[QA 1.3] graph error image does not contain any information

[xmacan]

Display graph debug information if rrd file is missing says a lot of information:

• image with "Failed to open data file ..."
• correct rrdtool command
• RRDtool Says: ERROR: opening '/usr/local/share/cacti/rra/pokus_fg_snmp_oid_35399.rrd': No such file or directory

In 1.3 I get only:

• image unknown rrdtool error
• empty rrdtool command
• empty rrdtool Says:

[xmacan]

I had only few minutes for debug now. It seems that the code is very similar to 1.2.x. I don't know if it is any small bug or any bigger issue. I can look at it.
@TheWitness any advice?

[xmacan]

@TheWitness I found it. Please check lib/rrd.php line 1815.
Someone add these lines:
if (!rrdtool_file_exists($data_source_path, $rrdtool_pipe)) {
return false;
}

It causes my issue. Without lines it works well. But I do not know the consequences of my modification or the reason for this condition. Please have a look at it

[TheWitness]

Yea, we need to improve that. The file missing was causing other issues with export and ptile data. So, I think we can simply change the check to not fail if it's not export for example.