Preface

Please see the Other Resources Link for other pages describing how they were able to link Tomcat with a connector. With luck, someone documented their experience in an environment which is similar to yours.

Here is a link to the JK Connectors. It contains more configuration and installation information.

Please note, jk2 is no longer supported. Please use mod_jk instead.

Questions

  1. What is JK (or AJP)?

  2. Which connector: mod_jk or mod_proxy?

  3. What about mod_jserv, mod_jk2, mod_webapp (aka warp)?

  4. Why should I integrate Apache with Tomcat? (or not)

  5. At boot, is order of start up (Apache vs Tomcat) important?

  6. Is there any way to control the content of automatically generated mod_jk.conf-auto?

  7. How do I bind to a specific ip address?

  8. Where can I download a binary distribution of my connector?

  9. I'm having strange UTF-8 issues with my request parameters.

  10. How do I configure apache tomcat connectors for a heavy load site?

Answers

What is JK (or AJP)?

AJP is a wire protocol. It an optimized version of the HTTP protocol to allow a standalone web server such as Apache to talk to Tomcat. Historically, Apache has been much faster than Tomcat at serving static content. The idea is to let Apache serve the static content when possible, but proxy the request to Tomcat for Tomcat related content.


Which connector: mod_jk or mod_proxy?

Here are some anecdotal comments from members of the Tomcat community:

I have been using mod_jk for a very long time and I saw (at the time) only one reason to make the switch to mod_proxy_ajp: it is bundled with Apache and so you (likely) don't have to build the module yourself.

That said, simple configurations are *way* more simple in mod_proxy_ajp than with mod_jk, although the (somewhat) recent addition of JkWorkerProperty and JkMount "extensions" do help quite a bit.

mod_proxy_ajp can also be trivially swapped-out with mod_proxy_http just by changing the URLs in your ProxyPass and ProxyPassReverse directives to say http:// (or https://) instead of ajp://. This might help you if you need to switch protocols for debugging purposes or if you suddenly need switch to HTTPS to secure the traffic without any external configuration (e.g. stunnel or VPN).

mod_proxy also supports ProxyPassMatch which lets you use regular expressions in your URL mappings, which mod_jk's JkMount does not (though you *can* use <LocationMatch> along with SetHandler in order to achieve the same result, it's a cleaner configuration with mod_proxy).

That said, I have found that mod_jk supports more complicated configurations where I have struggled to get mod_proxy_ajp to do the same. Specifically, overlapping URL spaces that must be mapped to separate workers. Technically speaking, I suppose you could use lots of ProxyPassMatch directives and/or have a complex regular expression to direct the various URLs, but again you end up with a rather messy configuration that way. Messy configurations are a maintenance risk as well as at risk of becoming "arcane knowledge" that nobody actually understands and so they are afraid to modify it for any reason.

Generally, mod_jk will get fixed faster than mod_proxy_ajp due to its independent release cycle: the httpd folks might have a fix for a problem but it doesn't get released for a while due to testing of other components, etc. At this point, mod_proxy_ajp has (IMHO) reached a point of stability that this is less of an issue than it used to be.

At this stage, there is no reason for me to move any of my projects from mod_jk to mod_proxy_ajp but if I were starting from scratch, I might choose mod_proxy_ajp solely due to its binary availability and simple configuration. If the configuration became complicated to the extent that switching to mod_jk were a good option, then I'd move.

As for performance, I have no data on that one way or another. I would suspect that mod_jk has a slight performance advantage because it has been especially designed for the purpose rather than mod_proxy_ajp which must support the mod_proxy API and might have a bit more plumbing code to accomplish that. I would be surprised if you could detect any performance difference between the two if you were to test them both faithfully and with compatible configurations. If anyone has relative performance data between mod_jk and mod_proxy_ajp, I'd be happy to read it. (http://markmail.org/message/u5v4aiejluzy7tde)

What about mod_jserv, mod_jk2, mod_webapp (aka warp)?

All of these connectors have been abandoned long ago. Do not use any of them.

mod_jk2 sounds like it could be an updated version of mod_jk, it is not: it was an abortive effort whose features have been re-incorporated into mod_jk.

For historical purposes, and emphasis:


Why should I integrate Apache with Tomcat? (or not)

There are many reasons to integrate Tomcat with Apache. And there are reasons why it should not be done too. Needless to say, everyone will disagree with the opinions here. With the performance of Tomcat 5 and 6, performance reasons become harder to justify. So here are the issues to discuss in integrating vs not.


At boot, is order of start up (Apache vs Tomcat) important?

No. This way - either apache or tomcat can be restarted at any time independent of one another.


Is there any way to control the content of automatically generated mod_jk.conf-auto? I need my own specific commands added to it.

There really is no need to. Just copy the automatically generated mod_jk.conf-auto and edit it manually to your preference. None of production tomcat installations really use mod_jk.conf-auto as it is.


How do I bind to a specific ip address?

Each Connector element allows an address property. See the HTTP Connector docs or the AJP Connector docs.


Where can I download a binary distribution of my connector?

You cannot: you need to download the source and compile it for your platform. The source distributions are available from the standard location. Note that JPackage.org has RPM distributions for the connectors as well as tomcat itself: JPackage.org


I'm having strange UTF-8 issues with my request parameters.

See Character Encoding


How do I configure apache tomcat connectors for a heavy load site?

See Performance and Monitoring


CategoryFAQ

FAQ/Connectors (last edited 2013-01-30 00:30:32 by KonstantinKolinko)