Tags | kubernetes python |
Hard Prerequisites | |
IMPORTANT: Please review these prerequisites, they include important information that will help you with this content. | |
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Soft Prerequisites |
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Let’s setup the Python app on your instance.
First, on the GitHub repository, create a file named app.py
under a folder named python
. This is the app’s source code.
from flask import Flask, jsonify
import psycopg2
app = Flask(__name__)
# Database connection parameters
db_params = {
"dbname": "yourdb",
"user": "youruser",
"password": "yourpassword",
"host": "localhost", # Change this if your database is on a different host
}
# Function to create the "pressed" table
def create_pressed_table():
try:
conn = psycopg2.connect(**db_params)
cur = conn.cursor()
# Check if a row exists in the "pressed" table
cur.execute("CREATE TABLE IF NOT EXISTS pressed (count INTEGER);")
cur.execute("SELECT 1 FROM pressed LIMIT 1;")
if cur.fetchone() is None:
# If no row exists, insert an initial row with count = 1
cur.execute("INSERT INTO pressed (count) VALUES (1);")
else:
# If a row exists, increment the count
cur.execute("UPDATE pressed SET count = count + 1;")
conn.commit()
except Exception as e:
print(str(e))
finally:
if conn:
conn.close()
# Function to get the count from the "pressed" table
def get_pressed_count():
try:
conn = psycopg2.connect(**db_params)
cur = conn.cursor()
# Retrieve the count from the "pressed" table
cur.execute("SELECT count FROM pressed;")
count = cur.fetchone()[0] if cur.rowcount > 0 else 0
return count
except Exception as e:
print(str(e))
return 0
finally:
if conn:
conn.close()
# Define a route to get the status
@app.route('/api/get-status', methods=['GET'])
def get_status():
# Get the count from the "pressed" table
count = get_pressed_count()
return jsonify({'count': count})
# Define a route to increment the "pressed" table
@app.route('/api/pressed', methods=['GET'])
def increment_pressed():
try:
conn = psycopg2.connect(**db_params)
cur = conn.cursor()
# Increment the "pressed" table
cur.execute("UPDATE pressed SET count = count + 1;")
conn.commit()
# Get the updated count
count = get_pressed_count()
return jsonify({'count': count})
except Exception as e:
return jsonify({'error': str(e)})
finally:
if conn:
conn.close()
if __name__ == '__main__':
# Create the "pressed" table if it doesn't exist
create_pressed_table()
app.run(host='0.0.0.0', port=5000) # Replace with your preferred host and port
Next, create a file named myflaskapp.service
under the same folder with the content below. This file will create a service which will ensure our app is running in the backgroud.
[Unit]
Description=My Flask App
After=network.target
[Service]
User=root
WorkingDirectory=/home/ubuntu/umuzi-k8s/python
ExecStart=/home/ubuntu/umuzi-k8s/python/venv/bin/python /home/ubuntu/umuzi-k8s/python/app.py
[Install]
WantedBy=multi-user.target
Save the files, commit and pull the changes from the repository on the EC2 instance.
Now, on the EC2 instance, let’s configure our Python environment.
Create a Python virtual environment to isolate our app dependencies.
# updates the package manager
sudo apt update
# installs Python virtual environment
sudo apt install python3.10-venv
# createa a virtual environment named `vevn`
python3 -m venv /home/ubuntu/umuzi-k8s/python/venv
Now let’s access the virtual environment and install our app’s dependencies.
# activates the virtual environment
source /home/ubuntu/umuzi-k8s/python/venv/bin/activate
# installs the system dependencies for psycopg2
# psycopg2 is used to access the PostgreSQL database from a Python app
sudo apt install build-essential libssl-dev python3-dev libpq-dev -y
# installs the app's dependencies
pip install psycopg2 flask
Setup the Python app’s service.
# copy the service file
sudo cp python/myflaskapp.service /etc/systemd/system/myflaskapp.service
# reload the service daemon
sudo systemctl daemon-reload
# enable and start the Python app
sudo systemctl enable myflaskapp
sudo systemctl start myflaskapp
sudo systemctl status myflaskapp
Run the following command to test if the app is running properly:
# accesses the app's API
# should return {"count":1}
curl http://127.0.0.1:5000/api/get-status