[rrd-users] How to find a grafics error?

[Peter A. Menzel]

Hello,

my cgi output for the monthly periode seems to have errors (in detail: see attached image).
As you can see on http://hk1.famenzel.at/cgi/hk1.cgi the output for the last week ("letzte Woche") is ok (continued graphs for the temperatures), but shown interrupted in the monthly graph ("letzter Monat").
Also the pump indicators ("HK1Pumpe", "HK3Pumpe" aso) show some activity in this graph and the yearly one ("letztes Jahr"). This seems to be wrong too.

How can I find the source of the problem?

Thank you and BR
Peter

[Simon Hobson]

Post by Peter A. Menzel
my cgi output for the monthly periode seems to have errors (in detail: see attached image).
As you can see on http://hk1.famenzel.at/cgi/hk1.cgi the output for the last week ("letzte Woche") is ok (continued graphs for the temperatures), but shown interrupted in the monthly graph ("letzter Monat").
Also the pump indicators ("HK1Pumpe", "HK3Pumpe" aso) show some activity in this graph and the yearly one ("letztes Jahr"). This seems to be wrong too.
How can I find the source of the problem?

You'll need to provide a lot more information - at the moment it's "I create a graph using an unknown script/command, using unknown data, and 'it doesn't work'".

A first step would be to show what commands you used to create the RRD files and the graphs, plus a sample of the data going in.

Your graph in the email (the link doesn't work for me) has breaks in it - that can often be as simple as having a heartbeat interval that's too short so you get a lot of "unknown" data.

[David Thornton]

I would also like to point out that if you have a couple of unknowns in the
hi res data they might not be noticeable at high res, but as you aggregate
data a single unknown value in a group of aggregated values will make the
aggregate value "unknown" making it more noticeable. unknowns propagate ,
taking out larger and large data points ( This is also true for cdefs . ) .


David

Post by Peter A. Menzel
Hello,
my cgi output for the monthly periode seems to have errors (in detail: see
attached image).
As you can see on http://hk1.famenzel.at/cgi/hk1.cgi the output for the
last week ("letzte Woche") is ok (continued graphs for the temperatures),
but shown interrupted in the monthly graph ("letzter Monat").
Also the pump indicators ("HK1Pumpe", "HK3Pumpe" aso) show some activity
in this graph and the yearly one ("letztes Jahr"). This seems to be wrong
too.
How can I find the source of the problem?
Thank you and BR
Peter
_______________________________________________
rrd-users mailing list
https://lists.oetiker.ch/cgi-bin/listinfo/rrd-users

[Simon Hobson]

rrdtool create AgroFire.rrd --step 1 \
DS:KesselTemp:GAUGE:2:U:U \
...
RRA:AVERAGE:0.5:1:864000 \

Can you be certain that you provide an update *every* second ?

heartbeat defines the maximum number of seconds that may pass between two updates of this data source before the value of the data source is assumed to be *UNKNOWN*.

Eg, if you miss an update at time t=1 having done one at time t=0, does the value become unknown at time t=2 or *after* time t=2. The difference is that if you miss just one update, then in the former condition, when you come to do the update at time t=2, the data from time t=0 to time t=2 will be marked as unknown; but if it's the latter then the data wouldn't become unknown unless you also miss an update at time t=2.

So firstly I would be checking to see that you are reliably doing an update every second and not creating a few unknown values. You might consider increasing the heartbeat value.

You have specified an xff value of 0.5, so you would regard a consolidation as unknown if 50% of the source values are unknown. Since missing one update could be marking 2 seconds worth (ie 2 primary steps) as unknown, then missing an average of one update every 4 seconds would result in missing consolidated data.

[Peter A. Menzel]

Hi Simon and David,
thank you for your hints!
I actually found some missing update values - that means not every second a new set of values.

Now I intent to tune the heartbeat value to 5 instead of 2,
and step size of 1 remaining constant...
So missing 1, 2 or 3 measures will not generate an *unknown* value in the RRD.

Do you think that is the right way?

Thank you and BR
Peter
 

Post by Simon Hobson

rrdtool create AgroFire.rrd --step 1 \
DS:KesselTemp:GAUGE:2:U:U \
...
RRA:AVERAGE:0.5:1:864000 \

Can you be certain that you provide an update *every* second ?
You have a step size of 1, and a heartbeat value of 2. That means that
you can only have data 2 seconds old before it is considered unknown.
What isn't clear is which side of the point the decision is taken as
the manual says : > heartbeat defines the maximum number of seconds
that may pass between

two updates of this data source before the value of the data source is
assumed to be *UNKNOWN*.

Eg, if you miss an update at time t=1 having done one at time t=0, does
the value become unknown at time t=2 or *after* time t=2. The difference
is that if you miss just one update, then in the former condition, when
you come to do the update at time t=2, the data from time t=0 to time
t=2 will be marked as unknown; but if it's the latter then the data
wouldn't become unknown unless you also miss an update at time t=2.
So firstly I would be checking to see that you are reliably doing an
update every second and not creating a few unknown values. You might
consider increasing the heartbeat value.
You have specified an xff value of 0.5, so you would regard a
consolidation as unknown if 50% of the source values are unknown. Since
missing one update could be marking 2 seconds worth (ie 2 primary steps)
as unknown, then missing an average of one update every 4 seconds would
result in missing consolidated data.
_______________________________________________
rrd-users mailing list
https://lists.oetiker.ch/cgi-bin/listinfo/rrd-users
 

[Simon Hobson]

Post by Peter A. Menzel
I actually found some missing update values - that means not every second a new set of values.
Now I intent to tune the heartbeat value to 5 instead of 2,
and step size of 1 remain constant...
So missing 1, 2 or 3 measures will not generate an *unknown* value in the RRD.
Do you think that is the right way?

It's probably the right thing to do and my guess is that it will "cure" your gaps - but really it's your data, you have to decide whether it's right for your needs. Some people want to see the unknowns, others want to "ride over" them.