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Posted to users@tomcat.apache.org by John Oliver <jo...@john-oliver.net> on 2009/04/06 23:15:00 UTC

ajp_read_header: ajp_ilink_receive failed

[Sun Mar 29 04:05:33 2009] [error] ajp_read_header: ajp_ilink_receive
failed
[Sun Mar 29 04:05:33 2009] [error] (120006)APR does not understand this
error code: proxy: read response failed from (null) (localhost)

I get these messages a *lot* in my ssl_error_log  Google isn't helping,
and I've had no response on the httpd list, so i'm hoping someone here
can steer me in the right direction.

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* John Oliver                             http://www.john-oliver.net/ *
*                                                                     *
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Re: ajp_read_header: ajp_ilink_receive failed

Posted by Rainer Jung <ra...@kippdata.de>.
On 07.04.2009 01:01, John Oliver wrote:
> On Tue, Apr 07, 2009 at 12:40:42AM +0200, Rainer Jung wrote:
>>> [Sun Mar 29 04:05:33 2009] [error] ajp_read_header: ajp_ilink_receive
>>> failed
>>> [Sun Mar 29 04:05:33 2009] [error] (120006)APR does not understand this
>>> error code: proxy: read response failed from (null) (localhost)
>>
>> 120006 should be AJP_ENO_HEADER, which means after sending a request to
>> the backend, Apache was not able to receive the headers of the response.
>>
>> This could have multiple reasons, like a timeout while waiting for the
>> response, and maybe also a backend closing a connection due to an idle
>> timeout. You should configure Cping/Cpong on mod_proxy_ajp (with a
>> recent version) to allow for robust detection of a broken backend.
> 
> OK...
> 
> What is the "CPING / CPONG For Dummies" version? :-)
> 
> I found
> http://tomcat.apache.org/connectors-doc/generic_howto/timeouts.html
> which doesn't really help me... it presupposes that I know an awful lot
> more than I do.
> 
> Is there a walkthrough somewhere that tells me how I'd go about CPINGing
> and CPONGing that starts with the assumption that I have no idea what
> they are? :-)

The docs for the configuration of all mod_proxy sub modules (like
mod_proxy_ajp) are combined in

http://httpd.apache.org/docs/2.2/mod/mod_proxy.html

Look for "CPING" in the page and then have a look at all those
configuration attributes contained in the surrounding table. Many of
those are well explained. If not, aks here again or on the httpd list.
The CPING for mod_proxy_ajp and for mod_jk (that's the docs page you
found) work the same way. CPING sends an AJP packet to the backend, that
has an empty body (contains no http request). Such a packet is
immediately answered by the connector of the backend with minimal
processing and ensures, that the connection is still working and there
is something speaking AJP13 on the other side. Overhead is very small,
so it's fine to use it before every request.

Regards,

Rainer

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Re: ajp_read_header: ajp_ilink_receive failed

Posted by John Oliver <jo...@john-oliver.net>.
On Tue, Apr 07, 2009 at 12:40:42AM +0200, Rainer Jung wrote:
> > [Sun Mar 29 04:05:33 2009] [error] ajp_read_header: ajp_ilink_receive
> > failed
> > [Sun Mar 29 04:05:33 2009] [error] (120006)APR does not understand this
> > error code: proxy: read response failed from (null) (localhost)
> 
> 
> 120006 should be AJP_ENO_HEADER, which means after sending a request to
> the backend, Apache was not able to receive the headers of the response.
> 
> This could have multiple reasons, like a timeout while waiting for the
> response, and maybe also a backend closing a connection due to an idle
> timeout. You should configure Cping/Cpong on mod_proxy_ajp (with a
> recent version) to allow for robust detection of a broken backend.

OK...

What is the "CPING / CPONG For Dummies" version? :-)

I found
http://tomcat.apache.org/connectors-doc/generic_howto/timeouts.html
which doesn't really help me... it presupposes that I know an awful lot
more than I do.

