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Subject: RE: Buggy mod_jk2 AJP 13  communications?
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Date: Thu, 10 Jul 2003 17:19:12 -0700
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 <9537E22704C8274AAD53C5193A501F00015920@camail01.ipcfcdom.inphonic.com>
Thread-Topic: Buggy mod_jk2 AJP 13  communications?
Thread-Index: AcNF9Cunmk41ILYPS5mw0nM/kOf4NABTH2Rg
From: "James Courtney" <Jcourtney@inphonic.com>
To: "Tomcat Developers List" <tomcat-dev@jakarta.apache.org>

Henri,
	thanks a million for your help.  I think I'll try out jk2 2.0.2 and =
while that's being tested work out jk 1.2.4 as a fall back.  Do you have =
any thoughts on the use of the channel socket options nodelay, timeout, =
and keepalive.  I'm also thinking that having the connectionTimeout set =
to 0 or -1 (infinite) for my JK2 CoyoteConnector is not good either =
because if something get's wedged the server never drops the socket.  It =
would be great to see some additional documentation on these use of =
these options.

Interestingly Nagle is defaulted to off  (nodelay on) in the Java side =
of the connectors in Tomcat 4.1.24 (see ChannelSocket.java) and turned =
on (nodelay off) by default in the Apache (see jk_channel_socket.c).  =
According to Stevens UNIX Network Programming Volume 1, Second Edition, =
Nagle is on by default in Unix systems.

Anyones input on the use of these options would be great.

Thanks!

Jamey

James Courtney
InPhonic, Inc.

-----Original Message-----
From: Henri Gomez [mailto:hgomez@apache.org]
Sent: Wednesday, July 09, 2003 1:30 AM
To: Tomcat Developers List
Subject: Re: Buggy mod_jk2 AJP 13 communications?


James Courtney a =E9crit :

> Developers,
> 	Forgive the post to the developer list but I honestly feel that my =
question(s) are detailed enought to be of interest to the development =
community for Tomcat and have thus far remained largely unaddressed by =
the tomcat-user community.  Please also forgive the length of the email =
but as a developer I try to provide any and all information that I've =
gathered to give anyone willing to help me as much relevant information =
as possible.  Please keep in mind while reading and formulating your =
answer(s) that I really don't have the luxury of taking wild stabs in =
the dark with this as it's a current production problem for us.  I need =
to know the best course of action to take to correct our systems to =
provide reliable service to our users.
>=20
> We recently launched our application running on 2 Tomcat =
4.1.24/JDK1.4.1/Sun 2.8/Sparc machines load balanced by an Apache =
2.0.45/Sun2.8/Sparc machine using mod_jk2.  Throughout testing =
(including some basic load testing) we experienced very good behavior =
from our cluster and are in general very pleased with the performance =
over our previous system of Apache 1.3.19/Tomcat 3.2.2/mod_jk.  We built =
our mod_jk2 Apache module using the 4.1.24 Tomcat-Connectors source =
release provided with the Tomcat 4.1.24 release.  This seems to be =
slightly more recent than the last public release of mod_jk2 which I =
think was 2.0.2 according to CVS and what I've read.
>=20
> Our problem is that we notice intermittent and not infrequent lapses =
in our application.  These appear as very slow performance or complete =
lack of connectivity to the Apache server but each of the Tomcat servers =
is functioning normally when we connect directly to those.
>=20
> Apache serves no contect, static or dynamic, and everything is pushed =
to the Tomcat servers as the bulk of our page content is dynamic and we =
decided to keep the config simple at the expense of a little network =
performance on what static content we have.
>=20
> It's about the peak time of day for us and we have 50-60 active TCP =
connections from our Apache server to EACH Tomcat server, all in the =
ESTABLISHED state according to netstat.  We have an additional 220 or so =
TCP connections from the internet to our Apache server of which about 30 =
are ESTABLISHED, about 20 are FIN_WAIT (and FIN_WAIT_2), and about 170 =
are TIME_WAIT.
>=20
> Assuming ajp13 works like HTTP1.1 this all makes sense as the Apache =
would keep sockets open to the Tomcats and internet users opening and =
closing connections and browsers to the Apache would probably create a =
pattern like that above.
>=20
> I've attached several of our config files for your reference:
> 1) httpd.conf (for Apache or course)    =20
> 2) workers2.properties (for mod_jk2 of course)
> 3) server.xml (from one Tomcat, both are indentical with exception of =
jvmRoute)
> 4) jk2.properties (Still don't know the point of this but here it is)
> 3) apache.info (a dump using httpd -V)
>=20
>=20
> I have several general questions which I feel can only be answered by =
those fairly familiar with the mod_jk/jk2 code.
>=20
> 1) Which is the preferred connector at this time in terms of =
reliability and scalability.

mod_jk is the preferred in term of reliability since it's older and more =

tested, but jk2 is the future.

> 2) What is the preferred version/release of that connector.

mod_jk 1.2.5 should be release soon.

> 3) Should both the java and c/apache side of the connector be built =
and installed together onto Tomcat 4.1.24 for compatibility or is the =
c/apache side alone sufficient to work reliably with the =
CoyoteConnector/JkCoyoteHandler packaged with the 4.1.24 build?

mod_jk should be built from jakarta-tomcat-connectors release.

> 4) Does Apache mod_jk(2) pool a set of connections to Tomcat not to =
exceed the maxProcessors parameter of the Tomcat CoyoteConnector?  Could =
my connections be timing out?  Should I set connectionTimeout to -1 =
(it's currently 0)?

The rule is that the MAX NUMBERS of HTTPD connexions should be less than =

the maxProcessors in ajp13. For instance if you have 2 tomcat with each=20
150 maxProcessors, you should restrict Apache HTTPD to have not more=20
than 250 connexions

> 5) What parameters affect mod_jk(2) performance.  I see from the code =
that the Channel.Socket (as of the TOMCAT_4_1_24 CVS tag) will accept =
settings for timeout, keepalive,=20
and nodelay but that these are not documented.  Could these help?

See the nodelay (NAAGLE related)

> 6) Could my Apache 2.0.45 just be foobar?  This seems unlikely, the =
config is pretty straight forward.

I'm using Apache 2.0.46 with Tomcats (3.3.1a) and mod_jk 1.2.4 and have=20
no problems with it. In my situation Apache server static contents like=20
images and css.

Regards


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