We plan to setup a 3 Servers for A Java Web Application.  These 3
servers are going to be Web Servers, we have seprate load balanced
MySQL servers.

We plan to implement this way:

1. 3 Servers would have 2 Tomcat instances running on different ports.
2. These two Tomcat instances are load balanced using Mod_JK. So there
is no down time on Deployments
3.  All these 3 Servers  are LoadBalanced using Mod_JK

Can you please share your suggestions on setting up a HA with Tomcat
5.5

Thanks

If this is a business project, it sounds like speaking with an experienced
technical person could save a great deal of pain.

Here's some examples:

1) Reverse proxy grab bag:

   - Remove dead backends automatically.  Duh.
   - Never show internal error pages publicly, show entertaining pages
   instead that mean different things internally.  Graceful degradation/feature
   darkmode for +2 overcapacity awesome.
   - Sanitized *X-Backend-Server* host header is often useful.
   - Use a combination of haproxy, nginx, varnish and/or ipvs
   (ldirectord/keepalived) up front.  If resources are plentiful, opt for fancy
   stuff netscaler or f5.  I like HA pfsense for cost-containment.  Also, I
   can't say enough good things about varnish for awesomeness.

2) For anything substantial, consider a J2EE container that supports
jopr/jon or similar monitoring tool that does J2EE well.

3) Hosted HA MySQL can have latency issues and should be stress tested.

Non-technical:

0) The number of servers doesn't matter as long as the number is always
greater than 1 and no resource is completely saturated.  Scale with a
capacity load-predicting cloud controller automatically.

1) Architecture should be allowed to evolve and respond to pain-points
rather than being planned and optimized too soon (except when it comes to
security and disaster recovery).  Idle servers are wasted money by
definition.

2) Start small.  Don't go for big solutions right away unless your team
works with it on a daily basis.  Complicated breaks and is insane to
diagnose.  (Any guess why I know this?)

3) Don't promote boxes from dev to qa to prod.  Promote build artifacts and
configuration management scripts that are the same (except passwords, ip,
lun wwn, etc.) across all environments.  Deploy fresh everything every time.
 (Many reasons for this.)

4) Run nonfunctional tests on infrastructure, including performance,
automatically.  Fail the build if below thresholds.  Must mention versioning
code and system infrastructure for this to work effectively.

Barry