Been stuck with this one for a few days. Will try to provide as much information as possible, but please feel free to ask for extra detail.

I have 2 VMs behind a NAT, 192.168.0.100 and 192.168.0.102, both running Ubuntu 11.04 x64. The first one is mapped to the exterior and is our webserver, has one Apache/2.2.17 install with several vhosts to serve static content, and there's also mod_jk for load balancing. The second one has a tomcat 7 install with several J2EE REST webservices but no apache - requests are expected to be passed directly from .100 apache to .102 tomcat. It is my intention to prepare a tomcat clustered environment.

My problem: Requests reach to 192.168.0.100 with no trouble whatsoever, but then take about... 100 seconds for data to actually arrive to .102 - by that time apache has already timeouted, but tomcat receives and processes the request pretty normally. This happens both when using mod_jk, mod_proxy, or mod_ajp_proxy. No idea why, since there are no firewalls in either of the machines, both are pingable - more than that, there are NFS shares active working like a charm - and a mod_proxy experience shown that requests originating directly from .100 are processed normally.

Also, to add insult to injury, a similar environment is set up at our office network. Everything works perfectly. -_- The only difference? We have no ip translation at the office and do everything by internal addresses - dunno if that's relevant in any way.

Some configs:

Apache vhost:

<VirtualHost *:80>
    ServerAdmin webmaster@localhost
    DocumentRoot /var/www/
    ServerName www.example.com

    ProxyRequests Off
    <Proxy *>
            Options Indexes FollowSymLinks MultiViews
            AllowOverride all
            Order allow,deny
            allow from all
    </Proxy>

    ProxyPass /bork http://192.168.0.102:8080/bork
    ProxyPassReverse /bork http://192.168.0.102:8080/bork
    LogLevel debug

    CustomLog ${APACHE_LOG_DIR}/api_access.log combined
    ErrorLog ${APACHE_LOG_DIR}/api_error.log
</VirtualHost>

Tomcat connectors

<Connector port="8080" protocol="HTTP/1.1"
           connectionTimeout="20000"
           redirectPort="8443" />
<Connector port="8009"
    enableLookups="false"
    redirectPort="8443"
    protocol="AJP/1.3"
/>

And a debug log from apache, from a test using mod_proxy_ajp. The behavior is pretty much the same in mod_proxy, at least regarding the delay. Please note that tomcat eventually receives and processes the request, more or less when the log starts being updated again:

