Links Contents | | 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.
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| 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 talk to Tomcat. Historically,
Apache has always been much faster than Tomcat at serving static content.
The idea is to let Apache serve the static content when possible, then
proxy the request back to Tomcat for Tomcat related content.
Which connector: mod_jserv, JK, JK2, mod_webapp or mod_proxy?
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Stay away from mod_webapp, aka warp. It is deprecated and unsupported
due to lack of developer interest and there are better options such
as jk and jk2. It WILL NOT run on windows.
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mod_jserv at this point is unsupported and will not be supported
in Tomcat 5. mod_jserv was the original connector which supported
the ajp protocol.
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mod_jk is great and should be used for production. It is getting
fixes as needed (which is now rare).
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jk2 is a refactoring of mod_jk and uses the Apache Portable
Runtime (apr). If you are using Apache 2.0,
you'll might want to use jk2. But this may not be production
worthy for everyone. (YMMV) jk2 has quirks which may not be acceptable
to all.
- mod_proxy. A cheap way to proxy without the hassles of configuring JK.
This solution lacks sticky session load balancing. If you don't
need some of the features of jk, jk2 - this is a very simple
alternative.
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 upcoming performance of Tomcat 5, performance reasons
become harder to justify. So here are the issues to discuss in
integrating vs not.
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Clustering. By using Apache as a front end you can let Apache act as a
front door to your content to multiple Tomcat instances. If one of your
Tomcats fails, Apache
ignores it and your Sysadmin can sleep through the night. This point
could be ignored if you use a hardware loadbalancer and Tomcat's
clustering capabilities.
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Clustering/Security. You can also use Apache as a front door to different
Tomcats for
different URL namespaces (/app1/, /app2/, /app3/, or virtual hosts).
The Tomcats can then be each in a protected area
and from a security point of view, you only need to worry about the
Apache server. Essentially, Apache becomes a smart proxy server.
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Security. This topic can sway one either way. Java has the security
manager while Apache has a larger mindshare and more tricks with
respect to security. I won't go into this
in more detail, but let Google be your friend. Depending on your scenario,
one might be better than the other. But also keep in mind, if you run
Apache with
Tomcat - you have two systems to defend, not one.
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Add-ons. Adding on CGI, perl, PHP is very natural to Apache. Its
slower and more
of a kludge for Tomcat. Apache also has hundreds of modules that can
be plugged in
at will. Tomcat can have this ability, but the code hasn't been
written yet.
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Decorators! With Apache in front of Tomcat, you can perform any number
of decorators that
Tomcat doesn't support or doesn't have the immediate code support.
For example,
mod_headers, mod_rewrite, and mod_alias could be written for Tomcat,
but why reinvent the wheel when Apache has done it so well?
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Speed. Apache is faster at serving static content than Tomcat. But unless
you have a high traffic site, this point is useless. But in some scenarios,
tomcat can be faster than apache. So benchmark YOUR site.
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Socket handling/system stability. Apache has better socket handling
with respect
to error conditions than Tomcat. The main reason is Tomcat must perform
all its socket handling via the JVM which needs to be cross platform.
The problem
is socket optimization is a platform specific ordeal. Most of the
time the java
code is fine, but when you are also bombarded with dropped connections,
invalid
packets, invalid requests from invalid IP's, Apache does a better job
at dropping these error conditions than JVM based program. (YMMV)
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Here
is a great response from Craig R. McClanahan. If you have free time,
read emails by him in any of the list archives. You'll learn a lot.
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.
JK2 doesn't seem to be using my settings in my
workers2.properties file
such as creating the shm file or mapping the URIs listed to Tomcat,
what's wrong?
JK2 is not finding your workers2.properties file.
Specify it's location in your httpd.conf file by adding:
JkSet config.file /full/system/path/to/workers2.properties
Thread which spawned this question.
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?
Where can I download a binary distribution of my connector?
You can't: 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
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