[Xymon] "ports" RRD graph is often flaky.

[Shawn Heisey]

I see several graphs like this in xymon (4.3.23), where at least one of
the port graphs (configured in analysis.cfg) has lots of data points
missing:

https://www.dropbox.com/s/l483lilzh5n610k/flaky-xymon-port-graph.png?dl=0

Any idea how I can fix this?  As you can see, the red line for http has
data for the entire graph, while the blue line for ajp is very spotty.
I just added the last two monitors less than an hour ago, so I don't
have history on those yet.

This is not unique to this host.  As far as I can tell, the port
listings coming back from the client are always good, even when the
graph has no line.

Thanks,
Shawn