[Dovecot] Time moved backwards

[Bill Cole]

At 11:31 AM +0400 5/13/08, Eugene wrote:
>Hi Timo,
>
>From: "Timo Sirainen" <tss at iki.fi>
>>>I suggest that Dovecot simply terminate the current connections (causing the
>>>client to reconnect) or -- if the time change is really that much of a
>>>problem -- to restart itself automatically.
>
>>I guess terminating all current connections and restarting all processes
>>would be pretty safe, but it's not really a high priority change for
>>me..
>
>Nevertheless, it would be very nice if you could fix it. It's a 
>fairly big availability problem (for us, at least).

Then you have a badly broken system. There is no explanation for time 
going backwards on a server on a frequent unplanned basis that is not 
reducible to administrative incompetence or malfunctioning hardware 
(and the latter as a chronic issue can be seen as just a special case 
of the former.)

>And after all, if we are terminating already, adding a simple spawn 
>call before that should not take much time?

A system clock that moves backwards is indicative of a problem. 
Having a service respawn itself as a response to a problem that is 
outside of its control (i.e. the respawn is not itself a fix) is 
begging for trouble, because that behavior has to be carefully 
controlled to prevent it from contributing to a cascading problem. On 
a system whose clock is untrustworthy, this is a significant 
challenge. The effort to do that sort of code correctly just to 
accommodate
people with broken systems seems like a terrible waste.


On the other hand, writing a freestanding watchdog for a critical 
service is (or at least should be) something any good sysadmin can 
do. If you are stuck with hardware so broken that it jumps backwards 
in time without warning but not so broken that you can get it 
replaced, and it lives in a network or resource environment that 
prevents you from fixing the core problem, you can adapt to the 
breakage yourself.


-- 
Bill Cole                                  
bill at scconsult.com