Comments about ntpviz
hmurray at megapathdsl.net
Tue Aug 23 20:38:54 UTC 2016
The part I forgot to mention is that if I was going to do something to make
my setup better, I would try to make a wrapper to drive gnuplot - a little
window off to the side so I could poke Next rather than typing return at the
gnuplot command window. The main thing I want is a way to backup a few
graphs. The second step would be a simple way to adjust vertical and/or
horizontal scaling (aka zoom in/out) to cover the cases where I didn't
anticipate I would want one and/or didn't get it right.
> So two graphs, one for today and yesterday? ntpviz can do that.
No, one graph, 48 hours wide, yesterday on the left and today on the right.
The part of today that hasn't happened yet (or hasn't been copied over to the
local system) is empty.
Remember, I'm using pre-edited gnuplot commands. There is no place in my
work flow to tell gnuplot how wide the graph should be.
I often set the graph to be 8 extra hours wide so the key has a place to go
without trashing part of the graph I might be interested in.
[Need two different scales.]
>> set yscale [xx:xx]; replot
>> pause -1
> Yeah, I do see that is handy now and then.
It happens enough for me that I did something about it.
> Looks like a holiday tree, I find it hard to ficus on the red/green pairs.
The usual nasty case is boundaries between between red/blue areas. Your eye
has lots of chromatic aberration. It can't focus on different colors at the
same time. Red and blue are the farthest apart.
[using crappy colors]
> Yeah, if you have any specificc suggestions on how ntpviz can fix that. But
> please no red/green barber polls...
The only fix I know about is to manually pick the set of colors you are
willing to use and then tell gnuplot which color to use for each chunk of
data. If you let it assign things automatically, it will rotate through all
of them and that includes the crappy ones. Yellow is 5 so you get 4 decent
ones without any effort. Somewhere around 4 different data sets many graphs
get too busy so this is only a problem occasionally. I have one plot where
lots of lines work well. It's the temperature for various machines and
places in the room. They don't overlap much all track well so you can see
any interesting differences.
> Yeah, a down server is ugly. It should be shown ugly.
I have some systems that are normally off to save power. For me, the gap is
enough to attract my attention.
I had one setup where the script to start ntpd appended 2 blank lines to all
the stats files. gnuplot treats that as a request to not draw the line
connecting the points on either side.
> Yup, I'm working on autoscaling. A lot more to do. I'm thinking of just
> clipping the outliers ( < 0.5%, > 99.5% ) with a text message of the worst
I want to be able to see the outliers. At least optionally default on.
I think you will have troubles trying to automate that. It will get mixed up
>> If you have a busy server, there is interesting stuff in usestats.
> Such as?
The reason I added it was to get the memory usage.
sysstats has packet counts. I think usestats has wakeup counts so you should
be able to figure out how many packets arrived while you were already working
There is lots of room for improvement in this area. I thin it's all on the
[rawstats/round trip time]
> An interessting idea, but NTPsec needs to focus on core ntpd needs until
> those are nailed down.
The round trip time is important if you are trying to understand what
happened to a server out on the big bad internet. It's probably less
interesting for debugging your local LAN. It might be helpful if you are
A reasonably common quirk is that the offset of a server will jump, say 10
ms. If the round trip time jumps at the same time, the problem is most
likely a routing shift rather than a glitch at the remote server.
> Yeah, been looking at that. Since ntpd is undersampling the PPS it can be
> either good, or real bad. I'm tempted to get Eric to fix the bug first, but
> maybe I'll need to data so he sees the bug first.
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