Re: Issues with Cacti running very long rrdtool commands

To follow up on this, I did some tests with the graph that is failing vs
the graph that is working by adding:

print strlen($command_line);

inside the following function in rrd.php:

function rrdtool_execute

The graph that fails has a string length of 131104, the graph that succeeds
has a string length of 130864.  So, it would seem as though we are running
into a 131072 limitation.

Any ideas how we can get around this, or get Cacti to run the command as if
it were at the command prompt which does not seem to have such a limitation?

Cheers,

Ryan

On Wed, Oct 22, 2014 at 9:47 PM, Ryan Garland <[email protected]> wrote:

> I believe I am running into a character limit for the commands that
> rrdtool can successfully run.
>
> I currently have a stacked aggregate graph with 1376 line items (3/4 of
> which are the Legend lines).  This graph renders just fine, and with Debug
> mode turned on, after the long rrdtool command, rrdtool returns "OK".  The
> character count of the command (including any white space) of this command
> is 132961.  (Yes, I know that's a lot - I have my reasons :))
>
> However, as soon as I add a new line item to the graph, the graph no
> longer renders, and with Debug mode turned on, rrdtool does not return OK
> -- it merely shows nothing.  The character count of this command is 133204.
>
> Here's the kicker:  When the failing rrdtool command is manually ran at
> the system's command prompt, the command succeeds.  It seems that only
> within Cacti does the rrdtool command not work.
>
> I have done a lot of research and found some seemingly related information
> ( such as http://www.mail-archive.com/[email protected]/msg05522.html )
> which discusses command length limitations by the OS / kernel, limiting to
> 131072 MAX_ARG_STRLEN, but:
>
> 1) this number is slightly lower than the length of the full rrdtool
> command that is succeed, and
> 2) if that was the problem, the command should not succeed when manually
> run at the command prompt
>
> So what is Cacti doing when it runs rrdtool that could be limiting the
> command length?  Does anyone have any suggestions as to how to resolve this
> apparent limitation?
>
> Any help is appreciated.  Software versions listed below.
>
> Cacti Version 0.8.8a
> PHP Version 5.3.10-1ubuntu3.14
> Ubuntu Version 12.04
> RRDTool Version 1.4.x
>
> Ryan
>
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