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From "Chirouze Olivier" <olivier.chiro...@volvo.com>
Subject RE: [users@httpd] Apache 2.0.58 + Solaris 5.9: status "...reading..." & TCP state "FIN_WAIT_2"
Date Fri, 26 Jan 2007 16:41:57 GMT
Hi,

Thanks for your prompt reply. We will definitively upgrade soon, just
"to be up to date"... But because nothing is said about that point in
docs I'm wondering if that will make any difference...

Anyway, we're providing both HTTP and HTTPS. Might be interesting to try
recognize if this happens on both? I will have a look at it.

Do you think you might give me the values of the following Unix params
on your Solaris 9 installs?

tcp_fin_wait_2_flush_interval
tcp_keepalive_interval
tcp_ip_abort_interval

Thanks in advance,

Olivier

Olivier CHIROUZE
I&0 Infrastructure
Volvo Information Technology

-----Original Message-----
From: Richard de Vries [mailto:richard_devries@yahoo.com] 
Sent: 26 January 2007 17:35
To: users@httpd.apache.org
Subject: Re: [users@httpd] Apache 2.0.58 + Solaris 5.9: status
"...reading..." & TCP state "FIN_WAIT_2"

Interesting problem.

I am running Apache 2.0.59 as a reverse proxy on multiple Solaris 9 and
AIX servers and have never encountered these types of issues. Perhaps
you should try upgrading to 2.0.59 on one of your development machines
and see if that makes a difference. If not, it is most likely an OS
and/or configuration issue.

What other plugins are you running? Also, is this HTTP proxying, or
HTTPS?

----- Original Message ----
From: Chirouze Olivier <olivier.chirouze@volvo.com>
To: users@httpd.apache.org
Sent: Friday, January 26, 2007 9:56:46 AM
Subject: [users@httpd] Apache 2.0.58 + Solaris 5.9: status
"...reading..." & TCP state "FIN_WAIT_2"


Hi all,

I'm facing a quite tricky situation with Apache 2.0.58 running on
Solaris 5.9.

Apache is running as a reverse proxy (mod_proxy + mod_rewrite).
The maximum concurrent connections is set to 150.

Because we reached the maximum a few times and got the reverse proxy
saturated, we started monitoring the Apache status page (/status).
We noticed that many requests were in the "..reading.." state (up to
40!), and they block a lot of slots.

At first, we upgraded from 2.0.47 to 2.0.58 because it seemed there was
a security hole in the earlier, fixed in 2.0.48.
I found some explanation here:
http://www.monkeybrains.net/~rudy/example/server_busy_state.html.

The thing is, the situation is starting to appear again with 2.0.58.

We've gone down to Unix and found that most of these requests were in
"FIN_WAIT_2" TCP state, and for a while (approx. 8min!!).

We found this: http://httpd.apache.org/docs/2.0/misc/fin_wait_2.html.
What it says, in a word, is that these things can happen and are
"normal": the connection stays in "FIN_WAIT_2" state until the timeout,
if clients do not close it properly. They just say it can be a problem
on the Unix point of view because.
I don't know if this is still true for 2.0 because the article was just
copied from 1.3. The thing is, it says that "The connections in
FIN_WAIT_2 do not tie up an httpd process". For us, IT DOES! Every
"..reading.." request happend to be in the "FIN_WAIT_2" state.

We have contacted Sun to get their opinion. The short answer is "you can
change the FIN_WAIT_2 timeout but be careful because wrong tuning will
have negative impact. Maybe you should wonder why these connections stay
alive". As far as I understood, the connection is not closed by the
client. The server (Apache) does nothing wrong. But maybe it does, as it
doesn't leave the process free?

My questions are:
Does anyone have heard about similar problems?
Why do these connections hold a process of Apache while the
documentation says it doesn't?
Do you recon tuning the Unix timeout would help? (current value of
tcp_fin_wait_2_flush_interval: 675000 ms - 11min!! This looks just
huge!)

Thanks in advance,

Olivier

Olivier CHIROUZE
I&0 Infrastructure

Volvo Information Technology




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