Configuring HAProxy for use with Apache Tomcat

Problem

At $WORK we’ve been evaluating options other than Apache HTTPD as a front-end, loadbalancer, and session manager for Apache Tomcat due to unreasonably high load on the Apache servers, and we came across HAProxy as an option.  Here’s how we ended up configuring HAProxy for Apache Tomcat with sticky sessions!  It seems that few sites were posting exactly how to do this (or maybe I just suck at searching!), so I thought I should.

Installing HAProxy

Luckily, HAProxy is a well-known and mature product and thus should be in your favorite distribution’s package repository.

To install on Debian and derivatives:

apt-get install haproxy

To install on Redhat and derivatives:

yum install haproxy

Configuring HAProxy

For the impatient, here’s a lightly edited version of /etc/haproxy/haproxy.cfg with brief annotations:

# haproxy.cfg
global
    log         127.0.0.1 local2

    chroot      /var/lib/haproxy
    pidfile     /var/run/haproxy.pid
    maxconn     4000
    user        haproxy
    group       haproxy
    daemon

defaults
    mode                    http
    log                     global
    option httplog
    option dontlognull
    option http-server-close
    option forwardfor       except 127.0.0.0/8
    option redispatch
    retries                 3
    timeout http-request    10s
    timeout queue           1m
    timeout connect         10s
    timeout client          1m
    timeout server          1m
    timeout http-keep-alive 10s
    timeout check           10s
    maxconn                 3000

frontend test1
    mode            http
    bind            *:80
    default_backend testback

backend testback
    mode            http
    stats           enable
    stats auth      username:password
    stats uri       /haproxy
    option redispatch
    option forwardfor
    option httpchk  OPTIONS /qds-portal
    balance url_param JSESSIONID check_post
    cookie          JSESSIONID prefix
    server  tc48 host48.example.com:8080 check cookie tomcat48  # tomcat48 = jvmRoute in tomcat/conf/server.xml
    server  tc49 host49.example.com:8080 check cookie tomcat49  # tomcat49 = jvmRoute in tomcat/conf/server.xml