Answers:
这些模块的优缺点比较存在 http://blog.jboss.org/
mod_proxy
* Pros:
o No need for a separate module compilation and maintenance. mod_proxy,
mod_proxy_http, mod_proxy_ajp and mod_proxy_balancer comes as part of
standard Apache 2.2+ distribution
o Ability to use http https or AJP protocols, even within the same
balancer.
* Cons:
o mod_proxy_ajp does not support large 8K+ packet sizes.
o Basic load balancer
o Does not support Domain model clustering
mod_jk
* Pros:
o Advanced load balancer
o Advanced node failure detection
o Support for large AJP packet sizes
* Cons:
o Need to build and maintain a separate module
如果您希望留在Apache的土地上，还可以尝试使用较新的mod_proxy_ajp，它使用AJP协议与Tomcat进行通信，而不是普通的旧HTTP，但可以利用mod_proxy来完成工作。
mod_proxy_*变体上都遇到了更多麻烦，并且已mod_jk成功用于生产中。