${tomcat_home} is the root directory of tomcat. Your Tomcat installation should have the following subdirectories:

• ${tomcat_home}\conf - Where you can place various configuration files
• ${tomcat_home}\webapps - Containing example applications
• ${tomcat_home}\bin - Where you place web server plugins

In all the examples in this document ${tomcat_home} will be /var/tomcat3. A worker is defined to be a tomcat process that accepts work from the Apache server.

The mod_jk module was developed and tested on:

• Linux, FreeBSD, AIX, HP-UX, MacOS X, Solaris and should works on major Unixes platforms supporting Apache 1.3 and/or 2.0/2.2
• WinNT4.0-i386 SP4/SP5/SP6a (should be able to work with other service packs), Win2K and WinXP and Win98
• Cygwin (until you have an apache server and autoconf/automake support tools)
• Netware
• i5/OS V5R4 (System I) with Apache HTTP Server 2.0.58. Be sure to have the latest Apache PTF installed.
• Tomcat 3.2.x, Tomcat 3.3.x, Tomcat 4.0.x, Tomcat 4.1.x, Tomcat 5.0.x, Tomcat 5.5.x and Tomcat 6.

The redirector uses ajp12 and ajp13 to send requests to the Tomcat containers. There is also an option to use Tomcat in process, more about the in-process mode can be found in the in process howto.

The ajp12 protocol is only available in Tomcat 3.2.x and 3.3.x.

The ajp12 has been deprecated with Tomcat 3.3.x and you should use instead ajp13 which is the only ajp protocol known by Tomcat 4.x, 5 and 5.5 and Tomcat 6.

Of course Tomcat 3.2.x and 3.3.x also support ajp13 protocol.

Others servlet engines such as jetty have support for ajp13 protocol

In a nutshell a web server is waiting for client HTTP requests. When these requests arrive the server does whatever is needed to serve the requests by providing the necessary content.

Adding a servlet container may somewhat change this behaviour. Now the web server needs also to perform the following:

• Load the servlet container adaptor library and initialise it (prior to serving requests).
• When a request arrives, it needs to check and see if a certain request belongs to a servlet, if so it needs to let the adaptor take the request and handle it.

The adaptor on the other hand needs to know what requests it is going to serve, usually based on some pattern in the request URL, and to where to direct these requests.

Things are even more complex when the user wants to set a configuration that uses virtual hosts, or when they want multiple developers to work on the same web server but on different servlet container JVMs. We will cover these two cases in the advanced sections.

If you've previously configured Apache to use mod_jserv, remove any ApJServMount directives from your httpd.conf.

If you're including tomcat-apache.conf or tomcat.conf, you'll want to remove them as well - they are specific to mod_jserv.

The mod_jserv configuration directives are not compatible with mod_jk !

The auto-configure works only for a single Tomcat running on the same machine where Apache HTTP Server is running. The simplest way to configure Apache HTTP Server to use mod_jk is to turn on the Apache HTTP Server auto-configure setting in Tomcat and put the following include directive at the end of your Apache httpd.conf file (make sure you replace $TOMCAT_HOME with the correct path for your Tomcat installation:

Note: this file may also be generated as $TOMCAT_HOME/conf/auto/mod_jk.conf

This will tell Apache HTTP Server to use directives in the mod_jk.conf-auto file in the Apache configuration. This file is created by enabling the Apache auto-configuration by creating your workers.properties file at $TOMCAT_HOME/conf/jk/workers.properties and adding the listener to the Engine element in the server.xml file as per the following example. Please note that this example is specific to Tomcat 5.x, unlike other sections of this document which also apply to previous Tomcat branches.

Then restart Tomcat and mod_jk.conf should be generated. For more information on this topic, please refer to the API documentation at the Tomcat docs website.

You should use custom configuration when :

• You couldn't use mod_jk.conf-auto since Tomcat engine isn't on the same machine that your Apache web server, ie when you have an Apache in front of a Tomcat Farm.
• Another case for custom configuration is when your Apache is in front of many different Tomcat engines, each one having it's own configuration, a general case in ISP hosting
• Also all Apache webmaster will retain custom configuration to be able to tune the settings to their real needs.

Here is a simple configuration:

JkWorkersFile specify the location where mod_jk will find the workers definitions. JkWorkersFile /etc/httpd/conf/workers.properties

JkLogFile specify the location where mod_jk is going to place its log file.