Is there a walkthrough somewhere that tells me how I'd go about CPINGing
and CPONGing that starts with the assumption that I have no idea what
they are? :-)

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* John Oliver                             http://www.john-oliver.net/ *
*                                                                     *
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Re: ajp_read_header: ajp_ilink_receive failed

Posted by Rainer Jung <ra...@kippdata.de>.
On 07.04.2009 00:08, Christopher Schultz wrote:
> On 4/6/2009 5:51 PM, John Oliver wrote:
>> RHEL 5.2, httpd-2.2.3-11.el5_1.3, tomcat5-5.5.23-0jpp.7.el5_2.1
> 
> 2.2.3 is pretty old... any chance of upgrading to 2.2.11? You're nearly
> 3 years out of sync with the state-of-the-art.

++1

mod_proxy_ajp was new in 2.2.x and did mature. If you want to use it,
update and have a look at pool sizing an timeout configuration.

> Well, let's get the ajp thing fixed first, then move on to the other
> problems. It's midnight in Germany and Croatia. Give Rainer and Mladen a
> chance to read this thread and give you some thoughts on the ajp stuff.

Hmm, still around midnight. Nevertheless:

> [Sun Mar 29 04:05:33 2009] [error] ajp_read_header: ajp_ilink_receive
> failed
> [Sun Mar 29 04:05:33 2009] [error] (120006)APR does not understand this
> error code: proxy: read response failed from (null) (localhost)


120006 should be AJP_ENO_HEADER, which means after sending a request to
the backend, Apache was not able to receive the headers of the response.

This could have multiple reasons, like a timeout while waiting for the
response, and maybe also a backend closing a connection due to an idle
timeout. You should configure Cping/Cpong on mod_proxy_ajp (with a
recent version) to allow for robust detection of a broken backend.

Regards,

Rainer

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Re: ajp_read_header: ajp_ilink_receive failed

Posted by Christopher Schultz <ch...@christopherschultz.net>.
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

John,

On 4/6/2009 6:50 PM, John Oliver wrote:
> On Mon, Apr 06, 2009 at 06:08:54PM -0400, Christopher Schultz wrote:
>> -----BEGIN PGP SIGNED MESSAGE-----
>> Hash: SHA1
>>
>> John,
>>
>> On 4/6/2009 5:51 PM, John Oliver wrote:
>>> RHEL 5.2, httpd-2.2.3-11.el5_1.3, tomcat5-5.5.23-0jpp.7.el5_2.1
>> 2.2.3 is pretty old... any chance of upgrading to 2.2.11? You're nearly
>> 3 years out of sync with the state-of-the-art.
> 
> Tell it to Red Hat...

It's interesting how these distro maintainers act with regard to
packages. IFAICT, their stance is that they spend a /long/ time vetting
a particular package (let's say httpd 2.2.3) and then they go ahead and
allow their customers to use it. Any security patches that come out for
it will be applied, re-tested, and then released (that's why you see the
"-11.el5_1.3" on the end of the official release number), but all other
patches are ignored.

Since it apparently takes so long to vet a new release, they don't
bother to do it for every release... they just apply the security
patches and consider it "stable". Unfortunately, big bug fixes that
don't have anything to do with security (hey, mod_proxy_ajp is plenty
secure because it doesn't allow communication!) don't make it into the
distro.

I know that Debian has different "branches" that you can follow
depending on your level of paranoia about breaking things: security,
stable, unstable, etc. Does Red Hat have anything like that? It's
possible that you have (possibly unintentionally) stuck your Apache
httpd version at a particular release level for fear of breaking
something that is working. My sense is that a minor-version upgrade
shouldn't break anything at all (unless there is some kind of
regression)... just make sure you test everything before you put it into
production.

>> $ java -version
> 
> [root@mda-services ~]# java -version
> java version "1.6.0_05"
> Java(TM) SE Runtime Environment (build 1.6.0_05-b13)
> Java HotSpot(TM) Server VM (build 10.0-b19, mixed mode)

Good. The presence of the gcj should not interfere as long as the /real/
Java is the one being used by Tomcat. I suspect it is, but you can
always check with a simple JSP or something that dumps out the system
properties (System.getProperties().list(System.out) ought to do the trick).

