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From Vishy Kasar <>
Subject mod_webapp questions..
Date Tue, 01 May 2001 19:41:31 GMT

I have a few questions on connectivity between Apache and TomCat4. I am
a newbie to tomcat, so feel free to brush me aside with pointers to
existing documents or source code.

IMO, The connectivity layer between apache and tomcat has to deal with
the following issues.

1. Protocol:  The protocol used for exchanging messages and the actual
messages themselves. My understanding is WARP is the protocol used by
mod_webapp to connect Apache and TomCat4. WARP is pretty similar to
AJP13 protocol used by mod_jk but more recent and better designed. Is
this understanding correct? Also is the WARP description available
currently under <cvsweb>/connectors/docs/warp.html final?

2. Connection sharing: How are the connections shared between apache and
tomcat4 when using mod_webapp? Some choices are:
    2.1 Connection teared down after each request (simple, stupid and
    2.2 Connection used serially. i.e. Only one message with pending
replies can be active on the connection.
    2.3 Connection multiplexed. i.e. Multiple messages with outstanding
replies can be present.

My understanding is mod_jk employs 2.2 above. What about mod_webapp?

3. Configuration aspects: From reading some archived messages,
I understand that mod_jk is difficult to configure and mod_webapp is
easy. Exactly how it is easy is something I dont understand. With
mod_webapp, does the relevant apache configuration automatically flow to
TomCat4? What about security information? In the WARP protocol messages,
I do not see something to transfer configuration back and forth.

4. Load Balance aspect: If I have one web server with multiple web
containers and want my web server to load balance across multiple
containers (preserving session info), will mod_webapp help me in this
regard? My understanding is mod_jk does through worker list.

On WARP my observation is: We have an industry standard protocol IIOP,
that is pretty solid, solves all the problems encountered here and much
more. Why not use the IIOP (or a subset) to communicate between 'C'
Apache and 'Java' TomCat4?

Here is the summary of question. I appreciate answers or pointers.

- Is WARP a procol pretty similar to AJP13 protocol used by mod_jk but
more recent and better designed?
- Is the WARP description available currently under
<cvsweb>/connectors/docs/warp.html final?
- What is the connection sharing mechanism employed by webapp?
- How does webapp makes life easy in configuration world?
- Does mod_webapp help load balance across multiple web containers?
- Why not use IIOP instead of designing a new wire protocol like WARP?


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