Joel,
At the very real risk of boring everybody on this list to tears, I have
a burning agenda to expose this issue to a responsible community.
Your flight dispatcher machines are running just fine and one of them
suddenly veers off course by one hour. Your application is airt traffic
control. Your choices are:
1. Immediately shut down the timewarper and dispatch a repair crew.
2. Force the timewarper to slew, even though it will take a week to slew
within one second, your sanity limit. During most of the week the warper
clock will be ahead of the rest by more than the sanity limit. Of
course, a rew airplanes might collide, but will crash in monotonic order.
3. Step the clock back, possibly confusing flight planning, but at least
all planning is to the same clock and nobody crashes.
Comments from your database gurus, ALPA and PATCO would be highly prized.
Dave
Joel Shellman wrote:
--- "David L. Mills" <[EMAIL PROTECTED]> wrote:
The only thing the -x option does is change the step
threshold to 600 s,
or ten minutes. I find it mighty curious that you
would consider a large
discrepancy like that within acceptable bounds for a
any consistent
distributed data system, but that's not my call.
I plan to run ntpd -q -g upon system startup, so that
discrepancy "should" never happen. However, the most
important requirement is to have a sequential clock so
that timestamps on audit logs are sequential. Also,
this is in an isolated environment--probably won't be
using public servers.
Note that the tinkers disable all steps for any
reason, including a step
at startup. If you need that, you will need another
program or to start
ntpd in ntpdate mode before launching the daemon.
Right, which we're planning on doing anyway.
You made me think though. It sounds like what we
really want is:
tinker panic 5 # or some appropriately small number
tinker step 0
After running ntpd -q -g on system startup, we should
have the same clock. So long as the clocks aren't so
incredibly off as to lose or gain 5 seconds, we should
stay within 5 seconds and never clock step. And if we
get 5 seconds off, ntpd dies, alarms go off and
someone manually figures out why the clocks aren't
able to stay within 5 seconds of each other.
Thank you very much for your help.
-joel
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