> The only config I'm aware of is /etc/httpd/conf.d/proxy_ajp.conf, which
> consists of lines like:
> 
> ProxyPass /GmmsL/ ajp://localhost:8009/GmmsL/
> 
> I just add another similar line for each app.

Okay, that's mod_proxy_ajp alright. As Rainer mentioned, there have been
a /lot/ of improvements to mod_proxy_ajp since your version was
released. I recommend working with Red Hat on a solution. Maybe they'll
do a custom build for you... you /are/ paying them for support, afterall :)

>> I've had the JVM crash crash (for different issues) and I've run out of
>> memory, but Tomcat has never failed me. The most likely reason for
>> "server instability" is, sadly, your own application. We might be able
>> to help with that, too.
> 
> That would rock :-)

Come on back when you've got this AJP thing worked out.

If Tomcat stops responding, take a few thread dumps (send a SIGQUIT to
the main Java process, or use 'jstack') a few seconds apart. One or two
over a 20-30 second time period should be enough. This will dump a stack
trace for all running threads to stdout (which can be redirected to a
file if using jstack, or collected from catalina.out if using SIGQUIT).
These will help a lot in determining what the problems might be.

Good luck,
- -chris
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Re: ajp_read_header: ajp_ilink_receive failed

Posted by John Oliver <jo...@john-oliver.net>.
On Mon, Apr 06, 2009 at 06:08:54PM -0400, Christopher Schultz wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> John,
> 
> On 4/6/2009 5:51 PM, John Oliver wrote:
> > RHEL 5.2, httpd-2.2.3-11.el5_1.3, tomcat5-5.5.23-0jpp.7.el5_2.1
> 
> 2.2.3 is pretty old... any chance of upgrading to 2.2.11? You're nearly
> 3 years out of sync with the state-of-the-art.

Tell it to Red Hat...

> > There is no firewall... Tomcat and httpd are on the same box.
> 
> iptables could be interfering, but not likely. Most people don't bother
> protecting localhost from itself :)

Even if the app works?  Some of these systems have some "default"
iptables.  Others have something else.  Until I understand why which is
what, I try to let things be.

> > I'm not sure how to check the JVM version... this is the first time I've
> > ever had to worry about Tomcat and Java stuff, so I'm doing a lot of
> > guessing.
> 
> $ java -version

[root@mda-services ~]# java -version
java version "1.6.0_05"
Java(TM) SE Runtime Environment (build 1.6.0_05-b13)
Java HotSpot(TM) Server VM (build 10.0-b19, mixed mode)

> > [root@mda-services ~]# rpm -qa | grep java
> > java-1.4.2-gcj-compat-devel-1.4.2.0-40jpp.115
> > gcc-java-4.1.2-42.el5
> > java-1.4.2-gcj-compat-1.4.2.0-40jpp.115
> 
> Hmm... it's probably /not/ your problem, here,  but a /lot/ of people
> have had problems with the gcj version of Java. Fortunately, you're
> taking care of SSL through Apache httpd: that's where I've heard of lots
> of incompatibilities and simply incorrect (or very surprising) operation
> and/or crashes.
> 
> I would recommend using Sun's Java. I'd also recommend a newer version
> (they're on 1.6 these days... 1.4 is a dinosaur).

I think I am... :-)  I'm guessing that version was installed some other
way, and the Red Hat packages aren't being used?

> > It seems to work, even with all of these error messages, but this
> > setup nwas cobbled together by developers.
> 
> So, are you using mod_proxy_ajp? Please post your configuration. I have
> had much better luck with mod_jk, but I think that's more due to my
> history with it than anything else: I simply have the experience with
> mod_jk and not with mod_proxy_ajp.

The only config I'm aware of is /etc/httpd/conf.d/proxy_ajp.conf, which
consists of lines like:

ProxyPass /GmmsL/ ajp://localhost:8009/GmmsL/

I just add another similar line for each app.

