Why is Cacti showing an empty graph, even though the rrd file is created?
I have developed my own SNMP service, and i want to plot a graph of an OID provided. So, i have created a graph in Cacti. -) It is showing device up. -) It is creating rrd file. (RRDTool says OK). -) Showing the graph, but it's empty.
But when I check it, say
rrdtool fetch <rrd file> AVERAGE
it shows me nan for all the values. The monitored OID has value 47 and i have set min=0 and max=100.
I am using Cacti appliance by rpath:
http://www.rpath.org/ui/#/appliances?id=http://www.rpath.org/api/products/cacti-appliance
Still, I can't show value on graph..
Where is the problem? Can anyone please tell me?
Answer
First of all, use Cacti's "Rebuild Poller Cache" function under the Utilities menu. If that didn't work ,check if the RRD file is actually updating with new data. To do this use the command:
rrdtool last [filename.rrd]
This will output the last time (in unix timestamp) that a new value has been inserted into the RRA file which you can compare to the current time that date +%s will output.
If it's not updating with data then you should change the cacti log level to DEBUG via the settings page on Cacti's web UI and look for appropriate messages. If the poller couldn't get the data then it's usually an issue relating to connectiviy/SNMP. You can further check issues as such by manually polling the specific OID on that host:
snmpwalk -c[SNMP COMMUNITY] -v2c [HOSTNAME OR IP ADDRESS] 1.3.6.1.2.1
You can use the above command and OID (1.3.6.1.2.1) just to see if you're getting a reply. If that worked then you should change the command from snmpwalk to snmpget and the OID to the actual OID you're trying to poll and retry.
If the RRD is updating with new data but you're still getting NaN in your graphs then I suggest looking into the heartbeat and step values of the data source (via the data template) in relation to your polling interval and poller cronjob interval.
These values determine how many times the RRD file will miss data before inserting a NaN. The cronjob calls the cacti poller to start performing it's polling cycle. The poller interval is the actual time that the poller will wait between two polling cycles if it was indeed invoked in time by the cronjob.
So for 1 minute polling (on the poller and the cronjob) you will have to use a step of 60 (seconds) and a heartbeat of 120. For 5 minutes polling, the step will be 300 and the heartbeat will be 600.
This is mainly caused by someone changing the poller interval on the settings page.
Gandalf from the Cacti forums wrote a nice Guide that you can use and further help can be found on Cacti forums.
Good luck! :)