A couple of questions about report

[Chengyu Fan]

Thanks a lot!

On Fri, Dec 9, 2011 at 2:06 PM, Dmitry Kurochkin <
dmitry.kurochkin at measurement-factory.com> wrote:

> On Fri, 9 Dec 2011 13:37:40 -0700, Chengyu Fan <chengy.fan at gmail.com>
> wrote:
> > Thanks for reply so soon.
> >
> > On Fri, Dec 9, 2011 at 7:11 AM, Dmitry Kurochkin <
> > dmitry.kurochkin at measurement-factory.com> wrote:
> >
> > > Hi Chengyu.
> > >
> > > On Thu, 8 Dec 2011 15:17:10 -0700, Chengyu Fan <chengy.fan at gmail.com>
> > > wrote:
> > > > Hi~ all,
> > > > Sorry I have some naive questions again.
> > > > I modify the simple download test in my experiment. And I generate
> the
> > > > report using polygraph-reporter.
> > > > I am a little confused about some parts in the report. At the end of
> this
> > > > test, the polygraph client cannot connect to the server side, and
> exits.
> > > > The generated report is attached. The questions are as follows:
> > > >
> > > > 1. The load trace graph shows the offered rate and measured rate,
> but it
> > > > only based on the client-side.
> > >
> > > If you mean the load trace figure on the "traffic rates, counts, and
> > > volumes" page, then yes.
> > >
> > > > So the client cannot distinguish the
> > > > measured rate comes from the proxy or the polygraph server, right?
> > >
> > > It can.  Otherwise Polygraph would not be able to calculate Hit ratio.
> > >
> > > > Is there
> > > > a graph we can directly check how many rate comes from proxy and how
> many
> > > > comes from the server?
> > > >
> > >
> > > If proxy is used, all replies the client receives come from the proxy,
> > > clients do not talk directly to the origin servers in this case.  Also
> I
> > > am not sure I understand what "how many rate" means.
> > >
> >
> > For "how many rates", I mean right now we know the measured rate from the
> > client side. But I don't know among all these measured rate, how many
> > measured rate comes from  server, and how many comes from proxy.
> > Is there a way to do that?
> >
>
> To collect detailed hits and misses stats, Polygraph needs the proxy to
> forward custom headers (X-Xact at least) in requests and replies.
>
> > Also, I noticed that in the load trace, the measured rate is not always
> > there. Sometimes I can only see the offered information. Why is this?
> >
>
> Apparently, in your test the proxy removes extension headers from
> forwarded messages.  That is why Polygraph can not collect detailed hits
> and misses stats.
>
> >
> > >
> > > There are "traffic rates, counts, and volumes" page has client-side
> > > reply traffic stream table at the end.  It contains contribution and
> > > rates stats for various reply types, including "misses" and "hits and
> > > misses".  That may be what you are looking for.  You can click on
> > > individual reply type to see detailed stats for it.
> > >
> > > Also the Details link on the index page goes to the index of all
> > > collected stats for all phases, both client and server sides.
> > >
> >
> > Yeah, I checked that. But in the traffic stream table, I found that the
> > misses is always 100%. But I do use a proxy, does this mean that the
> proxy
> > does not cache anything? And I checked log file, the server side rate is
> > much small than client sends. I think it is the proxy replies requests
> > instead of server. So why the misses is 100%?
> >
>
> I tried to explain why this happens above.  In your test the proxy does
> caching, you can see the aggregated hit ratio in the first table on the
> "hit ratios" page.  But detailed hits and misses stats can not be
> collected.
>
> >
> > >
> > > > 2. In hit ratios part, I find the measured number in the first table
> is
> > > > more than 79% (I set the recurrence is 80%). But in the client side
> hit
> > > > ratios, the measured number is 0. Why is that?
> > > >
> > >
> > > Polygraph relies on custom HTTP headers to calculate detailed hit
> > > stats.  If for some reason Polygraph can not get these headers
> > > (e.g. proxy does not forward it), detailed hit ratio stats can not be
> > > calculated.
> > >
> > > Polygraph still can measure the average hit ratio based on client and
> > > server stats (the first table on the "hit ratios" page).
> > >
> > > > 3. Also, I find the server side has lots of errors like "foreign host
> > > name"
> > > > and "missing target info in the request", does that mean the proxy
> does
> > > not
> > > > work well? Or this is the polygraph deliberately to do so?
> > > >
> > >
> > > "Missing target info in the request" means that proxy did not forward
> > > X-Target request header.
> > >
> > > "Foreign host name" means that Polygraph server received request for an
> > > unknown host (either in the request URI or the Host header).  Since you
> > > are using a single server, that means that proxy changed the host in
> > > some way.
> > >
> > > These issues are likely related to the missing client side stats
> > > problem.
> > >
> >
> > Do you mean, "foreign host name" and "missing target info in the request"
> > may be the reasons that there are such a high misses and no enough
> measured
> > information in my report?
> >
>
> "Foreign host name" errors seem like a separate issue.  I do not know
> why the proxy changes host in forwarded requests but it is weird.
>
> As for the "missing target info in the request" errors, they are not the
> reason, they are the consequence.  The root cause is that the proxy
> strips extension headers from the forwarded messages.  If you fix that,
> the errors would be gone and you would get detailed hits and misses
> stats.
>
> Regards,
>  Dmitry
>
> >
> > >
> > > > 4. I am also do not know what's the meaning of fill. Could you please
> > > > explain it?
> > > >
> > >
> > > Fill is a cachable miss, i.e. a reply that may increase (fill) the
> proxy
> > > cache.
> > >
> > > Regards,
> > >  Dmitry
> > >
> > > > Thanks.
> > > >
> > > > --
> > > > Regards,
> > > > Chengyu Fan
> > > > _______________________________________________
> > > > Users mailing list
> > > > Users at web-polygraph.org
> > > > http://www.web-polygraph.org/mailman/listinfo/users
> > >
> >
> >
> >
> > --
> > Regards,
> > Chengyu Fan
>



-- 
Regards,
Chengyu Fan
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