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HAProxy and rsyslog in CentOS 7 with SCL

What is HAProxy?

A quote from the HAProxy's official website:

"HAProxy is a free, very fast and reliable solution offering high availability, load balancing, and proxying for TCP and HTTP-based applications." [1]

Installation in CentOS 7

At the time of writing, the latest available HAProxy version in the default CentOS 7 repository is 1.5. What I want to do here is to use the Software Collections repository to obtain the latest available version instead. Software Collections is a project aimed at providing the possibility to install multiple versions of software. [2]

To enable software collections, install the following package:

# yum install centos-release-scl

Then, to install HAProxy:

# yum install rh-haproxy18

# scl enable rh-haproxy18 bash

# systemctl enable rh-haproxy18-haproxy

# systemctl start rh-haproxy18-haproxy

Let's edit configuration to setup our first app that haproxy will handle for us:

vim /etc/opt/rh/rh-haproxy18/haproxy/haproxy.cfg

This file itself provides lots of useful information on how to configure the proxy. For one, let's change the configuration such that we only redirect all requests from port 5000 to port 80, where we already have an apache application. The first thing to do would be to find frontend main section and change default_backend's value to web. web will be our new backend app that needs to be defined like so:

backend web                                                                       
    server  default 127.0.0.1:80 check

Now, let's configure HAProxy so that it logs all incoming requests. We'd need to start by making rsyslog start listening for incoming connections:

… [3]

Sep 23 21:16:52 localhost.localdomain haproxy[29883]: 109.41.2.109:26831 [23/Sep/2018:21:16:52.573] main web/default 0/0/0/1/1 304 163 - - ---- 2/2/0/0/0 0/0 "GET / HTTP/1.1"

…