init

Dockerfile

@@ -0,0 +1,19 @@
+# start by pulling the python image
+FROM python:3.8-alpine
+
+# copy the requirements file into the image
+COPY ./requirements.txt /app/requirements.txt
+
+# switch working directory
+WORKDIR /app
+
+# install the dependencies and packages in the requirements file
+RUN pip install -r requirements.txt
+
+# copy every content from the local file to the image
+COPY . /app
+
+# configure the container to run in an executed manner
+ENTRYPOINT [ "python" ]
+
+CMD ["main.py" ]

main.py

@@ -0,0 +1,156 @@
+import json
+import random
+from time import sleep
+import uuid
+import atexit
+import os
+import socket, struct
+import requests
+from flask import Flask
+
+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 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()
+
+BASE_CONSUL_URL = 'http://' +  CONSUL + ':8500'
+HOSTNAME = os.getenv('HOSTNAME')
+
+config = {'default':'config'}
+prev_config = {'default':'config'}
+changed = 0
+SERVICE_ADDRESS = get_ip()
+
+PORT = 8080 
+UUID=str(uuid.uuid5(uuid.NAMESPACE_DNS, str(SERVICE_ADDRESS) + ":" + str(PORT) + ":" + HOSTNAME))
+
+c = consul.Consul(host=CONSUL)
+
+app = Flask(__name__)
+
+@app.route('/')
+def home():
+    global config
+    global prev_config
+    global changed
+    if changed == 1:
+        ad = f'<br>configuration changed. new configuration: {config} | prev config: {prev_config}'
+        if config != {}:
+            prev_config = config
+        changed = 0
+    else:
+        ad = f'configuration NOT changed: {config}'
+    return f"Hello World, <br> I`m {HOSTNAME} from {SERVICE_ADDRESS} {PORT} {UUID} <br> my config: {config} | {ad}"
+
+
+@app.route('/health')
+def hello_world():
+    data = {
+        'status': 'healthy'
+    }
+    global config
+    global prev_config
+    global changed
+    try:
+        _, resp = c.kv.get('PythonApp/config', wait='2s')
+        resp_config = resp['Value']
+        if resp_config != prev_config:
+            changed = 1
+            config = resp_config
+    except Exception as e:
+        # config = {}
+        app.logger.debug(f'Get config from consul failed: {e}')
+    return json.dumps(data)
+
+@app.route('/register')
+def register():
+    url = BASE_CONSUL_URL + '/v1/agent/service/register'
+    data = {
+        'Name': 'PythonApp',
+        'ID': UUID,
+        'Tags': ['flask'],
+        'Address': SERVICE_ADDRESS,
+        'Port': PORT,
+        'Check': {
+            'http': 'http://{address}:{port}/health'.format(address=SERVICE_ADDRESS, port=PORT),
+            'interval': '10s'
+        }
+    }
+    res = requests.put(
+        url,
+        data=json.dumps(data)
+    )
+    return res
+
+def cleanup():
+    try:
+        sleep(int(random.randrange(1,5)))
+        url = 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:
+            app.logger.debug(f'Registering on consul')
+            status = register().status_code
+            sleep(int(random.randrange(1,5)))
+        except Exception as e:
+            app.logger.debug(f'ERROR::::: {e}')
+    app.run(debug=True, host="0.0.0.0", port=PORT)

requirements.txt

@@ -0,0 +1,3 @@
+flask
+python-consul
+requests