Hi Eric,

The El Capitan Mac Mail was recently released. It definitely has a problem.
We saw our typical sync log size go from 10k when busy to 100k+. We are going
to recommend that people wait to upgrade to that release until the problem is
addressed.

Regards,
Ken