On 21/08/2012 17:00, Christopher Schultz wrote:
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Miguel,
On 8/21/12 6:25 AM, Miguel González Castaños wrote:
Dear all,
I have a Tomcat web server. From time to time, I need to do some
maintenance and want people not to interact with the Tomcat server
while I'm doing it. The key thing here is that the Tomcat server is
up and running. This is what I want to achieve:
- I want all people to be redirected from 80/443 port at server1 to
a different URL http://server2/maintenance.html except my IP
address (so I can check Tomcat myself).
- If possible, I want this to be transparent to the user, so they
get a http redirect showing the server1 in the client's browser,
not server2 (but this is not that important).
I assume I can use iptables to redirect people to a different web
server, but how can I know that I need to redirect them to the
maintenance.html if that server is serving other web pages too?
I don't know if you want to add this kind of complication to your
environment, but this is pretty much what mod_jk was built for:
distributing requests to one or more back-end Tomcat servers.
With mod_jk's management interface, you can take (load-balanced)
workers out of a pool, upgrade them, then add them back to the pool.
Before you add them back, you can always access them directly if you
have set up an HTTP <Connector> and you can feel free to use any
technique (iptables, bind to 127.0.0.1, etc.) to prevent direct access
to the HTTP port from normal users.
The use of Apache httpd out in front of your app server(s) also means
that you can detect error conditions in the Tomcat instance (like it's
crashed or whatever) and give a semi-nice error message instead of a
connection failure.
This is one of those situations where using Apache httpd out in front
of Tomcat makes some sense: not for performance, but for availability.
See Mladen's article with explains some of the why, what and how of
setting up a mod_jk-based cluster:
http://people.apache.org/~mturk/docs/article/ftwai.html
It makes sense. I will give it a thought. Unfortunately until we migrate
to a bigger server, I'm not sure the overhead of Apache is too much.
Although I know Apache is faster for static content.
Many thanks for your thoughts
Miguel
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