> 
> > Also, Tomcat seems to be pretty unstable and needs to be restarted
> > every week or so, and I wouldn't be surprised if these errors have
> > something to do with that.
> 
> Tomcat itself is super stable. I have never ever had it crash on me.

I didn't mean to blame Tomcat itself.  I'm sure that whatever problem is
because someone hacked at something until it was "good enough", and then
walked away and forgot all about it :-)

> I've had the JVM crash crash (for different issues) and I've run out of
> memory, but Tomcat has never failed me. The most likely reason for
> "server instability" is, sadly, your own application. We might be able
> to help with that, too.

That would rock :-)

Thanks, Chris.

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* John Oliver                             http://www.john-oliver.net/ *
*                                                                     *
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Re: ajp_read_header: ajp_ilink_receive failed

Posted by Christopher Schultz <ch...@christopherschultz.net>.
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Hash: SHA1

Chuck,

On 4/6/2009 6:30 PM, Caldarale, Charles R wrote:
>> From: Christopher Schultz [mailto:chris@christopherschultz.net]
>> Subject: Re: ajp_read_header: ajp_ilink_receive failed
>>
>>> [root@mda-services ~]# rpm -qa | grep java
>>> java-1.4.2-gcj-compat-devel-1.4.2.0-40jpp.115
>>> gcc-java-4.1.2-42.el5
>>> java-1.4.2-gcj-compat-1.4.2.0-40jpp.115
>> Hmm... it's probably /not/ your problem, here
> 
> Actually, if Tomcat is crashing, it likely *is* the problem.  gcj has never really made it beyond the toy stage, so that's the first thing to replace.

- From the OP:

> [Sun Mar 29 04:05:33 2009] [error] ajp_read_header: ajp_ilink_receive
> failed
> [Sun Mar 29 04:05:33 2009] [error] (120006)APR does not understand this
> error code: proxy: read response failed from (null) (localhost)

This looks like mod_proxy_ajp complaining, or at least APR, which would
be outside of Tomcat's domain.

- -chris
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Re: ajp_read_header: ajp_ilink_receive failed

Posted by John Oliver <jo...@john-oliver.net>.
On Mon, Apr 06, 2009 at 05:30:49PM -0500, Caldarale, Charles R wrote:
> > From: Christopher Schultz [mailto:chris@christopherschultz.net]
> > Subject: Re: ajp_read_header: ajp_ilink_receive failed
> > 
> > > [root@mda-services ~]# rpm -qa | grep java
> > > java-1.4.2-gcj-compat-devel-1.4.2.0-40jpp.115
> > > gcc-java-4.1.2-42.el5
> > > java-1.4.2-gcj-compat-1.4.2.0-40jpp.115
> > 
> > Hmm... it's probably /not/ your problem, here
> 
> Actually, if Tomcat is crashing, it likely *is* the problem.  gcj has never really made it beyond the toy stage, so that's the first thing to replace.

It is very possible that this gcj stuff is just installed, and is
otherwise collecting dust.

> > I would recommend using Sun's Java. I'd also recommend a newer version
> > (they're on 1.6 these days... 1.4 is a dinosaur).

[root@mda-services ~]# java -version
java version "1.6.0_05"
Java(TM) SE Runtime Environment (build 1.6.0_05-b13)
Java HotSpot(TM) Server VM (build 10.0-b19, mixed mode)

> Definitely.  Make sure when moving up to a real JVM that you remove the Tomcat compatibility package that's used only with 1.4 JVMs.  Since you're using a 3rd-party repackaged Tomcat, that may be difficult to find; on a real Tomcat, the compatibility files are stored in the follow locations:
> 
> $CATALINA_HOME/bin/jmx.jar
> $CATALINA_HOME/common/endorsed/xercesImpl.jar
> $CATALINA_HOME/xml-apis.jar

I don't have any of those files in /var/lib/tomcat5/ which is, I
believe, $CATALINA_HOME (it's referred to as $TOMCAT_HOME, and I suppose
that might be something different, but... )

> While you're upgrading to proper levels of httpd and the JVM, consider installing a real Tomcat from tomcat.apache.org; the 3rd-party ones have files scattered all over, and sometimes change the configuration to the point where behavior is quite different from the standard version.

