[rrd-users] 1-day step interval woes

Zac DeLesDernier zac+rrdtool at wozzle.com
Mon Aug 28 17:30:57 MEST 2006

So a few months ago, I threw together a quick script to help our 
intranet users track their weight.  It mostly works as expected, though 
there are a few minor annoyances that I hope you guys can help with.  
First, consider the following:
* Data points are entered manually, once a day, usually in the morning.

* The RRD files are created like so: RRDs::create("$user.rrd", '-s', 
86200, 'DS:ds0:GAUGE:345600:0:300', 'RRA:AVERAGE:0.5:1:56', 
'RRA:AVERAGE:0.5:7:52', 'RRA:AVERAGE:0.5:28:48');
    - the "step interval" is 86200 seconds = 1 day
    - there is only 1 DS in the rra, which will be considered UNKNOWN 
after 4 days
    - there are 3 RRAs: 56 1-day samples, 52 1-week samples, 48 
1-month-ish samples

So... now for the annoyances...

* Users expect the data point that they've just entered to show up on 
the graph.  Sometimes... this doesn't happen.  Like when you first 
start... (or, more generally, whenever yesterday's value is UNKNOWN.)

* Users expect today's data point to show up *where it should*, 
numerically.  This often doesn't happen.  I'm sure this is because the 
data doesn't appear on the graph until it's passed through a 
consolidation function, but... with a RRA with single PDP datapoints, 
wouldn't that pretty much be the same?

* It would be nice if the lines representing the daily data points lined 
up with the graph lines... but they're offset by the time zone.

* It would be nice if weeks fit into the week lines on the graph.  Right 
now... Tuesday appears to be day 1...?

I've attempted to resolve some of these issues by *adding the local time 
zone offset* when a user enters in their daily data point.  In the 
morning, this seems to work ok... visually.  But if a user enters their 
weight in the evening... "tomorrow's" line shows up, too.  Help!


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