When using Realtime, if no graph contents are present an error is generated

[simonpunk]

Cacti version:
Version 1.2.12 (download from https://www.cacti.net/downloads/cacti-latest.tar.gz)

Bug:
After a fresh installation of cacti, it creates a device of my local machine automatically with some graph templates, all the graph templates can be displayed, and rrdtool debug says 'OK', but it still shows no data after half an hour, and I notice it keeps logging the same error message to cacti.log in every 11 seconds.

05/04/2020 10:11:14 - ERROR PHP NOTICE: Undefined variable: graph_contents in file: /opt/cacti/graph_realtime.php on line: 218
05/04/2020 10:11:14 - CMDPHP PHP ERROR NOTICE Backtrace: (/graph_realtime.php[218]:CactiErrorHandler())

I took a look at the latest commit of graph_realtime.php, seems it still didn't handle the $graph_contents properly as it can be null if it doesn't match one of the if cause.
I don't know what $graph_contents should be first defined.

[netniV]

You likely have a permissions problem creating the RRA oe RRA subfolders (if you are using the organised option).

The realtime graph is actually a separate issue that should be investigated in its own right. And is what I'm going to investigate here. Should you need further assistance on the "My graphs show no data" issue, I would refer to previous issues or the forums for more information as normally this is a configuration issue not a code issue.

[bmfmancini]

I have had no issues on Realtime I just put 1.2.12 in my lab and man I am not sure what was done but I see a noticble performance boost in how long it takes for the graph to populate

[netniV]

I'd be thanking @TheWitness for that one. This may be a specific issue with this setup if yours appears to be OK

[TheWitness]

Re-labeled this one as a Realtime Issue. There are actually two realtime issues with the 1.2.12 release. Going to fix both under this ticket. The issue with data sources not showing up is likely either permissions or poller related.

[TheWitness]

All fixed up now.

[simonpunk]

@TheWitness
Thanks, issue is fixed for me now!