Using the most recent versions of those would break our support from Red
Hat.  I don't really care about that... I've said we should stop paying
them and use CentOS.  If using more recent versions winds up being the
answer, that would be more ammo for my argument.  But if we can make
things work properly with the supported versions, at least I can always
say, "Blame Red Hat..." :-)

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* John Oliver                             http://www.john-oliver.net/ *
*                                                                     *
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RE: ajp_read_header: ajp_ilink_receive failed

Posted by "Caldarale, Charles R" <Ch...@unisys.com>.
> From: Christopher Schultz [mailto:chris@christopherschultz.net]
> Subject: Re: ajp_read_header: ajp_ilink_receive failed
> 
> > [root@mda-services ~]# rpm -qa | grep java
> > java-1.4.2-gcj-compat-devel-1.4.2.0-40jpp.115
> > gcc-java-4.1.2-42.el5
> > java-1.4.2-gcj-compat-1.4.2.0-40jpp.115
> 
> Hmm... it's probably /not/ your problem, here

Actually, if Tomcat is crashing, it likely *is* the problem.  gcj has never really made it beyond the toy stage, so that's the first thing to replace.
 
> I would recommend using Sun's Java. I'd also recommend a newer version
> (they're on 1.6 these days... 1.4 is a dinosaur).

Definitely.  Make sure when moving up to a real JVM that you remove the Tomcat compatibility package that's used only with 1.4 JVMs.  Since you're using a 3rd-party repackaged Tomcat, that may be difficult to find; on a real Tomcat, the compatibility files are stored in the follow locations:

$CATALINA_HOME/bin/jmx.jar
$CATALINA_HOME/common/endorsed/xercesImpl.jar
$CATALINA_HOME/xml-apis.jar

While you're upgrading to proper levels of httpd and the JVM, consider installing a real Tomcat from tomcat.apache.org; the 3rd-party ones have files scattered all over, and sometimes change the configuration to the point where behavior is quite different from the standard version.

 - Chuck


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Re: ajp_read_header: ajp_ilink_receive failed

Posted by Christopher Schultz <ch...@christopherschultz.net>.
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

John,

On 4/6/2009 5:51 PM, John Oliver wrote:
> RHEL 5.2, httpd-2.2.3-11.el5_1.3, tomcat5-5.5.23-0jpp.7.el5_2.1

2.2.3 is pretty old... any chance of upgrading to 2.2.11? You're nearly
3 years out of sync with the state-of-the-art.

> There is no firewall... Tomcat and httpd are on the same box.

iptables could be interfering, but not likely. Most people don't bother
protecting localhost from itself :)

> I'm not sure how to check the JVM version... this is the first time I've
> ever had to worry about Tomcat and Java stuff, so I'm doing a lot of
> guessing.

$ java -version

> [root@mda-services ~]# rpm -qa | grep java
> java-1.4.2-gcj-compat-devel-1.4.2.0-40jpp.115
> gcc-java-4.1.2-42.el5
> java-1.4.2-gcj-compat-1.4.2.0-40jpp.115

Hmm... it's probably /not/ your problem, here,  but a /lot/ of people
have had problems with the gcj version of Java. Fortunately, you're
taking care of SSL through Apache httpd: that's where I've heard of lots
of incompatibilities and simply incorrect (or very surprising) operation
and/or crashes.

I would recommend using Sun's Java. I'd also recommend a newer version
(they're on 1.6 these days... 1.4 is a dinosaur).

> It seems to work, even with all of these error messages, but this
> setup nwas cobbled together by developers.

So, are you using mod_proxy_ajp? Please post your configuration. I have
had much better luck with mod_jk, but I think that's more due to my
history with it than anything else: I simply have the experience with
mod_jk and not with mod_proxy_ajp.

