app.py

import sqlite3

from flask import Flask, jsonify, json, render_template, request, url_for, redirect, flash
from werkzeug.exceptions import abort
from datetime import datetime
import logging
import sys


# Count all database connections
db_connection_count = 0

# Function to get a database connection.
# This function connects to database with the name `database.db`
def get_db_connection():
    connection = sqlite3.connect('database.db')
    connection.row_factory = sqlite3.Row
    return connection

# Function to get a post using its ID
def get_post(post_id):
    connection = get_db_connection()
    post = connection.execute('SELECT * FROM posts WHERE id = ?',
                        (post_id,)).fetchone()
    connection.close()
    return post

#Function that logs messages
def log_message(message, code = 0):
    '''
    logs the logging messages.
    message: logging message
    code: detects normal log or error. default is 0, if not provided
     if 0: normal log
        1: error log  
    '''
    time = datetime.now().strftime("%m/%d/%Y, %H:%M:%S")
    if code == 0:
        app.logger.info('{time} | {message}'.format(time=time, message=message))
    else:
        app.logger.error('{time} | {message}'.format(time=time, message=message))

# Define the Flask application
app = Flask(__name__)
app.config['SECRET_KEY'] = 'your secret key'

# Define the main route of the web application 
@app.route('/')
def index():
    connection = get_db_connection()
    posts = connection.execute('SELECT * FROM posts').fetchall()
    connection.close()
    return render_template('index.html', posts=posts)

# Define how each individual article is rendered 
# If the post ID is not found a 404 page is shown
@app.route('/<int:post_id>')
def post(post_id):
    post = get_post(post_id)
    if post is None:
      log_message('Article id no. "{id}" doesn\'t exist!'.format(id = post_id), 1)
      return render_template('404.html'), 404
    else:
      title = post['title']
      log_message('Article "{title}" retrieved!'.format(title = title))
      return render_template('post.html', post=post)

# Define the About Us page
@app.route('/about')
def about():
    log_message('About US page retrived')
    return render_template('about.html')

# Define the post creation functionality 
@app.route('/create', methods=('GET', 'POST'))
def create():
    if request.method == 'POST':
        title = request.form['title']
        content = request.form['content']

        if not title:
            flash('Title is required!')
        else:
            connection = get_db_connection()
            connection.execute('INSERT INTO posts (title, content) VALUES (?, ?)',
                         (title, content))
            connection.commit()
            connection.close()
            log_message('A new article, with title: "{title}" created!'.format(title = title))

            return redirect(url_for('index'))

    return render_template('create.html')

# Define healthz endpoint
@app.route('/healthz')
def healthz():
    response = app.response_class(
        response = json.dumps(
            {"result":"OK - healthy"}),
            status = 200,
            mimetype = 'application/json'
    )

    return response

# Define metrics endpoint
@app.route('/metrics')
def metrics():
    connection = get_db_connection()
    posts = connection.execute('SELECT * FROM posts').fetchall()
    connection.close()
    post_count = len(posts)
    response = app.response_class(
        response = json.dumps(
            {"db_connection_count": db_connection_count, "post_count": post_count}),
            status = 200,
            mimetype = 'application/json'
    )

    return response

# start the application on port 3111
if __name__ == "__main__":
   fh = logging.FileHandler('app.log')
   soh = logging.StreamHandler(sys.stdout)
   seh = logging.StreamHandler(sys.stderr)
   handlers = [seh, soh, fh]
   logging.basicConfig(handlers=handlers, level=logging.DEBUG)
   app.run(host='0.0.0.0', port='3111')