Since JK 1.2.3 for Apache 2.0/2.2 and JK 1.2.16 for Apache 1.3 this can also be used for piped logging:

JkLogLevel set the log level between :

• info log will contains standard mod_jk activity (default).
• error log will contains also error reports.
• debug log will contains all information on mod_jk activity

info should be your default selection for normal operations.

JkLogStampFormat will configure the date/time format found on mod_jk logfile. Using the strftime() format string it's set by default to "[%a %b %d %H:%M:%S %Y]"

JkRequestLogFormat will configure the format of mod_jk individual request logging. Request logging is configured and enabled on a per virtual host basis. To enable request logging for a virtual host just add a JkRequestLogFormat config. The syntax of the format string is similar to the Apache LogFormat command, here is a list of the available request log format options:

Options	Description
%b	Bytes sent, excluding HTTP headers (CLF format)
%B	Bytes sent, excluding HTTP headers
%H	The request protocol
%m	The request method
%p	The canonical Port of the server serving the request
%q	The query string (prepended with a ? if a query string exists, otherwise an empty string)
%r	First line of request
%s	Request HTTP status code
%T	Request duration, elapsed time to handle request in seconds '.' micro seconds
%U	The URL path requested, not including any query string.
%v	The canonical ServerName of the server serving the request
%V	The server name according to the UseCanonicalName setting
%w	Tomcat worker name
%R	Session route name (available with 1.2.19 and up)

JkRequestLogFormat "%w %V %T"

The directive JkOptions allow you to set many forwarding options which will enable (+) or disable (-) following option. Without any leading signs, options will be enabled.

The four following options +ForwardURIxxx are mutually exclusive. Exactly one of them is required, a negative sign prefix is not allowed with them. The default value is "ForwardURIProxy" since version 1.2.24. It was "ForwardURICompatUnparsed" in version 1.2.23 and "ForwardURICompat" until version 1.2.22. You can turn the default off by switching on one of the other two options. You should leave this at it's default value, unless you have a very good reason to change it.

All options are inherited from the global server to virtual hosts. Options that support enabling (plus options) and disabling (minus options), are inherited in the following way:

options(vhost) = plus_options(global) - minus_options(global) + plus_options(vhost) - minus_options(vhost)

Using JkOptions ForwardURIProxy, the forwarded URI will be partially reencoded after processing inside Apache httpd and before forwarding to Tomcat. This will be compatible with local URL manipulation by mod_rewrite and with URL encoded session ids. JkOptions +ForwardURIProxy

Using JkOptions ForwardURICompatUnparsed, the forwarded URI will be unparsed. It's spec compliant and secure. It will always forward the original request URI, so rewriting URIs with mod_rewrite and then forwarding the rewritten URI will not work. JkOptions +ForwardURICompatUnparsed

Using JkOptions ForwardURICompat, the forwarded URI will be decoded by Apache httpd. Encoded characters will be decoded and explicit path components like ".." will already be resolved. This is less spec compliant and is not safe if you are using prefix JkMount. This option will allow to rewrite URIs with mod_rewrite before forwarding. JkOptions +ForwardURICompat

Using JkOptions ForwardURIEscaped, the forwarded URI will be the encoded form of the URI used by ForwardURICompat. Explicit path components like ".." will already be resolved. This will not work in combination with URL encoded session IDs, but it will allow to rewrite URIs with mod_rewrite before forwarding. JkOptions +ForwardURIEscaped

JkOptions RejectUnsafeURI will block all URLs, which contain percent signs '%' or backslashes '\' after decoding.

Most web apps do not use such URLs. Using the option RejectUnsafeURI, you can block several well known URL encoding attacks. By default, this option is not set.

You can also realise such a check with mod_rewrite, which is more powerful but also slightly more complicated. JkOptions +RejectUnsafeURI

JkOptions ForwardDirectories is used in conjunction with DirectoryIndex directive of Apache web server. As such mod_dir should be available to Apache, statically or dynamically (DSO)

When DirectoryIndex is configured, Apache will create sub-requests for each of the local-url's specified in the directive, to determine if there is a local file that matches (this is done by stat-ing the file).

If ForwardDirectories is set to false (default) and Apache doesn't find any files that match, Apache will serve the content of the directory (if directive Options specifies Indexes for that directory) or a 403 Forbidden response (if directive Options doesn't specify Indexes for that directory).

