How do I use Apache http to proxy to two different tomcat servers?

Question

I have apache httpd that I want to proxy to two different tomcat servers.

I see this: http://tomcat.apache.org/connectors-doc-archive/jk2/proxy.html

But that is only for one tomcat server. What if I had one server running on 8081 in addition to a tomcat running at 8080?

Answer 1

There's an easier way to setup load balancing using mod_proxy_balancer. Simply list the tomcat servers under a balancer list than put that balancer in your ProxyPass:

<Proxy balancer://mycluster>
    BalancerMember http://tomcat1:8080/
    BalancerMember http://tomcat2:8081/
</Proxy>
ProxyPass /test balancer://mycluster 

Answer 2

Apache httpd two out-of-the-box options for proxying to any number of backend Tomcat instances:

1. mod_proxy_http
2. mod_proxy_ajp

They are configured identically to each other, except that the former uses the HTTP protocol for communication and the latter uses the AJP protocol and URLs that start with ajp:// instead of http:// for the backend server. Both can be configured for load-balancing, failover, etc. in the same way. You can proxy to completely separate Tomcat instances (i.e. no load-balancing: just separate backends) by providing separate proxy configuration for separate URL spaces (e.g. /app1 -> Tomcat1 and /app2 -> Tomcat2) or you can configure the two (or more) backend instances for load-balancing, etc.

Specifically, look at the documentation for the following httpd configuration directives:

<Proxy>
BalanceMember
ProxyPass
ProxyPassReverse

You can find documentation for all of these here:

1. http://httpd.apache.org/docs/2.2/mod/mod_proxy.html (General)
2. http://httpd.apache.org/docs/2.2/mod/mod_proxy_http.html (HTTP)
3. http://httpd.apache.org/docs/2.2/mod/mod_proxy_ajp.html (AJP)
4. http://httpd.apache.org/docs/2.2/mod/mod_proxy_balancer.html (load-balancer)

If you want to use the AJP protocol and you have more complex configuration needs, you can also use mod_jk (not mod_jk2, which is an old, dead, abandoned, completely irrelevant project, now). You can find out more about mod_jk on the Tomcat site here: http://tomcat.apache.org/connectors-doc/

mod_jk has a radically different configuration procedure and a lot more AJP-specific options than mod_proxy_ajp.

The (short) documentation you mentioned in your original post (from the old mod_jk2 docs) points to Apache httpd's mod_proxy_ajp and mod_proxy_balancer modules (though it points to the unstable httpd 2.1, which was the bleeding-edge at the time that documentation was written). You were on the right track: you just needed to keep reading. You can definitely proxy to as many backend instances of Tomcat as you want with any of the modules described here.

Answer 3

You can install HAProxy on either 3rd server which will work as LB to both of them or you can install HAProxy on any one of them and then do following configuration.

To install HAProxy (if you're running Ubuntu/Debain distro)

  $ sudo apt-get install haproxy
  # Setup config file in /etc/haproxy/haproxy.cnf per requirement
  # change /etc/default/ to Enabled = 1 and restart haproxy service

after setup do following mods in config:

$ sudo vim /etc/haproxy/haproxy.cfg

global
        maxconn 4096
        user haproxy
        group haproxy
        daemon

defaults
        log     global
        mode    http
        option  httplog
        option  dontlognull
        retries 3
        option  redispatch
        maxconn 2000
        contimeout      5000
        clitimeout      50000
        srvtimeout      50000

listen webcluster *:80
        mode    http
        stats   enable
        stats   auth us3r:passw0rd
        balance roundrobin
        option httpchk HEAD / HTTP/1.0
        option forwardfor
        cookie LSW_WEB insert
        option httpclose
        server web01 192.168.0.1:8080 cookie LSW_WEB01 check
        server web02 192.168.0.2:8081 cookie LSW_WEB02 check

Once done, restart HAProxy service by:

$ sudo service haproxy restart

Here 192.168.0.1 and 192.168.0.2 can be your two servers one can be running on port 8080 and another can be on 8081.

Ref. Post: http://www.leaseweblabs.com/2011/07/high-availability-load-balancing-using-haproxy-on-ubuntu-part-1/ You will also find online help if you will google about how to setup haproxy on your linux distribution if you're not using Ubuntu/Debain. But yes you can bet on it as it's proven tool for the job.