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The Apache Tomcat Connectors - Web Server HowTo

ISAPI redirector for Micrsoft IIS HowTo

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Introduction

This document explains how to set up the ISAPI redirector for IIS to cooperate with Tomcat.

Normally IIS can not execute Servlets and Java Server Pages (JSPs), configuring IIS to use the ISAPI redirector plugin will let IIS send servlet and JSP requests to Tomcat (and this way, serve them to clients).

It is recommended that you also read the Workers HowTo document to learn how to setup the working entities between your web server and Tomcat Engines. For more detailed configuration information consult the Reference Guide for workers.properties, uriworkermap and IIS.

Document Conventions and Assumptions

${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 c:\tomcat. A worker is defined to be a tomcat process that accepts work from the IIS server.

Supported Configuration

The IIS to Tomcat redirector works for:

  • WinNT4.0-i386 SP4/SP5/SP6a (should be able to work with other service packs), Win98, WinXP, Win2K, and probably also Win2K3, Vista and Windows 7.
  • IIS4.0 and PWS4.0, IIS 5 to IIS 7.
  • Tomcat 3.2 to Tomcat 8.

The mod_jk module uses the AJP protocol to send requests to the Tomcat containers. The AJP version typically used is ajp13.

IIS 5 and 6 Notes

There are extra steps you need to take for configuring Tomcat with IIS 5 and 6. Please see the appropriate links from Tomcat Useful Links.

IIS 7 notes

There is a known bug in IIS that may result in incomplete log messages. See bug 45769 for further details.

64 Bit notes

In a 64 Bit environment - at least for IIS 7 - the used IIS Application Pool should have "Enable 32-bit Applications" set to "False". Otherwise the redirector will not be called and returns an http code 404. If you think, the 32bit version of isapi_redirect.dll would do the job instead, you will get an http code 500, because the library is not loadable into a 64 Bit IIS.

Who supports AJP protocols?

Tomcat supports ajp13 since Tomcat 3.2. Others servlet engines such as Jetty or JBoss also support the ajp13 protocol

The ajp12 protocol has been deprecated and you should no longer use it. The ajp14 protocol is considered experimental.

How does it work ?

  1. The ISAPI redirector is a Microsoft IIS plugin (filter + extension). IIS loads the redirector plugin and calls its filter function for each in-coming request.
  2. The filter then tests the request URL against a list of URI-paths held inside uriworkermap.properties, If the current request matches one of the entries in the list of URI-paths, the filter transfers the request to the extension.
  3. The extension collects the request parameters and forwards them to the appropriate worker using the defined protocol like ajp13.
  4. The extension collects the response from the worker and returns it to the browser.

Installation

A pre-built version of the ISAPI redirector plugin, isapi_redirect.dll, is available under the win32/i386 directory of the Tomcat Connectors distribution. You can also build a copy locally from the Tomcat Connectors source distribution. The ISAPI redirector requires three entities:

  • isapi_redirect.dll - The ISAPI redirector for Microsoft IIS plugin, either obtain a pre-built DLL or build it yourself (see the build section).
  • workers.properties - A file that describes the host(s) and port(s) used by the workers (Tomcat processes). A sample workers.properties can be found under the conf directory.
  • uriworkermap.properties - A file that maps URL-Path patterns to workers. A sample uriworkermap.properties can be found under the conf directory as well.

The installation includes the following parts:

  • Configuring the ISAPI redirector with a default /examples context and checking that you can serve servlets with IIS.
  • Adding more contexts to the configuration.

Configuring the ISAPI Redirector

In this document I will assume that isapi_redirect.dll is placed in c:\tomcat\bin\win32\i386\isapi_redirect.dll and that the properties files which you created are in c:\tomcat\conf.