If ForwarDirectories is set to true and Apache doesn't find any files that match, the request will be forwarded to Tomcat for resolution. This is used in cases when Apache cannot see the index files on the file system for various reasons: Tomcat is running on a different machine, the JSP file has been precompiled etc.

Note that locally visible files will take precedence over the ones visible only to Tomcat (i.e. if Apache can see the file, that's the one that's going to get served). This is important if there is more then one type of file that Tomcat normally serves - for instance Velocity pages and JSP pages. JkOptions +ForwardDirectories

JkOptions ForwardLocalAddress, you ask mod_jk to send the local address, of the Apache web server instead remote client address. This can be used by Tomcat remote address valve for allowing connections only from registered Apache web servers. JkOptions +ForwardLocalAddress

JkOptions FlushPackets, you ask mod_jk to flush Apache's connection buffer after each AJP packet chunk received from Tomcat. This option can have a strong performance penalty for Apache and Tomcat as writes are performed more often than would normally be required (ie: at the end of each response). JkOptions +FlushPackets

JkOptions FlushHeader, you ask mod_jk to flush Apache's connection buffer after the response headers have been received from Tomcat. JkOptions +FlushHeader

JkOptions DisableReuse, you ask mod_jk to close connections immediately after their use. Normally mod_jk uses persistent connections and pools idle connections to reuse them, when new requests have to be sent to Tomcat.

Using this option will have a strong performance penalty for Apache and Tomcat. Use this only as a last resort in case of unfixable network problems. If a firewall between Apache and Tomcat silently kills idle connections, try to use the worker attribute socket_keepalive in combination with an appropriate TCP keepalive value in your OS. JkOptions +DisableReuse

JkOptions ForwardKeySize, you ask mod_jk, when using ajp13, to forward also the SSL Key Size as required by Servlet API 2.3. This flag shouldn't be set when servlet engine is Tomcat 3.2.x (off by default). JkOptions +ForwardKeySize

JkOptions ForwardSSLCertChain, you ask mod_jk, when using ajp13, to forward SSL certificate chain (off by default). Mod_jk only passes the SSL_CLIENT_CERT to the AJP connector. This is not a problem with self-signed certificates or certificates directly signed by the root CA certificate. However, there's a large number of certificates signed by an intermediate CA certificate, where this is a significant problem: A servlet will not have the possibility to validate the client certificate on its own. The bug would be fixed by passing on the SSL_CLIENT_CERT_CHAIN to Tomcat via the AJP connector.
This directive exists only since version 1.2.22. JkOptions +ForwardSSLCertChain

The directive JkEnvVar allows you to forward environment variables from Apache server to Tomcat engine. You can add a default value as a second parameter to the directive. If the default value is not given explicitly, the variable will only be send, if it is set during runtime.
The variables can be retrieved on the Tomcat side as request attributes via request.getAttribute(attributeName). Note that the variables send via JkEnvVar will not be listed in request.getAttributeNames().

The variables are inherited from the global server to virtual hosts. JkEnvVar SSL_CLIENT_V_START undefined

If you have created a custom or local version of mod_jk.conf-local as noted above, you can change settings such as the workers or URL prefix.

JkMount directive assign specific URLs to Tomcat. In general the structure of a JkMount directive is:

You can use the JkMount directive at the top level or inside <VirtualHost> sections of your httpd.conf file.

If the Tomcat Host appBase (webapps) directory is accessible by the Apache web server, Apache can be configured to serve web application context directory static files instead of passing the request to Tomcat.

Caution: For security reasons is is strongly recommended that JkMount is used to pass all requests to Tomcat by default and JkUnMount is used to explicitly exclude static content to be served by httpd. It should also be noted that content served by httpd will bypass any security constraints defined in the application's web.xml.

Use Apache's Alias directive to map a single web application context directory into Apache's document space for a VirtualHost:

Starting with mod_jk 1.2.6 for Apache 2.0/2.2 and 1.2.19 for Apache 1.3, it's possible to exclude some URL/URI from jk processing by setting the env var no-jk, for example with the SetEnvIf Directive.

You could use no-jk env var to fix problem with mod_alias or mod_userdir directive when jk and alias/userdir URLs matches.

Use the mod_jk JkAutoAlias directive to map all web application context directories into Apache's document space.

