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 steps below 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”
Health Checks for Load Balancing
How to setup SSL for Elastic Load Balancer in AWS
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