  1. In the registry, create a new registry key named "HKEY_LOCAL_MACHINE\SOFTWARE\Apache Software Foundation\Jakarta Isapi Redirector\1.0"
  2. Add a string value with the name extension_uri and a value of /jakarta/isapi_redirect.dll
  3. Add a string value with the name log_file and a value pointing to where you want your log file to be (for example c:\tomcat\logs\isapi.log).
  4. Add a string value with the name log_level and a value for your log level (can be debug, info, error or emerg).
  5. Add a string value with the name worker_file and a value which is the full path to your workers.properties file (for example c:\tomcat\conf\workers.properties)
  6. Add a string value with the name worker_mount_file and a value which is the full path to your uriworkermap.properties file (for example c:\tomcat\conf\uriworkermap.properties)
  7. Using the IIS management console, add a new virtual directory to your IIS/PWS web site. The name of the virtual directory must be jakarta. Its physical path should be the directory where you placed isapi_redirect.dll (in our example it is c:\tomcat\bin\win32\i386). While creating this new virtual directory assign it with execute access.
  8. Using the IIS management console, add isapi_redirect.dll as a filter in your IIS/PWS web site. The name of the filter should reflect its task (I use the name tomcat), its executable must be our c:\tomcat\bin\win32\i386\isapi_redirect.dll. For PWS, you'll need to use regedit and add/edit the "Filter DLLs" key under HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\W3SVC\Parameters. This key contains a "," separated list of dlls (full paths) - you need to insert the full path to isapi_redirect.dll.
  9. If you're using IIS 6.0 you must also do the following:
    Using the IIS management console, add the ISAPI Redirector to the Web Service Extensions.
    1. Right-click on Web Service Extensions and choose Add a new Web Service Extension.
    2. Enter tomcat for the Extension Name.
    3. Add the isapi_redirect.dll to the required files.
    4. Check the Set extension status to Allowed.
    5. Click on OK.
  10. Restart IIS (stop + start the IIS service), make sure that the tomcat filter is marked with a green up-pointing arrow. Under Win98 you may need to cd WINDOWS\SYSTEM\inetsrv and type PWS /stop ( the DLL and log files are locked - even if you click the stop button, PWS will still keep the DLLs in memory. ). Type pws to start it again.

That's all, you should now start Tomcat and ask IIS to serve you the /examples context. Try http://localhost/examples/ for example and execute some of the Servlet or JSP examples.

If this does not work successfully, refer to the Troubleshooting section below for help on correcting the problem.

Adding additional Contexts

The examples context is useful for verifying your installation, but you will also need to add your own contexts. Adding a new context requires two operations:

  1. Adding the context to Tomcat (I am not going to talk about this).
  2. Adding the context to the ISAPI redirector.

Adding a context to the ISAPI redirector is simple, all you need to do is to edit your uriworkermap.properties and to add a line that looks like:

  /context/*=worker_name

Workers and their name are defined in workers.properties, by default workers.properties comes with a single pre-configured worker named "defworker" so you can use it. As an example, if you want to add a context named "shop", the line that you should add to uriworkermap.properties will be:

  /shop/*=defworker
After saving uriworkermap.properties restart IIS and it will serve the new context.

The above should be all you need for IIS to pass through to Tomcat any request for any URI which corresponds to a Tomcat context (webapp).

Advanced Context Configuration

If your webiste is very busy (more than 100 requests/second, or more than 100 simultaneous client connections), it might sometimes be desirable to have IIS serve static content (html, gif, jpeg etc.) directly, even if these files are part of a context served by Tomcat. Allowing IIS to serve such files directly may avoid the small overhead consisting of passing the request to Tomcat via the redirector, and may free up Tomcat somewhat, by using it only to process requests that only Tomcat can handle (e.g. requests to JSP pages and java servlets).

For example, consider the html and gif files in the examples context: you could serve these files directly with IIS; there is no need to serve them from the Tomcat process.

However, you should be very careful when you implement the following configuration style, because by doing so you are in fact providing a "back-door" to IIS, and allowing it to serve files out of a Tomcat context without Tomcat's knowledge, thus bypassing any security restrictions which Tomcat itself and the Tomcat context (webapp) may place on those files.

Making IIS serve static files that are part of the Tomcat contexts requires the following:

  1. Configuring IIS to know about the Tomcat contexts
  2. Configuring the redirector to leave the static files for IIS

Adding a Tomcat context to IIS requires the addition of a new IIS virtual directory that covers the Tomcat context. For example adding a /example IIS virtual directory that covers the c:\tomcat\webapps\examples directory.

Configuring the redirector is somewhat harder, you will need to specify the exact URL-Path pattern(s) which you want Tomcat to handle (usually only JSP files and servlets). This requires a change to the uriworkermap.properties:

  For the examples context it requires to replace the following line
  /examples/*=defworker
  with the following two lines
  /examples/*.jsp=defworker
  /examples/servlet/*=defworker

As you can see the second configuration is more explicit, it actually instruct the redirector to redirect only requests to resources under /examples/servlet/ and resources under /examples/ whose name ends with .jsp.

You can even be more explicit and provide lines such as:

  /example/servlets/chat=defworker

that instructs the redirector to redirect all requests whose URL-path matches the leading string "/example/servlets/chat" to the worker named defworker.

Protecting the content of your Tomcat contexts

Once again, be aware that by allowing IIS to access the content of your Tomcat context directly, you are potentially bypassing Tomcat's protection of that content. You should thus make sure to protect this content at the IIS level if needed, by using the corresponding IIS management console functions.

