A couple of questions about report

Chengyu Fan chengy.fan at gmail.com
Fri Dec 9 20:37:40 UTC 2011

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?

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?

> 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%?

> > 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?

> > 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

Chengyu Fan
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