[xymon] hobbitgraph.cgi: Attempting to reuse 'mysqlht'

Mon Nov 29 22:54:47 CET 2010

On Sun, 28 Nov 2010 16:30:39 +0200, Arie Skliarouk wrote:

> On Thu, Nov 25, 2010 at 17:59, Henrik Størner <henrik at hswn.dk> wrote:
> 
>> On Wed, 24 Nov 2010 16:12:07 +0200, Arie Skliarouk wrote:
>>
>> > I created a custom mysql parameters check that shows graphs on one
>> > server, but not on the other. hobbitgraph.sh (hobbitgraph.cgi?) kept
>> > sending following error instead of the actual image:
>> > <html><head><title>Invalid request</title></head> <body>Attempting to
>> > reuse 'mysqlht'</body></html>
>>
>> This is an error from the rrdtool library. So I would suspect something
>> dodgy with the graph-definition in hobbit-graphs.cfg, or the RRD file
>> data is not as you would expect.
>>
>> Could you show us the graph definition you use ?
> 
> 
> See attached.

OK, the interesting part of your graph definition looks like this:

[mysql]
    FNPATTERN mysql.rrd
    TITLE MySQL
    YAXIS Number
    DEF:mysqlht=@RRDFN@:mysqlht:AVERAGE
    DEF:mysqlhs=@RRDFN@:mysqlhs:AVERAGE
    DEF:mysqlhq=@RRDFN@:mysqlhq:AVERAGE
    LINE2:mysqlht#00CCCC:MySQL threads
    LINE2:mysqlhs#ff0000:Slow queries
    LINE2:mysqlhq#ff00ff:Queries per sec

The problem occurs because you're using an FNPATTERN definition, but you
only expect one file to match. I'll bet that the problem host has another
RRD file present which matches "mysql.rrd" - there is no anchor in the
pattern, so a file "blablamysql.rrd" will also match this pattern. Or
even "mysql.rrd.old".

When you have multiple files that match FNPATTERN, the rest of the 
definition is repeated for each file when Xymon tells RRDtool how to 
generate the graph. So you'll end up with two DEF lines that define a 
"mysqlht" variable - one for each file that matches FNPATTERN. That
is not allowed, and causes RRDtool to complain with the error you see.

If you only want to use one specific RRD file, don't use FNPATTERN.
Instead, put the filename where you have "@RRDFN@" now:

[mysql]
    TITLE MySQL
    YAXIS Number
    DEF:mysqlht=mysql.rrd:mysqlht:AVERAGE
    DEF:mysqlhs=mysql.rrd:mysqlhs:AVERAGE
    DEF:mysqlhq=mysql.rrd:mysqlhq:AVERAGE
    LINE2:mysqlht#00CCCC:MySQL threads
    LINE2:mysqlhs#ff0000:Slow queries
    LINE2:mysqlhq#ff00ff:Queries per sec

Just for the record, if you DO want to match multiple files, then you 
must include the index-number in the DEF and GPRINT definition. E.g.

[mysql]
    FNPATTERN mysql.rrd
    TITLE MySQL
    YAXIS Number
    DEF:mysqlht at RRDIDX@=@RRDFN@:mysqlht:AVERAGE
    DEF:mysqlhs at RRDIDX@=@RRDFN@:mysqlhs:AVERAGE
    DEF:mysqlhq at RRDIDX@=@RRDFN@:mysqlhq:AVERAGE
    LINE2:mysqlht at RRDIDX@#@COLOR@:@RRDPARAM@ MySQL threads

See e.g. the [la] and [disk] definitions in the standard graphs.cfg / 
hobbitgraph.cfg file.

Regards,
Henrik