API Server Set up Documentation - Python Flask

Reference online resource

• Ubuntu 18.04
• Ubuntu 16.04

Prerequisites

• Ubuntu Server 18.04/16.04
• DNS

Server Initial Set up

Install primary python packages and nginx

Run commands

• sudo apt-get update
• sudo apt-get install python3-pip python3-dev nginx
• sudo apt-get install libpq-dev
• sudo apt-get install libssl-dev

Postgres Database set Up

Install Postgress SQL:

• Run Command sudo apt-get install postgresql

Create Postgres user and password:

• Run command sudo su postgres. Switches to postgres user
• Run command psql in postgres user shell
• Run command CREATE USER <username> WITH SUPERUSER PASSWORD '<password>'. Enter user username and password fot the DB. For ex: CREATE USER agmt WITH SUPERUSER PASSWORD 'pass&14'

Create Database:

• Open New Terminal and run command createdb <db_name>

Set Environment variables: (Command -> gedit .bashrc from home directory)

• Paste follwing with the credentials to the bashrc file.

  export AGMT_SENDINBLUE_KEY="<send_in_blue_key>"
  export AGMT_HS256_SECRET="<jwt_token_key>"
  export AGMT_POSTGRES_HOST="localhost"
  export AGMT_POSTGRES_PORT="5432"
  export AGMT_POSTGRES_USER="<db_user>"
  export AGMT_POSTGRES_PASSWORD="<db_password>"
  export AGMT_POSTGRES_DATABASE="<db_name>"
  

Python Virtual Environment

Install Virtual Environment

• Run command sudo pip3 install virtualenv

Create Virtual Environment

• Run Command virtualenv myprojectenv. You can enter your custom name instead of myprojectenv.

Activate Virtual Environment

• Run Command source myprojectenv/bin/activate. Activate the virtual environment before installing dependencies.

Set Up your Flask Application

Clone Project and Install dependencies

• Clone project repo to server
• Navigate to project directory containing the requirements.txt file.
• Install Python dependencies by running command pip3 install -r requirements.txt

Create Initial DB tables

• Navigate to project directory containing the db.sql file. (Inside agmt folder)
• Run Command psql -d <db_name> -f ./db.sql

Test Flask App

• Run Command gunicorn main:app inside the project folder containing the main.py file.
• If the gunicorn server has started successfully, close and set up Nginx and Gunicorn WSGI.

Set up and enable the configuration files for Flask API server

• Assuming the Server user Name is amt, python virtual environment name is venv3, the project folder name is vachan-api and the main.py file is in vachan-api/agmt/ folder then the config files will be like:
• Save config files in project directory named vachanconfig

Set up Gunicorn

Gunicorn config file

• Copy and edit the files according to the project credentials and directories and save file as gunicorn.service. You could use your custom name for the file.

  [Unit]
  Description=gunicorn daemon
  After=network.target
  
  [Service]
  User=amt
  Group=amt
  WorkingDirectory=/home/amt/vachan-api/agmt
  Environment="AGMT_SENDINBLUE_KEY=<send_in_blue_key>"
  Environment="AGMT_HS256_SECRET=<jwt_algorithm_key>"
  Environment="AGMT_POSTGRES_USER=<db_user_name>"
  Environment="AGMT_POSTGRES_PASSWORD=<db_password>"
  Environment="AGMT_POSTGRES_DATABASE=<db_name>"
  Environment="AGMT_HOST_API_URL=<api_url>"
  Environment="AGMT_HOST_UI_URL=<UI_url>"
  ExecStart=/home/amt/venv3/bin/gunicorn --workers 3 --bind unix:/home/amt/vachan-api/agmt/agmt.sock   main:app --timeout=18000
  
  [Install]
  WantedBy=multi-user.target
  

Link files in systemd folder

• Run Command to create sym link of the gunicorn.service file in systemd folder
  • sudo ln -s /home/amt/vachan-api/vachnaconfig/gunicorn.service /etc/systemd/system/

Start Gunicorn service

• Run the commands
  • sudo systemctl start gunicorn.service
  • sudo systemctl enable gunicorn.service

Set up Nginx config file

Nginx file

• Copy and edit the files according to the project credentials and directories and save file as nginx.conf. You could use your custom name for the file.

• For enabling ssl refer online documentation.

  server {
      listen 80;
      server_name <server_domain_name>;
  
     location / {
          include proxy_params;
          proxy_pass http://unix:/home/amt/vachan-api/agmt/agmt.sock;
          proxy_read_timeout 18000;
          proxy_connect_timeout 18000;
          proxy_send_timeout 18000;
          send_timeout 18000;
      }
  
  }
  

Link files to sites-enabled

• nginx.conf file has to be linked first to sites-available and from sites-available to sites-enabled.
• Run the commands
  • sudo ln -s /home/amt/vachan-api/vachnaconfig/nginx.conf /etc/nginx/sites-available/
  • sudo ln -s /etc/nginx/sites-available/nginx.conf /etc/nginx/sites-enabled
• Run command sudo nginx -t to check for syntax errors in the nginx.conf file.

Start Nginx process with our latest config

• Run Command sudo systemctl restart nginx