[Xymon] [PATCH] - DS override - http

[John Horne]

On Fri, 2019-05-17 at 12:34 +0000, John Horne wrote:
> Hello,
>
> Using the Terabithia RPMs, I've been looking at adding a 'DS' override entry
> to our analysis.cfg file.
>
> I have an entry for a web server as:
>
>   DS  http  tcp.http.https:,,weed.plymouth.ac.uk,.rrd:sec  >0.0007
> COLOR=yellow
>
> The comparison value (0.0007) was set low just to see that this was working.
> However, I can't get it to work. The 'http' column remains green, and the
> text shown of the http response (on the web page) indicates that the time is
> above the threshold value (e.g. 'Seconds: 0.088597000').
>
Hello,

Okay, the problem seems to be with the commas in the filename. Within the file
'xymond/client_config.c' exists the function 'check_rrdds_thresholds'. This is
used to check the DS rules, and checks the RRD filename against the one in the
rule. It does this by calling the function 'namematch' (found in
'lib/matching.c').

However, 'namematch' splits up the filename into tokens based on the comma
character. (Not sure why it does this, but I assume the function is used
elsewhere and makes sense in those cases.) As such, the filename never matches
if it contains a comma character (and mine has several of them).

A short context diff patch is attached, but I'm not sure it's the best.
Basically for the 'http' test don't call 'namematch' but call 'patternmatch'
instead. This is a similar function (also in matching.c), but doesn't split the
filename into tokens. It is usually used for matching substrings, but will work
when comparing two full filenames. It also takes care of regex rules. Using it
locally the patch seems to work fine.

The patch restricts calling 'patternmatch' only if the DS column name is
'http'. As far as I can tell this is the only time it is required. So it should
have no effect if DS is used elsewhere. However, others may be using DS with
other column names (I'm thinking 'apache' here), but which also use a filename
with commas. It may be that in those cases the bug will reappear unless the
column name is also tested for 'apache'.

As always, feel free to modify, or even reject, the patch.


As an addition, I did get the reported limits (&L and &U) reported with the
precision (significant digits) as used by the user in the analysis.cfg file.
So, in my case, '0.0007' has a precision of 4 set. The default text output when
using DS then uses this precision for all values. (It also took care of when
exponentiation was used, no leading zeros etc.) This all worked well. However,
the value reported for the RRD value (&V) seemed likewise restricted to 2
significant digits. I was loath to change this as it may well break things, and
seemed to be similarly restricted (to 2 digits) in more than one place. This
then meant that the output would generally look okay except for the reported
RRD value. As such I aborted that patch.



John.

--
John Horne | Senior Operations Analyst | Technology and Information Services
University of Plymouth | Drake Circus | Plymouth | Devon | PL4 8AA | UK
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