Nginx w/ multiple instances, debug mode

docker-compose.yml

@@ -25,13 +25,25 @@ services:
       timeout: 5s
       retries: 3
 
-  flask:
+  flask_1:
     build: ./flask
-    container_name: flask
+    container_name: flask_1
+    env_file:
+      - .env
+    depends_on:
+      # waiting for the upstream containers to be ready
+      redis:
+        condition: service_healthy
+      db:
+        condition: service_healthy
+    volumes:
+      - ./flask:/app
+
+  flask_2:
+    build: ./flask
+    container_name: flask_2
     env_file:
       - .env
-    ports:
-      - "5000:5000"
     depends_on:
       # waiting for the upstream containers to be ready
       redis:
@@ -52,7 +64,8 @@ services:
       - ./nginx/nginx.conf:/etc/nginx/nginx.conf
       - ./nginx/ssl-certs:/etc/nginx/ssl-certs
     depends_on:
-      - flask
+      - flask_1
+      - flask_2
 
 # to persist container volumes
 volumes:

flask/Dockerfile

@@ -15,10 +15,10 @@ EXPOSE 5000
 RUN adduser --disabled-password --gecos '' flaskuser
 USER flaskuser
 
-# CMD python application.py
+CMD python application.py
 # CMD python application.py run --debug --host 0.0.0.0
 
 # without Flask-SocketIO
 # CMD gunicorn --access-logfile '-' --workers 1 --threads 4 --bind flask:5000 application:application
 # with Flask-SocketIO
-CMD gunicorn --access-logfile '-' --worker-class eventlet --workers 1 --threads 4 --bind flask:5000 application:application
+# CMD gunicorn --access-logfile '-' --worker-class eventlet --workers 1 --threads 4 --bind flask:5000 application:application

flask/application.py

@@ -1,5 +1,5 @@
-from flask import Flask
-from app import create_app, db
+from flask import Flask, jsonify
+from app import create_app, db, socketio
 from flask.cli import FlaskGroup
 
 application = create_app()
@@ -11,5 +11,13 @@ def create_all():
     with application.app_context():
         db.create_all()
 
+import os
+HOSTNAME = os.uname().nodename
+
+@application.route('/hostname')
+def get_hostname():
+    return jsonify({'hostname': HOSTNAME})
+
 if __name__ == "__main__":
-    cli()
+    # cli()
+    socketio.run(application, debug=True, host='0.0.0.0')

nginx/conf.d/server.conf

@@ -6,6 +6,13 @@ server {
     return 301 https://$host$request_uri;
 }
 
+upstream flask_nodes {
+    ip_hash;
+
+    server flask_1:5000;
+    server flask_2:5000;
+}
+
 server {
     listen 443 ssl;
     server_name localhost;
@@ -14,15 +21,15 @@ server {
     ssl_certificate_key /etc/nginx/ssl-certs/localhost.key;
 
     location / {
-        proxy_pass http://flask:5000/;
+        proxy_pass http://flask_nodes/;
         proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
         proxy_set_header X-Forwarded-Proto $scheme;
         proxy_set_header X-Forwarded-Host $host;
         proxy_set_header X-Forwarded-Prefix /;
     }
 
     location /socket.io {
-        proxy_pass http://flask:5000/socket.io;
+        proxy_pass http://flask_nodes/socket.io;
         proxy_http_version 1.1;
         proxy_buffering off;
         proxy_set_header Upgrade $http_upgrade;