Should programs handle system time jumps?

From: Ulrich Eckhardt (doomster_at_knuut.de)
Date: 08/30/04 

Date: Mon, 30 Aug 2004 12:45:58 +0200

Hi!
I'm in an argument with a coworker about whether a program must gracefully
handle jumps in the system time. The jumps occur when, for demonstrating
logfile cleanup, people set the time a year ahead or back. This
test-procedure is part of a validation, so not really easy to change.

The problem is that certain threads that poll things wait between polls for
e.g. a second. If, in that waitcycle, the systemtime is rewound by a year,
it will wait virtually forever.

My point of view is that this is not a normal working condition and it is
perfectly valid to require a reboot for the clock change. Related to that,
can anyone give examples for programs that are either designed to handle
this gracefully or known no fail under such circumstances? Im particularly
interested in typical services running on MS Windows >= NT 5.0 and Debian
GNU/Linux, both configured to be rather 'embeddish'.

I know that NTP clients are written so that they don't create jumps in
systemtime. They rather accelerate or slow down the systemtime until it
reaches the target setting.

thank your for any pointer

Uli

Relevant Pages

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