[rrd-users] new DS and the 1 month graph is still empty, nan to zero, how many hearbeats?

[ivan jr sy]

Hi all,

Its hard to keep my questions short, but ill try first to keep it simple. 

I have this kind of RRA:
rrdtool create cpu.rrd -s 60 \
         DS:CPUuse:GAUGE:120:0:U \
         RRA:AVERAGE:0.5:1:120 \
         RRA:AVERAGE:0.5:5:288 \
         RRA:AVERAGE:0.5:30:336 \
         RRA:AVERAGE:0.5:120:360 \
         RRA:AVERAGE:0.5:720:730

The system just got deployed (a few hours ago). When creating the "1 Year (12 hours average)", graph is still empty coz its not yet 12 hours... The date figures for current:, average: and max: are "nan".

Questions:
- is there a way that the image is still displayed, but an alternative text will be inserted explaining that "this graph is still empty coz the system has to wait for 12 hours" and the "current: max: average:" text are hidden/not displayed. I understand that I need to check when was the RRA first updated, and check if that is between now and 12 hours ago. I'm looking for samples and tips&trick that the mailing list can share.

- previously, I've asked a question regarding "u" and "m" when GRPINT "2.0lf%s". I now understand that "333m" means 0.3333333333333. But how do I (just literally in GPRINT) show it as "0.3" (one decimal)? Is there an alternative other than using the CDEF?

- How about if it's "123u"? (any tips for "u"?)

- I've read about 'Nan' converted to "0" using CDEF, but what are the pros? cons?... I was hoping that there is a way, without manipulating the data and just making it a literal display: '0'

(far off) 
- i got the basic idea of a 'heartbeat'... 
The sensor and my linux box are connected via rs232. now... the sensor is really unstable, there are times when it just missed sending data for 5 minutes.

Is there a way to determine, how many times the hartbeat resulted to unknown?, when was the last one? (for me to determine when the sensor paused), and is there a way to make an independent trigger? (if the heartbeat passes, call a script to re-check/resurrect the sensor).