A couple of questions about report

Dmitry Kurochkin dmitry.kurochkin at measurement-factory.com
Fri Dec 9 14:11:56 UTC 2011

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.

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.

> 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

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

> 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


> Thanks.
> -- 
> Regards,
> Chengyu Fan
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