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<p class=MsoNormal><span style='color:#1F497D'>So far, from my investigations,
it seems that you <i>can</i> make MRTG/rrdcached work, but there are a few
important points –<o:p></o:p></span></p>
<p class=MsoListParagraph style='text-indent:-18.0pt;mso-list:l0 level1 lfo1'><![if !supportLists]><span
style='color:#1F497D'><span style='mso-list:Ignore'>1.<span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]><span style='color:#1F497D'>It will not work at
all via TCP, only via unix sockets since create and info are not supported by
rrdcached, and MRTG tests for existence of the rrd file by looking for it in
the filesystem. <o:p></o:p></span></p>
<p class=MsoListParagraph style='text-indent:-18.0pt;mso-list:l0 level1 lfo1'><![if !supportLists]><span
style='color:#1F497D'><span style='mso-list:Ignore'>2.<span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]><span style='color:#1F497D'>You need to modify
the mrtg code about line 894 to so that updatev is not used (as rrdcached doesn’t
support updatev)<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:36.0pt'><span style='color:#1F497D'>
</span><span style='color:black'>if ( $RRDs::VERSION >= 1.2 and
($RRDs::VERSION <1.4 or !$ENV{RRDCACHED_ADDRESS})){<o:p></o:p></span></p>
<p class=MsoListParagraph style='text-indent:-18.0pt;mso-list:l0 level1 lfo1'><![if !supportLists]><span
style='color:#1F497D'><span style='mso-list:Ignore'>3.<span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]><span style='color:#1F497D'>If you make the
updatev check above, then you also kill off any thereshold checking unless you
make a similar change lower down, which would force cache flushing and remove
much of the cache benefit. Fortunately, we don’t use thresholding.<o:p></o:p></span></p>
<p class=MsoListParagraph style='text-indent:-18.0pt;mso-list:l0 level1 lfo1'><![if !supportLists]><span
style='color:#1F497D'><span style='mso-list:Ignore'>4.<span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]><span style='color:#1F497D'>Since the web
frontend doesn’t query via the cache (since rrdcached doesn’t support
graph, fetch or info) you can end up with displayed data lagging behind
slightly.<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>Seems that in order for this to
work smoothly, we need the rrdcached code to be improved to support create,
info,fetch and preferably tune; and also the MRTG code to be enhanced to be
rrdcached-aware. Possibly rrdcached could be modified to fork off an
rrdtool process to handle the difficult things like ‘create’,
though ‘info’ and ’fetch’ would probably need to be
done internally.<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>I’ve noticed there was
some discussion on this in the rrdtool mailing lists back in Jan/Feb this year,
but nothing more since.<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>Steve<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<div>
<div class=MsoNormal align=center style='text-align:center'><span lang=EN-US
style='color:#1F497D'>
<hr size=2 width="100%" align=center>
</span></div>
<p class=MsoNormal><b><span style='color:#1F497D'>Steve Shipway<o:p></o:p></span></b></p>
<p class=MsoNormal><span style='font-size:10.0pt;color:#1F497D'>ITS Unix
Services Design Lead<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;color:#1F497D'>University of
Auckland, New Zealand<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;color:#1F497D'>Floor 1, 58
Symonds Street, Auckland<o:p></o:p></span></p>
<p class=MsoNormal><i><span style='font-size:10.0pt;color:#595959'>Phone: +64
(0)9 3737599 ext 86487<o:p></o:p></span></i></p>
<p class=MsoNormal><i><span style='font-size:10.0pt;color:#595959'>DDI: +64
(0)9 924 6487<o:p></o:p></span></i></p>
<p class=MsoNormal><i><span style='font-size:10.0pt;color:#595959'>Mobile: +64
(0)21 753 189<o:p></o:p></span></i></p>
<p class=MsoNormal><i><span style='font-size:10.0pt;color:#595959'>Email: <a
href="mailto:s.shipway@auckland.ac.nz"><span style='color:#595959'>s.shipway@auckland.ac.nz</span></a><o:p></o:p></span></i></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:18.0pt;font-family:Webdings;
color:green'>P</span><span lang=EN-GB style='color:blue'> </span><span
lang=EN-GB style='font-size:10.0pt;font-family:"Arial Narrow","sans-serif";
color:green'>Please consider the environment before printing this e-mail</span><span
lang=EN-GB style='color:blue'> </span><span lang=EN-GB style='font-size:7.5pt;
font-family:"Verdana","sans-serif";color:navy'><o:p></o:p></span></p>
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<p class=MsoNormal><o:p> </o:p></p>
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