Simple Comment Web Server

This is a simple web server that allows users to post comments. It is written in Python and uses the Flask framework. The server stores the comments in a SQLite database. The database file is comments.db. It is located in the data folder.

Before you start

You will need to install the following:

sudo apt-get install libsqlite3-dev

pip3 install -r requirements.txt

Test the server

• Start the server

  • To start the server, run the following command:

    ./start-app.sh

  • In start-app.sh, you can change the port number and the host name. The default port number is 5000 and the default host name is 127.0.0.1.
  • -w parameter is used to specify the number of workers. The default number of workers is 4.

• Stop the server

  • Press Ctrl+C to stop the server.

Deploy the server

To use the system service manager (such as systemd) to manage a Gunicorn process and ensure it runs continuously on your server, you can follow these steps:

• Edit the content of comment-webserver.service
  • Description: A description of the service.
  • User and Group: The user and group under which the service should run.
  • WorkingDirectory: The root directory of your Comment Web Server.
  • ExecStart: The command to start the Gunicorn process.
  • Restart: Specifies when the service should be restarted. "always" means it will automatically restart whenever it exits.
• Copy comment-webserver.service to /etc/systemd/system

sudo cp comment-webserver.service /etc/systemd/system

• Enable and start the service

sudo systemctl enable comment-webserver.service
sudo systemctl start comment-webserver.service

Or reload the service if you have made any changes to the service file

sudo systemctl daemon-reload

• Manage the service
  • Check the status of the service

  sudo systemctl status comment-webserver.service

  • Stop the service

  sudo systemctl stop comment-webserver.service

  • Restart the service

  sudo systemctl restart comment-webserver.service

  • Disable the service

  sudo systemctl disable comment-webserver.service

Example

index.html is a simple web page that allows users to test the server. It is located in the templates folder.

In the web page, users can enter their name and a comment. When they click the Submit button, the comment will be posted to the server.

Tools

In the tools folder, there are serveral Python scripts:

• delete.py: delete one comment from the database by id
• select-1.py: select one comment from the database by id
• select-all.py: select all comments from the database

Appendix

Configuring Apache2 as a Reverse Proxy

• Add ProxyPass and ProxyPassReverse to the VirtualHost configuration file (/etc/apache2/sites-available/default-ssl.conf)

        <VirtualHost 172.31.19.160:443>
                ServerName www.example.com
                ServerAlias example.com
                ServerAdmin webmaster@localhost
                DocumentRoot /var/www/html

                ErrorLog ${APACHE_LOG_DIR}/error.log
                CustomLog ${APACHE_LOG_DIR}/access.log combined

                SSLEngine on
                SSLCertificateFile /etc/letsencrypt/live/example.com/fullchain.pem
                SSLCertificateKeyFile /etc/letsencrypt/live/example.com/privkey.pem

                SSLProxyEngine on
                SSLProxyVerify none
                SSLProxyCheckPeerCN off
                SSLProxyCheckPeerName off

                <Location /comment>
                        ProxyPass https://localhost:5000/
                        ProxyPassReverse https://localhost:5000/
                </Location>
        </VirtualHost>

• Enable the proxy modules

sudo a2enmod proxy
sudo a2enmod proxy_http

• Restart Apache2

sudo systemctl restart apache2

Some Bugs

These bugs are found in /var/log/apache2/error.log during the test of the server.

• SSL Proxy requested for yourweb.com:443 but not enabled [Hint: SSLProxyEngine]

  • Solution: add SSLProxyEngine on to the VirtualHost configuration file

• Error during SSL Handshake with remote server returned by /comment/query-comments

  • Solution: add SSLProxyVerify none (SSLProxyCheckPeerCN off and SSLProxyCheckPeerName off) to the VirtualHost configuration file