Attempts to access the WEB-INF or META-INF directories within a web application context or a Web Archive *.war within the Tomcat Host appBase (webapps) directory will fail with an HTTP 403, Access Forbidden

If you encoded all your URLs to contain the session id (;jsessionid=...), and you later decide, you want to move part of the content to Apache httpd, you can tell mod_jk to strip off all session ids from URLs for those requests, that do not get forwarded via mod_jk.

You enable this feature by setting JkStripSession to On. It can be enabled individually for virtual servers. The default value is Off.

To create tomcat-connectors's autoconf script, you will need libtool 1.5.2, automake 1.10 and autoconf 2.59 or newer. The use of more recent versions is encouraged, e.g. for reliable detection of the features of recent version of operating systems.

Those tools will not be required if you are just using a package downloaded from apache.org, they are only required for developers.

To create the configure script just type : ./buildconf.sh

Here's how to use configure to prepare mod_jk for building, just type: ./configure [autoconf arguments] [tomcat-connectors arguments]

You could set CFLAGS and LDFLAGS to add some platform specifics:

If you want to build mod_jk for different version of Apache httpd, like 1.3, 2.0 and 2.2, you need to go through the full build process for each of them. Please note, that httpd 2.0 and 2.2 modules are not compatible. The mod_jk directory used is "apache-2.0" in both cases, but you need to compile separately.

• use configure and indicate the correct Apache httpd apxs location (--with-apxs)
• use make
• copy the resulting mod_jk.so binary from the apache-1.3 or apache-2.0 subdirectory to the Apache httpd modules location.
• make clean (to remove all previously compiled object files)
• Start over with the apxs location for your next Apache httpd version.

Apache related parameters
--with-apxs[=FILE]	FILE is the location of the apxs tool. Default is finding apxs in PATH. It builds a shared Apache module. It detects automatically the Apache version. (2.0/2.2 and 1.3)
--with-apache=DIR	DIR is the path where apache sources are located. The apache sources should have been configured before configuring mod_jk. DIR is something like: /home/apache/apache_1.3.19 It builds a static Apache module.
--enable-EAPI	This parameter is needed when using Apache-1.3 and mod_ssl, otherwise you will get the error message: "this module might crash under EAPI!" when loading mod_jk.so in httpd. Not needed when --with-apxs has been used
--enable-prefork	In case you build mod_jk for a multi-threaded Apache httpd 2.0/2.2 MPM (Multi-Processing Module), some areas of mod_jk code need to be synchronised to make it thread-safe. Because configure can not easily detect, whether your are using a multi-threaded MPM, mod_jk by default is always build thread-safe for Apache httpd 2.0/2.2. If you are sure, that your MPM is not multi-threaded, you can use "--enable-prefork" to force the removal of the synchronisation code (thus increasing performance a bit). For instance, the prefork MPM is not multi-threaded. For Apache httpd 1.3 this flag will be set automatically.
--disable-trace	When using log level "trace", mod_jk traces a lot of function calls with "enter" and "exit" log messages. Even if the log level is not "trace", comparing the log levels to decide about logging has some performance impact. If you use "--disable-trace", then the trace log code doesn't get compiled into the module binary and you might save some cycles during execution. Even with "--disable-trace" logging debug messages with debug log level will still be possible.
--enable-api-compatibility	Only use httpd API functions available in all httpd production releases of the chosen major httpd release branch. This improves binary compatibility of module builds with httpd releases older than the release against mod_jk is build (only between minor httpd versions).
--enable-flock	In case the operating system supports flock system call use this flag to enable this faster locks that are implemented as system call instead emulated by GNU C library. However those locks does not work on NFS mounted volumes, so you can use "--enable-flock" during compile time to force the flocks() calls.

DEPRECATED: JNI related parameters
--enable-jni	Build the JNI worker and so the build process will require some information about your Java Environment
--with-java-home=DIR	DIR is the patch to the JDK root directory. Something like: /opt/java/jdk12
--with-os-type=SUBDIR	SUBDIR is the os-type subdirectory, configure should guess it correctly.
--with-arch-type=SUBDIR	SUBDIR is the arch subdirectory, configure should guess it correctly.
--with-java-platform=VAL	VAL is the Java platform 1 is 1.1.x and 2 is for 1.2 and higher, configure should guess it correctly.

The enable-jk=share and enable-jk=static are not supported. --with-mod_jk only allow static linking of mod_jk.

The --enable-shared=jk is also working and builds a dso file.