FAQ

The primary mechanism for support is through the JK documentation included in the doc directory. Documentation is also available on the Apache Jakarta web site devoted to the Jakarta Tomcat Connectors Project For additional help, the best resource is the Tomcat Users Discussion list. You should start by searching the mail list archive before you post questions to the list. If you are unable to locate the answer to your question in the archive, you can post questions about JK to the user list for assistance. Make sure that you include the version of your Webserver, that you are using as well as the platform you are running on and go here to determine how to subscribe to tomcat mailing list.

Now that JK moved to the jakarta-tomcat-connectors repository, the source and binaries for JK are present in the jakarta-tomcat-connectors directory

JK is a project covering web-servers to Tomcat connectors, whereas mod_jk is the Apache module developped in JK.

Domino webserver support is implemented on JK, using a redirector called dsapi redirector .

IIS webserver support is implemented on JK, using a redirector called isapi redirector .

Netscape/iPlanet webserver webserver support is implemented on JK, using a redirector called nsapi redirector .

For JK 2.0.x the config tomcat and config webserver documents have considerably more in-depth information. It's worth a look. You could also try searching the mailing list archives for "JK" or look at the source.

Ajp13 is a newer protocol, it's faster, and it works better with SSL. You almost certainly want to use it now that ajp12 is deprecated.

Also ajp13 is supported by all Apache Tomcat including 3.2.x , 3.3.x, 4.0.x, 4.1.x and the new tomcat 5.

Ajp13 use persistant connections where the traffic could be null if there is no request to be sent to Tomcat. Firewall used to drop inactive connections and will make your WebServer and Tomcat think the connection is valid.

Starting with JK 1.2.0, a socket_keepalive property as been added to ajp13 settings, and you should take a look at it in Workers HowTo .

Under heavy load, Apache WebServer create many childs to handle the load, which will in turn create many connections to Tomcat to forward the requests they should handle. Apache WebServer will normally kill the childs/threads when the load decrease. But if the load is still there and even if only Apache handle the requests, ie static contents, the childs are kept and with them the ajp13 connections, even if they are no more used.

Since JK 1.2.0, cache_timeout and socket_timeout properties as been added to close connections after some time of inactivity, for more informations refer to Workers HowTo .

The Ajp13 protocol keeps an open socket between Tomcat and Apache. Release of mod_jk present in J-T-C handle the network failure. But with previous release of mod_jk, you may have to restart Apache as well.

Many versions of Apache use of modified API, known at Extended API, developped for use with the mod_ssl module .

For example, Apache present in certains recent Linux distributions include the mod_ssl module.

You should use mod_jk.so-noeapi only for 'Standard Apache' (ie without mod_ssl).

It's wise to avoid using EAPI modules on STD API Apache or to use standard API modules on EAPI Apache. Allways be sure to have the mod_jk.so witch match your version of Apache

It's related to Apache EAPI, the message 'mod_jk.so is garbled - perhaps this is not an Apache module DSO ?' just told you, that your're trying to install a mod_jk.so DSO module that was compiled on an Apache using EAPI, like apache-mod_ssl or apache from Redhat distro 6.2/7.0 but your system use the standard apache with normal API.

Also related to EAPI, the message '[warn] Loaded DSO /usr/lib/apache/mod_jk.so uses plain Apache 1.3 API, this module might crash under EAPI! (please recompile it with -DEAPI)', the mod_jk.so was compiled under normal Apache with standard API and you try to install the module on an Apache using EAPI.

APXS is a Perl script that is created when you build the Apache web server from source. Chances are that if you are getting these errors and you obtained Apache as a binary distribution, that APXS is not configured correctly for your system. Your best bet is to get the Apache source from http://httpd.apache.org and build it yourself. Use the following for a basic build (read the Apache docs for other options):



[user@host] ~ $ 
cd /usr/local/src



[user@host] ~ $ 
gzip -dc apache_1.3.19.tar.gz|tar xvf -



[user@host] ~ $ 
cd apache_1.3.19



[user@host] ~ $ 
./configure --prefix=/usr/local/apache \



[user@host] ~ $ 
            --enable-module=most \



[user@host] ~ $ 
            --enable-shared=max



[user@host] ~ $ 
make



[user@host] ~ $ 
make install

Note: The above steps assume that you downloaded the Apache source and placed it in your /usr/local/src directory.

Since Apache 2.0 API still change often, the Apache 2.0 teams decide to put in headers of compiled modules the Apache 2.0 version used to compile the module. This check is called Magic Module Number bump.

At start time Apache 2.0 check that version in modules headers and stop if it detect that a module was compiled for another Apache 2.0 version. As such you should allways use modules compiled for the same Apache 2.0 version. This check may be removed if the future.

JNI support require a multi-threaded environment which is not the general case for Apache 1.3. You should verify if Apache 1.3 has been build with thread support and if not you could add the the pthreads library to your httpd.conf file.

Also keep in mind that JNI is suited for multi-threaded servers and you should consider upgrading to Apache 2.0 to support JNI.

Under Linux, you should set some environment variables BEFORE launching your Apache server :

Also some Linux distributions have enabled a GLIBC feature called 'floating stacks' which may not works with kernel less than 2.4.10 on SMP machines. You should disable floating stacks by exporting an environment variable :

You could have to update your service scripts, ie /etc/rc.d/init.d/httpd , to set these env vars before your httpd server starts.