flask_consul/main.py

import json
import random
from time import sleep
import uuid
import atexit
import os
import socket, struct
import requests
from flask import Flask
import time
import consul

from logging.config import dictConfig

dictConfig({
    'version': 1,
    'formatters': {'default': {
        'format': '[%(asctime)s] %(levelname)s in %(module)s: %(message)s',
    }},
    'handlers': {'wsgi': {
        'class': 'logging.StreamHandler',
        'stream': 'ext://sys.stdout',
        'formatter': 'default'
    }},
    'root': {
        'level': 'INFO',
        'handlers': ['wsgi']
    }
})

def convert_seconds(seconds):
    if seconds > 0:
    # generated by ChatGPT
        days = seconds // (24 * 60 * 60)
        seconds = seconds % (24 * 60 * 60)
        hours = seconds // (60 * 60)
        seconds = seconds % (60 * 60)
        minutes = seconds // 60
        seconds = seconds % 60
        return (f"{days} days {hours} hours {minutes} minutes {seconds} seconds")
    else:
        return "never"

def get_ip():
    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    s.settimeout(0)
    try:
        # doesn't even have to be reachable
        s.connect(('10.254.254.254', 1))
        IP = s.getsockname()[0]
    except Exception:
        IP = '127.0.0.1'
    finally:
        s.close()
    return IP

def get_default_gateway_linux():
    with open("/proc/net/route") as fh:
        for line in fh:
            fields = line.strip().split()
            if fields[1] != '00000000' or not int(fields[3], 16) & 2:
                continue
            return socket.inet_ntoa(struct.pack("<L", int(fields[2], 16)))


if os.getenv('CONSUL') != None:
    CONSUL = os.getenv('CONSUL')
else: 
    CONSUL=get_default_gateway_linux()

if os.getenv('HOSTNAME') != None:
    HOSTNAME = os.getenv('HOSTNAME')
else: 
    HOSTNAME=get_ip()

BASE_CONSUL_URL = 'http://' +  CONSUL + ':8500'

configuration = {
    'default': {
        'config' : {'default':'config'}
        , 'time' : int(time.time()) 
    }
    , 'consul' :{
        'config' : {}
        , 'time': 0
        , 'state': {
            'status': ''
            , 'time': 0
        }
    }
}

SERVICE_ADDRESS = get_ip()

PORT = 8080 
UUID=str(uuid.uuid5(uuid.NAMESPACE_DNS, f'{SERVICE_ADDRESS}:{PORT}:{HOSTNAME}'))

c = consul.Consul(host=CONSUL)

app = Flask(__name__)

@app.route('/')
def home():
    global configuration
    message = f"Hello World, <br> I`m {HOSTNAME} from {SERVICE_ADDRESS} {PORT} {UUID} <br> my config: {configuration['default']['config']} |"
    if configuration['consul']['config'] != configuration['default']['config']:
        delta_time = convert_seconds(configuration['consul']['time']-configuration['default']['time'])
        message += f"<br>configuration changed {delta_time} ago. new configuration: {configuration['consul']['config']} | default config: {configuration['default']['config']}"
    else:
        message += f'configuration NOT changed'
    message += '<br>'
    message += f"Consul request state: {configuration['consul']['state']['status']} was {convert_seconds(int(time.time()) - configuration['consul']['state']['time'])} ago"
    message += f'<br> <!-- {configuration} -->'
    return message


@app.route('/health')
def hello_world():
    data = {
        'status': 'healthy'
    }
    global configuration
    try:
        _, resp = c.kv.get('PythonApp/config', wait='2s')
        configuration['consul'] = {
            'config' : resp['Value']
            , 'time': int(time.time())
            , 'state': {
                'status': 'OK'
                , 'time': int(time.time())
            }
        }
    except Exception as e:
        configuration['consul']['state'] = {
            'status': 'Failed to fetch'
            , 'time': int(time.time())
        }
        
        # config = {}
        app.logger.debug(f'Get config from consul failed: {e}')
    return json.dumps(data)

@app.route('/register')
def register():
    url = f'{BASE_CONSUL_URL}/v1/agent/service/register'
    data = {
        'Name': 'PythonApp',
        'ID': UUID,
        'Tags': ['flask'],
        'Address': SERVICE_ADDRESS,
        'Port': PORT,
        'Check': {
            'http': f'http://{SERVICE_ADDRESS}:{PORT}/health',
            'interval': '10s'
        }
    }
    res = requests.put(
        url
        , data=json.dumps(data)
        , timeout=15
    )
    return res

def cleanup():
    try:
        sleep(int(random.randrange(1,5)))
        url = f'{BASE_CONSUL_URL}/v1/agent/service/deregister/{UUID}'
        data = {
            'service_id': UUID,
        }

        res = requests.put(
            url,
            data=json.dumps(data)
        )
        app.logger.debug(f'Service registration parameters: {data} | {res.status_code} : {res.text}')
        return f'Response: {res.text} | status_code: {res.status_code}'
    except Exception as e:
        app.logger.debug(f'{e}')
atexit.register(cleanup)

if __name__ == '__main__':
    sleep(1)
    status = ""
    while status != 200:
        try:
            print(f'Registering on consul')
            status = register().status_code
            sleep(int(random.randrange(1,5)))
        except Exception as e:
            print(f'ERROR::::: {e}')
            sleep(int(random.randrange(1,5)))
    app.run(debug=True, host="0.0.0.0", port=PORT)