I have created RRD DB, which should receive update every hour and display values of received orders for last 24 hours:
rrdtool create db.rrd --step 3600 --start 1381230000 DS:measurment:GAUGE:4800:0:U RRA:AVERAGE:0.5:1:24
Everything is working OK, except fact when I miss one value in update two of them are missing from database:
So let say i have:
....
1381240800:1203
1381244400:1302
1381248000:1132
1381251600:988
....
But if the second update wouldn't be received (1381244400:1302), the third (1381248000:1132) will be missing dispite fact that it arrived.
Can someone tell me why is this happening?
The problem is that if the previous update is missed, the interval between the last and the current update is larger than the 4800 seconds you specified in your DS definition. Therefore rrdtool will treat all data between the last and the current update as UNKNOWN.
In rrdtool 1.4.8 I have introduced a special case for GAUGE DS updates where the previous update is more than MRHB in the past. In this case rrdtool will now treat the data supplied as valid from now-MRHB until now.