[rrd-users] Bar graph by hour, day, month

Alex van den Bogaerdt alex at vandenbogaerdt.nl
Tue Sep 30 00:17:20 CEST 2014

----- Original Message ----- 
From: <bsuarez at free.fr>
To: "Simon Hobson" <linux at thehobsons.co.uk>
Cc: <rrd-users at lists.oetiker.ch>
Sent: Monday, September 29, 2014 4:07 PM
Subject: Re: [rrd-users] Bar graph by hour, day, month

> Hi,
> My water meter delivers one pulse per liter consumed. I have a script that 
> counts the pulses (raspberry and piface).
> Periodically I want to store in the RRD database  the number of pulses.
> The first solution is to periodically store the number of impusions since 
> the last backup.
> The second solution is to periodically store the total impusions since the 
> start of counting

There may be another solution:
Don't store and count. Just feed to RRDtool as soon as a pulse comes in. 
Your counter type would still be ABSOLUTE, you would feed number 1 (1 
liter). No need to remember anything, except that it would be wise to create 
an idle timer.  If no pulses are generated for 24 hours (or any other 
suitable number), then feed number 0 to RRDtool and reset the idle timer. 
(and, of course, don't forget to set the timeout value in your database to 
an appropriate value, larger than 24 hours or the number you chose).

> For graphs, displaying data on last 5 minutes, last hour, last day, last 
> month should be enough.

What Simon tried to explain to you, is that "last month" is tricky. You 
probably expect to get columns for each day. If you are aware how RRDtool 
works (by design) and if you do not mind seeing days which start at midnight 
UTC, then no problem.

More information about the rrd-users mailing list