[Sun May 06 14:40:33 2012] [debug] proxy_util.c(1506): [client 188.81.234.2] proxy: ajp: found worker ajp://192.168.0.102:8008/bork for ajp://192.168.0.102:8008/bork/SSOIdentityProviderSoap
[Sun May 06 14:40:33 2012] [debug] mod_proxy.c(1015): Running scheme ajp handler (attempt 0)
[Sun May 06 14:40:33 2012] [debug] mod_proxy_ajp.c(661): proxy: AJP: serving URL ajp://192.168.0.102:8008/bork/SSOIdentityProviderSoap
[Sun May 06 14:40:33 2012] [debug] proxy_util.c(2011): proxy: AJP: has acquired connection for (192.168.0.102)
[Sun May 06 14:40:33 2012] [debug] proxy_util.c(2067): proxy: connecting ajp://192.168.0.102:8008/bork/SSOIdentityProviderSoap to 192.168.0.102:8008
[Sun May 06 14:40:33 2012] [debug] proxy_util.c(2193): proxy: connected /bork/SSOIdentityProviderSoap to 192.168.0.102:8008
[Sun May 06 14:40:33 2012] [debug] proxy_util.c(2444): proxy: AJP: fam 2 socket created to connect to 192.168.0.102
[Sun May 06 14:40:33 2012] [debug] ajp_header.c(224): Into ajp_marshal_into_msgb
[Sun May 06 14:40:33 2012] [debug] ajp_header.c(290): ajp_marshal_into_msgb: Header[0] [Accept-Encoding] = [gzip,deflate]
[Sun May 06 14:40:33 2012] [debug] ajp_header.c(290): ajp_marshal_into_msgb: Header[1] [Content-Type] = [text/xml;charset=UTF-8]
[Sun May 06 14:40:33 2012] [debug] ajp_header.c(290): ajp_marshal_into_msgb: Header[2] [SOAPAction] = [""]
[Sun May 06 14:40:33 2012] [debug] ajp_header.c(290): ajp_marshal_into_msgb: Header[3] [User-Agent] = [Jakarta Commons-HttpClient/3.1]
[Sun May 06 14:40:33 2012] [debug] ajp_header.c(290): ajp_marshal_into_msgb: Header[4] [Host] = [www.example.com]
[Sun May 06 14:40:33 2012] [debug] ajp_header.c(290): ajp_marshal_into_msgb: Header[5] [Content-Length] = [520]
[Sun May 06 14:40:33 2012] [debug] ajp_header.c(450): ajp_marshal_into_msgb: Done
[Sun May 06 14:40:33 2012] [debug] mod_proxy_ajp.c(267): proxy: APR_BUCKET_IS_EOS
[Sun May 06 14:40:33 2012] [debug] mod_proxy_ajp.c(272): proxy: data to read (max 8186 at 4)
[Sun May 06 14:40:33 2012] [debug] mod_proxy_ajp.c(287): proxy: got 520 bytes of data
[Sun May 06 14:40:33 2012] [debug] ajp_header.c(687): ajp_read_header: ajp_ilink_received 06
[Sun May 06 14:40:33 2012] [debug] ajp_header.c(697): ajp_parse_type: got 06
[Sun May 06 14:40:37 2012] [debug] proxy_util.c(1818): proxy: grabbed scoreboard slot 2 in child 5916 for worker ajp://192.168.0.100:8008/coding
[Sun May 06 14:40:37 2012] [debug] proxy_util.c(1837): proxy: worker ajp://192.168.0.100:8008/coding already initialized
[Sun May 06 14:40:37 2012] [debug] proxy_util.c(1934): proxy: initialized single connection worker 2 in child 5916 for (192.168.0.100)
[Sun May 06 14:40:37 2012] [debug] proxy_util.c(1818): proxy: grabbed scoreboard slot 3 in child 5916 for worker http://192.168.0.102:8080
[Sun May 06 14:40:37 2012] [debug] proxy_util.c(1837): proxy: worker http://192.168.0.102:8080 already initialized
[Sun May 06 14:40:37 2012] [debug] proxy_util.c(1934): proxy: initialized single connection worker 3 in child 5916 for (192.168.0.102)
[Sun May 06 14:40:37 2012] [debug] proxy_util.c(1818): proxy: grabbed scoreboard slot 4 in child 5916 for worker ajp://192.168.0.102:8008/bork
[Sun May 06 14:40:37 2012] [debug] proxy_util.c(1837): proxy: worker ajp://192.168.0.102:8008/bork already initialized
[Sun May 06 14:40:37 2012] [debug] proxy_util.c(1934): proxy: initialized single connection worker 4 in child 5916 for (192.168.0.102)
[Sun May 06 14:40:38 2012] [debug] proxy_util.c(1934): proxy: initialized single connection worker 2 in child 5918 for (192.168.0.100)
