Configure Apache Load Balancer for High Traffic Website – Outsourced Support | Web Hosting Support

Struggling with a high-traffic website, when there are no performance issues? Then no worries now with Apache load balancer you can manage high-traffic websites hassle-free. (Setup is based on Ubuntu/Debian systems, if you need assistance click here – Get Assistance).

You can follow the below steps to configure the Apache load balancer for
your website to avoid high traffic.

Step 1: Install Apache Modules

To configure the Apache load balancer, we require four Apache modules:

  • mod_proxy: The primary proxy module that redirects traffic and
    enables Apache to serve as a gateway to backend servers.
  • mod_proxy_http: Allows proxying HTTP
    requests
  • mod_proxy_balancer and mod_lbmethod_byrequests: Add a load balancing
    support to the Apache web server.

To install the required Apache modules, open a terminal and run the
following commands.

$ sudo a2enmod proxy
$ sudo a2enmod proxy_http
$ sudo a2enmod proxy_balancer
$ sudo a2enmod lbmethod_byrequests

Step 2: Restart Apache Server

Apply the changes by restarting Apache Server.

$ sudo service apache2 restart

Step 3: Configure backend servers

Installing flask and setting up two servers to run on ports 8080 and 8081
as a backend server will allow us to configure Apache Load Balancer.

$ sudo apt-get update
$ sudo apt-get -y install python3-pip
$ sudo pip3 install flask

The default /backend.py file for Flask returns “Hello World” on
the home page of the request.

from flask import Flask
app = Flask(__name__)
@app.route('/')
def home():
return 'Hello world!'

Let’s duplicate it for our secondary server.

$ sudo cp ~/backend.py ~/backend1.py

In backend1.py, change the “Hello World” message in the last line
to “Hello World 2”.

from flask import Flask
app = Flask(__name__)
@app.route('/')
def home():
return 'Hello world 2!'

Initially, run the First Flask Server

$ FLASK_APP=~/backend.py flask run --port=8080 >/dev/null 2>&1&

and you can run the curl command to test this server.

$ curl http://127.0.0.1:8080/

Output: Hello World!

Now, run the Second Flask Server

$ FLASK_APP=~/backend1.py flask run --port=8081 >/dev/null 2>&1&

and you can run the curl command to test this server.

$ curl http://127.0.0.1:8081/

Output: Hello World 2!

We now have two backend servers that can handle the load. We will divide
the load between these two servers.

Step 4: Setup Apache Load Balancer

To configure the Apache load balancer, we must change the default configuration file. Open the Apache configuration in a text editor.

$ sudo vi /etc/apache2/sites-available/000-default.conf

In the Apache configuration file, add the following lines to the
VirtualHost tag.

<Proxy balancer://mycluster>
BalancerMember http://127.0.0.1:8080
BalancerMember http://127.0.0.1:8081
</Proxy>
ProxyPreserveHost On
ProxyPass / balancer://mycluster/
ProxyPassReverse / balancer://mycluster/

The three directives are:

  • ProxyPreserveHost– It informs Apache to
    retain the original host header and pass it on to back-end servers.
  • ProxyPass – Primary proxy directive.
    This specifies that everything under root (/) should be sent to a server
    back-end cluster of servers. When Apache receives a request for /example, it
    sends it to http://your backend server/example.
  • ProxyPassReverse – informs Apache to change
    the response header in the response received from the back-end server. If the
    back-end server returns a location redirect response, then the client will be
    redirected to the Apache proxy server rather than the back-end server.

Note: The backend server in the Proxy tag is mentioned as balancer://myclustera and inside the Proxy tag each backend server is mentioned as BalancerMember.You can have one or more BalancerMember.

<VirtualHost *:80>
...
<Proxybalancer://mycluster>
BalancerMember http://127.0.0.1:8080
BalancerMember http://127.0.0.1:8081
</Proxy>
ProxyPreserveHost On
ProxyPass / balancer://mycluster/
ProxyPassReverse / balancer://mycluster/
... 
</VirtualHost>

Step 5:Restart Apache
Server

Restart Apache Server
after making the changes.

$ sudo service apache2 restart

Read More: Quick Fix Apache: “module wsgi_module is already loaded, skipping”

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