Polymix-4 to test Squid

Alex Rousskov rousskov at measurement-factory.com
Fri Feb 16 17:49:32 UTC 2018

On 02/15/2018 10:44 AM, Srivattsan s wrote:

> The web-polygraph setup for polymix-4 runs
> perfectly without the proxy (squid). I ran Simple.pg with proxy to see
> if my proxy setup is reachable and I was able to see responses for the
> simple.pg. 

Does your simple.pg use a subset of Polygraph agent IP addresses that
your PolyMix-4 is using? If not, it does not validate IP-level
connectivity of the PolyMix-4 setup.

> I am not sure where I am going wrong with polymix-4.

I trust you have checked system logs for relevant errors.

> The client starts well and goes into the i-framp phase while the server
> is waiting for the client to reach in the i-wait phase.

Your client is trying to send requests but is not getting any responses
-- the number of successful transactions and the number of errors is
always zero while the number of open sockets is growing. Furthermore,
the client has not printed the HTTP request headers of first
transaction. That probably means that the client cannot connect to
Squid; its TCP connection attempt is stuck.

Your server is not getting any requests -- the number of open sockets is
always equal to the number of server agents.

Thus, the problem is between Polygraph client (C) and Squid (P) and/or
between Squid and Polygraph server (S). Given your client behavior, I
would suspect the C-P connectivity first. Does the following produce
expected results during a running test?

1. C> ping -I # ping Squid

2. P> ping -I # ping a robot

3. C> telnet -b 3128
   and paste any garbage followed by two newlines.

... where "X>" means the command is to be executed on the X box
(assuming there are different boxes involved in the test).

* If #1 or #2 fail, then your IP routing is probably misconfigured.
* Otherwise, if #3 fails, there could be some weird firewall issue.
* Otherwise, you may want to collect packet dumps to triage further.

You can run similar tests to validate P-S connectivity as well, but my
bet is on the C-P segment.

> When I observe the Squid logs, I see no activity

Squid does not log a transaction until it is over. To see if Squid is
getting requests, use its cache manager interface (e.g., "squidclient
mgr:info"). You can also use tcpdump and such to see what packets Squid
is getting from Polygraph and what packets Squid is responding with.
Again, I suspect your Squid is not getting HTTP requests, but I do not
know whether it gets TCP handshake packets. Squid cannot know about the


P.S. Please post text logs, not images.

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