In particular, each servlet application (context) has a special directory named WEB-INF, which contains sensitive configuration data and Java classes, and which should always be kept hidden from web users. Using the IIS management console it is possible to protect the WEB-INF directory from user access, but considering that this is a general requirement, and considering that it is easy to forget to implement this protection at the IIS level, the ISAPI redirector plugin does it automatically for you, and it will reject any request which contains WEB-INF in its URL path. It will also reject any request which contains META-INF in its URL path.

Advanced Worker Configuration

Sometimes you may want to serve different contexts with different Tomcat processes (for example to spread the load among different machines). To achieve such a goal you will need to define several workers and assign each context to its own worker.

Defining additional workers is done in the workers.properties file. This file includes two types of entries:

  # An entry that lists all the workers defined
  worker.list=worker1, worker2
  # Entries that define the host and port associated with each of these workers
  worker.worker1.host=localhost
  worker.worker1.port=8009
  worker.worker1.type=ajp13
  worker.worker2.host=otherhost
  worker.worker2.port=8009
  worker.worker2.type=ajp13

The above example defined two workers, now we can use these workers to serve two different contexts each with its own worker:

  example uriworkermap.properties fragment
  /examples/*=worker1
  /webpages/*=worker2

As you can see the examples context is served by worker1 while the webpages context is served by worker2.

More information on using and configuring workers in the Workers HowTo and in the worker.properties configuration reference.

Building the ISAPI redirector

The redirector was developed using Microsoft Visual C++, so having Visual Studio installed is a prerequisite if you want to perform your own build.

You can build the source using the IDE GUI, or using a pure commandline build based on nmake. The IDE build currently only supports building 32 Bit binaries. The nmake builds are available for 32 Bit, 64 Bit and Itanium binaries.

The common steps for all build procedures are:

  • Set up your build environment for 32 Bits or 64 Bits. The IDE build only supports 32 Bits.
  • Download the sources as a zip file and unpack it.
  • Change directory to the ISAPI redirector source directory.

Set up 32 or 64 Bit build environment
c:\>setenv /Release /X86
or (not available for IDE build)
c:\>setenv /Release /X64
Download tomcat-connectors-xxx-src.zip from
https://tomcat.apache.org/download-connectors.cgi
and unpack it
c:\>unzip tomcat-connectors-xxx-src.zip
Change directory to the ISAPI redirector source directory
c:\>cd tomcat-connectors-xxx-src\native\iis

The steps for an IDE build are then:

  • Start Visual Studio using "start isapi.dsw"
  • During IDE startup choose "Yes" in all conversion popups.
  • Next choose "Debug" or "Release" in the Configuration dropdown.
  • Finally choose "Build Solution" in the "Build" menu.
The resulting file isapi_redirect.dll (and the debug symbol file isapi_redirect.pdb) is located in the "Debug" resp. "Release" sub directory depending on the build Configuration chosen. As an intermediate step the build first creates a static PCRE library named pcre.lib in the sub directory "pcre/LibD" resp. "pcre/LibR".

Alternatively the steps for an nmake commandline build are:

  • Issue "nmake -f Makefile.x86" for a 32 Bit build, or
  • Issue "nmake -f Makefile.amd64" for a 64 Bit build, or
  • Issue "nmake -f Makefile.i64" for a Itanium Bit build
The resulting file isapi_redirect.dll (and the debug symbol file isapi_redirect.pdb) is located in the "Release_x86" resp. "Release_amd64" resp. "Release_ia64" sub directory. As an intermediate step the build first creates a static PCRE library named pcre.lib in the sub directory "pcre/Release_x86" resp. "pcre/Release_amd64" resp. "pcre/Release_ia64.

Troubleshooting

It is easy to have the ISAPI redirector not work the first time you try to install it.

If this happens to you, here are some steps to follow to try to correct the problem.

These steps aren't guaranteed to cover all possible problems, but they should help find the typical mistakes.

If you make any corrections during these steps, restart the IIS service as described above in the last step of the installation, then retry the step.

To enable error tracking, make sure web site activity is being logged. For PWS 4.0 make sure "Save Web Site Activity Log" is checked in the Advanced Options of the Personal Web Manager.

Note: These steps assume your worker_mount_file setting points to an unmodified copy of the uriworkermap.properties file.
Results may be misleading if worker_mount_file points to a modified uriworkermap.properties or the uriworkermap.properties-auto file.
It is also assumed that the "/examples" context works correctly if you access Tomcat directly.

Win98

Start the IIS service and Tomcat.

