Configure a Back End for a Web Application

In this lab, we set up a back end for the existing front end of a web application. We do this by creating a proper folder that will hold the code of our back end. Then we proceed to create a systemd file which will be used to start, stop, and get the status of this process at any given time. In addition to this, we will daemonize the process in this manner.

In general, we might ask ourselves what does this have to do with Apache web server? If we have a front-end web application served to us via the Apache web server, there likely exists a back end that will fetch the content to be presented by the front end. In addition to this, Apache web server doesn’t necessarily need to be configured to serve websites. It can also serve as a reverse proxy for various API’s and serve pretty much any content imaginable. Therefore, it stands to reason we should know how to configure Apache web server to interact not only with the user, website, or front end, but the back end as well.

Learning Objectives

Successfully complete this lab by achieving the following learning objectives:

Create a New Directory for the Back End and Move `app.py` to the Newly-Created Directory

mkdir /home/cloud_user/Backend

sudo mv /home/cloud_user/HardeningApache-master/app.py /home/cloud_user/Backend/

sudo chown cloud_user:cloud_user /home/cloud_user/Backend/app.py

Install Dependencies: python36.x86_64, python36-devel.x86_64, “Development Tools”, python36-pip, Flask, flask-cors, psutil, and tcpdump, then Open Port 65535 with `firewalld`

sudo yum install epel-release

sudo yum update

sudo yum install python36

sudo yum install python36-devel

sudo yum groupinstall "Development Tools"

sudo yum install python36-pip

ln -s /usr/local/bin/pip3 /usr/bin/pip3

sudo pip3 install Flask

sudo pip3 install flask-cors

sudo pip3 install psutil

sudo yum install tcpdump

sudo firewall-cmd --permanent --add-port=65535/tcp

sudo firewall-cmd --reload

Create a systemd File for Our Back End Called “flaskapp.service” in `/etc/systemd/system/`

sudo vim /etc/systemd/system/flaskapp.service

[Unit]
Description=API_Backend
After=network.target

[Service]
User=root
Group=root
WorkingDirectory=/home/cloud_user/Backend
Environment=FLASK_ENV=development
Environment=FLASK_APP=/home/cloud_user/Backend/app.py
ExecStart=/usr/local/bin/flask run -h 0.0.0.0 -p 65535
Restart=always

[Install]
WantedBy=multi-user.target

Save and Close

sudo systemctl daemon-reload

sudo systemctl start flaskapp

sudo systemctl enable flaskapp

Configure the Front End to Be Able to Access the Back End and Test If the Back End Works

vim /var/www/html/index.html

Insert the Server Public IP address here

var base_url = 'http://<Server_Public_IP>:65535';

Save and close

ESC
:wq
ENTER

Test if it works

curl http://<Server_Public_IP>:65535/log_messages

What are Hands-on Labs

Hands-on Labs are real environments created by industry experts to help you learn. These environments help you gain knowledge and experience, practice without compromising your system, test without risk, destroy without fear, and let you learn from your mistakes. Hands-on Labs: practice your skills before delivering in the real world.