Re: Persistent Connection Issue

On Fri, 2006-04-07 at 12:02 -0700, Isaac Cheung wrote:
> I have previously executed workload with polygraph 2.8.1 on Linux
> 2.4.21-40 having pconn_use_lmt set to zipf(16). But, I found out from
> the SQUID persistent conn utilitization histrograms that there were
> only 1req connections accepted meaning there were no persistent conn
> established.
>
> To validate the proxy setup, I further tested it with a connected
> browser and persistent connections were indeed established.
>
> With pconn_use_lmt set to zipf(16) and http_versions set to the
> default are there other parameters that I need to set in order to
> enable pconn?

I do not think so. There is also a related persistent connection timeout
parameter (idle_pconn_tout), but it is optional. I would do the
following:

1. Check that you are setting pconn_use_lmt on the right side(s). The
option is valid for Polygraph robots and servers.

2. Grab a few HTTP requests and responses (e.g., via tcpdump/show or
ethereal). Check whether Polygraph is _not_ sending "Connection: close"
HTTP header in the HTTP/1.1 request. Check that Squid is sending
"Connection: keep-alive" in the HTTP/1.0 response. If the HTTP versions
or message headers differ from the expected ones, we may be able to find
the culprit.

> Or are there other conditions that will cause persistent connections
> not to be used?

On Polygraph side, errors and similar abnormal conditions close a
persistent connection. The server (including Squid) can signal
connection close by sending "Connection: close" in an HTTP/1.1 response
or sending nothing in an HTTP/1.0 response. On Squid side, there may be
many other factors (e.g., load).

Sorry for the delayed response. Please keep me posted on your progress.

Thank you,

Alex.
Received on Wed Apr 12 17:28:43 2006