Check for the presence of the ISAPI redirector log file you specified in the log_file setting. If not found, verify the following:

  • Check the "Filter DLLs" setting in the "HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\W3SVC\Parameters" key and make sure the path is correct.
  • Check the spelling of the "HKEY_LOCAL_MACHINE\SOFTWARE\Apache Software Foundation\Jakarta Isapi Redirector\1.0" key. Case isn't important, but an incorrect letter will prevent the isapi_redirect.dll from finding its registry settings.
  • Check the log_file setting for typos, name and data. Also insure the directory in which the log file will appear already exists.
  • If the above are set correctly, the ISAPI redirector should be able to create the log file.

Invoke the URL http://localhost/examples/ in your browser. Case is important in Tomcat. The characters following "localhost" in the URL must be lower case. If the page fails to appear, stop the IIS service (required to view the IIS log file). Then examine the last line in the IIS log file in found in SYSTEM/LogFiles/W3SVC1:

If the last line contains:

  GET "/examples/ HTTP/1.1" 404

then the ISAPI redirector is not recognising that it should be handling requests for the "/examples" context. Check the following:

  • Check the extension_uri name for typos.
  • Check the worker_file setting for typos, name and data.
  • Check the worker_mount_file setting typos, name and data.
  • If these are set correctly, the ISAPI redirector should recognise that it should handle requests for the "/examples" context.

If the last line contains something like:

  GET "/jakarta/isapi_redirect.dll HTTP1.1"

then the ISAPI redirector is recognising that it should handle the request, but is not successful at getting Tomcat to service the request.

You should check the HTTP error code following GET "/...":

  Error 404
  GET "/..." 404
  • Make sure you entered the URL correctly.
  • Make sure the virtual directory created was called "jakarta". It should display in Personal Web Manager as "/jakarta" (without the quotes).
  • Make sure the extension_uri data begins with "/jakarta/" (without the quotes).
  Error 500
  GET "/..." 500
  • Make sure that "isapi_redirect.dll" follows "/jakarta/" in the extension_uri setting.
  • Check the workers.properties file and make sure the port setting for worker.ajp13.port is the same as the port specified in the server.xml for the "AJP" connector.
  Error 200 or 403
  GET "/..." 200
  GET "/..." 403
  • Make sure you have checked Execute Access for the jakarta virtual directory in the Advanced Options of the Personal Web Manager.

If the above settings are correct, the index.html page should appear in your browser. You should also be able to click the links to execute some Servlet or JSP examples.

WinNT/Win2K/WinXP

Start the World Wide Web Publishing Service and Tomcat.

Check for the presence of the ISAPI redirector log file you specified in the log_file setting. If not found, check the following:

  • Check the "executable" you set for the filter in the IIS Management Console and make sure the path is correct.
  • Check the spelling of the "HKEY_LOCAL_MACHINE\SOFTWARE\Apache Software Foundation\Jakarta Isapi Redirector\1.0" key. Case isn't important, but an incorrect letter will prevent the isapi_redirect.dll from finding its registry settings.
  • Check the log_file setting for typos, name and data. Also insure the directory in which the log file will appear already exists.
  • If the above are set correctly, the ISAPI redirector should be able to create the log file.

Check the tomcat filter you added and make sure its status shows a green upward-pointing arrow. If not, check the following:

  • Check the worker_file setting for typos, name and data.
  • Check the worker_mount_file setting typos, name and data.
  • If the above are set correctly, the green upward-pointing arrow should appear, even if the other settings are wrong.

Invoke the URL http://localhost/examples/ in your browser. Case is important in Tomcat. The characters following "localhost" in the URL must be lower case. If the page fails to appear, examine the last line in the IIS server log file in found in SYSTEM32/LogFiles/W3SVC1.

The last line should contain something like: GET "/jakarta/isapi_redirect.dll HTTP1.1", which indicates the ISAPI redirector is recognising that it should handle the request.

You should check the HTTP error code following GET "/...":

  Error 404
  GET "/..." 404
  • Make sure you entered the URL correctly.
  Error 500
  GET "/..." 500
  • Make sure the virtual directory created was called "jakarta".
  • Make sure that the extension_uri setting is correct.
  • Check the workers.properties file and make sure the port setting for worker.ajp13.port is the same as the port specified in the server.xml for the "AJP" connector.
  Error 200 or 403
  GET "/..." 200
  GET "/..." 403
  • Make sure you have checked Execute Access for the jakarta virtual directory in the Advanced Options of the Personal Web Manager.

If the above settings are correct, the index.html page should appear in your browser. You should also be able to click the links to execute some Servlet or JSP examples.


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