[Sun May 06 14:40:38 2012] [debug] proxy_util.c(1818): proxy: grabbed scoreboard slot 3 in child 5918 for worker http://192.168.0.102:8080
[Sun May 06 14:40:38 2012] [debug] proxy_util.c(1837): proxy: worker http://192.168.0.102:8080 already initialized
[Sun May 06 14:40:38 2012] [debug] proxy_util.c(1934): proxy: initialized single connection worker 3 in child 5918 for (192.168.0.102)
[Sun May 06 14:40:38 2012] [debug] proxy_util.c(1818): proxy: grabbed scoreboard slot 4 in child 5918 for worker ajp://192.168.0.102:8008/bork
[Sun May 06 14:40:38 2012] [debug] proxy_util.c(1837): proxy: worker ajp://192.168.0.102:8008/bork already initialized
[Sun May 06 14:40:38 2012] [debug] proxy_util.c(1934): proxy: initialized single connection worker 4 in child 5918 for (192.168.0.102)
[Sun May 06 14:40:38 2012] [debug] proxy_util.c(1818): proxy: grabbed scoreboard slot 2 in child 5917 for worker ajp://192.168.0.100:8008/coding
[Sun May 06 14:40:38 2012] [debug] proxy_util.c(1837): proxy: worker ajp://192.168.0.100:8008/coding already initialized
[Sun May 06 14:40:38 2012] [debug] proxy_util.c(1934): proxy: initialized single connection worker 2 in child 5917 for (192.168.0.100)
[Sun May 06 14:40:38 2012] [debug] proxy_util.c(1818): proxy: grabbed scoreboard slot 3 in child 5917 for worker http://192.168.0.102:8080
[Sun May 06 14:40:38 2012] [debug] proxy_util.c(1837): proxy: worker http://192.168.0.102:8080 already initialized
[Sun May 06 14:40:38 2012] [debug] proxy_util.c(1934): proxy: initialized single connection worker 3 in child 5917 for (192.168.0.102)
[Sun May 06 14:40:38 2012] [debug] proxy_util.c(1818): proxy: grabbed scoreboard slot 4 in child 5917 for worker ajp://192.168.0.102:8008/bork
[Sun May 06 14:40:38 2012] [debug] proxy_util.c(1837): proxy: worker ajp://192.168.0.102:8008/bork already initialized
[Sun May 06 14:40:38 2012] [debug] proxy_util.c(1934): proxy: initialized single connection worker 4 in child 5917 for (192.168.0.102)
[Sun May 06 14:42:09 2012] [debug] ajp_header.c(687): ajp_read_header: ajp_ilink_received 04
[Sun May 06 14:42:09 2012] [debug] ajp_header.c(697): ajp_parse_type: got 04
[Sun May 06 14:42:09 2012] [debug] ajp_header.c(516): ajp_unmarshal_response: status = 200
[Sun May 06 14:42:09 2012] [debug] ajp_header.c(537): ajp_unmarshal_response: Number of headers is = 1
[Sun May 06 14:42:09 2012] [debug] ajp_header.c(599): ajp_unmarshal_response: Header[0]     [Content-Type] = [text/xml;charset=utf-8]
[Sun May 06 14:42:09 2012] [debug] ajp_header.c(609): ajp_unmarshal_response: ap_set_content_type done
[Sun May 06 14:42:09 2012] [debug] ajp_header.c(687): ajp_read_header: ajp_ilink_received 03
[Sun May 06 14:42:09 2012] [debug] ajp_header.c(697): ajp_parse_type: got 03
[Sun May 06 14:42:09 2012] [debug] ajp_header.c(687): ajp_read_header: ajp_ilink_received 03
[Sun May 06 14:42:09 2012] [debug] ajp_header.c(697): ajp_parse_type: got 03
[Sun May 06 14:42:09 2012] [debug] ajp_header.c(687): ajp_read_header: ajp_ilink_received 05
[Sun May 06 14:42:09 2012] [debug] ajp_header.c(697): ajp_parse_type: got 05
[Sun May 06 14:42:09 2012] [debug] mod_deflate.c(615): [client 188.81.234.2] Zlib: Compressed 447 to 255 : URL /bork/SSOIdentityProviderSoap
[Sun May 06 14:42:09 2012] [debug] mod_proxy_ajp.c(570): proxy: got response from (null) (192.168.0.102)
[Sun May 06 14:42:09 2012] [debug] proxy_util.c(2029): proxy: AJP: has released connection for (192.168.0.102)
[Sun May 06 14:42:09 2012] [info] [client 188.81.234.2] Request body read timeout

Was wondering if any one could provide some advice, perhaps even point out any hideous, horrible configuration error? thanks in advance!