> I always figure that error messages are there for a reason, and I'm
> better off fixing them.

+1

> Also, Tomcat seems to be pretty unstable and needs to be restarted
> every week or so, and I wouldn't be surprised if these errors have
> something to do with that.

Tomcat itself is super stable. I have never ever had it crash on me.
I've had the JVM crash crash (for different issues) and I've run out of
memory, but Tomcat has never failed me. The most likely reason for
"server instability" is, sadly, your own application. We might be able
to help with that, too.

> I just have no idea how to troubleshoot and tweak this stuff to, 
> hopefully, wind up with a smoothly-running system.

Well, let's get the ajp thing fixed first, then move on to the other
problems. It's midnight in Germany and Croatia. Give Rainer and Mladen a
chance to read this thread and give you some thoughts on the ajp stuff.

- -chris
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Re: ajp_read_header: ajp_ilink_receive failed

Posted by John Oliver <jo...@john-oliver.net>.
On Mon, Apr 06, 2009 at 05:42:21PM -0400, Christopher Schultz wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> John,
> 
> On 4/6/2009 5:15 PM, John Oliver wrote:
> > [Sun Mar 29 04:05:33 2009] [error] ajp_read_header: ajp_ilink_receive
> > failed
> > [Sun Mar 29 04:05:33 2009] [error] (120006)APR does not understand this
> > error code: proxy: read response failed from (null) (localhost)
> > 
> > I get these messages a *lot* in my ssl_error_log  Google isn't helping,
> > and I've had no response on the httpd list, so i'm hoping someone here
> > can steer me in the right direction.
> 
> Tomcat version? JVM version? httpd version? mod_proxy_ajp or mod_jk?
> (looks like mod_proxy_ajp) Firewall involved?

RHEL 5.2, httpd-2.2.3-11.el5_1.3, tomcat5-5.5.23-0jpp.7.el5_2.1  There
is no firewall... Tomcat and httpd are on the same box.

I'm not sure how to check the JVM version... this is the first time I've
ever had to worry about Tomcat and Java stuff, so I'm doing a lot of
guessing.

[root@mda-services ~]# rpm -qa | grep java
java-1.4.2-gcj-compat-devel-1.4.2.0-40jpp.115
gcc-java-4.1.2-42.el5
java-1.4.2-gcj-compat-1.4.2.0-40jpp.115

Basically, the Java applications are the only things we're worried
about.  httpd is used as the front end because of SSL and the Tumbleweed
validator.  It basically hands everything off to Tomcat.  It seems to
work, even with all of these error messages, but this setup nwas cobbled
together by developers.  I always figure that error messages are there
for a reason, and I'm better off fixing them.  Also, Tomcat seems to be
pretty unstable and needs to be restarted every week or so, and I
wouldn't be surprised if these berrors have something to do with that.
I just have no idea how to troubleshoot and tweak this stuff to,
hopefully, wind up with a smoothly-running system.

-- 
***********************************************************************
* John Oliver                             http://www.john-oliver.net/ *
*                                                                     *
***********************************************************************

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Re: ajp_read_header: ajp_ilink_receive failed

Posted by Christopher Schultz <ch...@christopherschultz.net>.
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John,

On 4/6/2009 5:15 PM, John Oliver wrote:
> [Sun Mar 29 04:05:33 2009] [error] ajp_read_header: ajp_ilink_receive
> failed
> [Sun Mar 29 04:05:33 2009] [error] (120006)APR does not understand this
> error code: proxy: read response failed from (null) (localhost)
> 
> I get these messages a *lot* in my ssl_error_log  Google isn't helping,
> and I've had no response on the httpd list, so i'm hoping someone here
> can steer me in the right direction.

Tomcat version? JVM version? httpd version? mod_proxy_ajp or mod_jk?
(looks like mod_proxy_ajp) Firewall involved?

The answers to all of these questions will be very valuable in
determining what the problem might be.

- -chris
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