Use docker discover host instead of using a environment variable way

nginx-wsgi-flask/README.md

@@ -11,12 +11,10 @@ Project structure:
 │   ├── app.py
 │   ├── Dockerfile
 │   ├── requirements.txt
-│   └── wsgi.py
 └── nginx
     ├── default.conf
     ├── Dockerfile
     ├── nginx.conf
-    └── start.sh
 ```
 
 [_compose.yaml_](compose.yaml)
@@ -56,15 +54,15 @@ Listing containers must show two containers running and the port mapping as belo
 
 ```bash
 $ docker ps
-CONTAINER ID   IMAGE            COMMAND                  CREATED              STATUS                        PORTS                              NAMES
-bde3f29cf571   ...nginx-proxy   "/docker-entrypoint.…"   About a minute ago   Up About a minute (healthy)   0.0.0.0:80->80/tcp                 ...nginx-proxy_1
-86c44470b547   ...flask-app     "gunicorn -w 3 -t 60…"   About a minute ago   Up About a minute (healthy)   5000/tcp, 0.0.0.0:8000->8000/tcp   ...flask-app_1
+CONTAINER ID   IMAGE            COMMAND                  CREATED              STATUS                          PORTS                   NAMES
+bde3f29cf571   ...nginx-proxy   "/docker-entrypoint.…"   About a minute ago   Up 4 seconds (health: starting) 0.0.0.0:80->80/tcp      ...nginx-proxy_1
+86c44470b547   ...flask-app     "gunicorn -w 3 -t 60…"   About a minute ago   Up 5 seconds (health: starting) 0.0.0.0:53323->8000/tcp ...flask-app_1
 ```
 
-After the application starts, navigate to `http://localhost:80` in your web browser or run:
+After the application starts, run the command in a terminal:
 
 ```bash
-$ curl localhost:80
+$ curl localhost
 Hello World!
 ```
 
@@ -79,6 +77,35 @@ Removing nginx-wsgi-flask_flask-app_1   ... done
 Removing network nginx-wsgi-flask_default
 ```
 
+Deploy and scale the application. Create three different instances.
+
+```bash
+$ docker compose up -d --scale flask-app=3
+✔ Network nginx-wsgi-flask_default          Created 0.0s
+✔ Container nginx-wsgi-flask-flask-app-1    Started 0.4s
+✔ Container nginx-wsgi-flask-flask-app-3    Started 0.9s
+✔ Container nginx-wsgi-flask-flask-app-2    Started 0.6s
+✔ Container nginx-wsgi-flask-nginx-proxy-1  Started 1.1s
+```
+
+See the three different instances.
+
+```bash
+$ docker ps
+CONTAINER ID   IMAGE                          COMMAND                  CREATED         STATUS                            PORTS                     NAMES
+604ad97b224b   nginx-wsgi-flask-nginx-proxy   "/docker-entrypoint.…"   5 seconds ago   Up 4 seconds (health: starting)   0.0.0.0:80->80/tcp        nginx-wsgi-flask-nginx-proxy-1
+317e4d706858   nginx-wsgi-flask-flask-app     "gunicorn -w 3 -t 60…"   5 seconds ago   Up 5 seconds (health: starting)   0.0.0.0:53323->8000/tcp   nginx-wsgi-flask-flask-app-1
+39905ed2b5a0   nginx-wsgi-flask-flask-app     "gunicorn -w 3 -t 60…"   5 seconds ago   Up 4 seconds (health: starting)   0.0.0.0:53324->8000/tcp   nginx-wsgi-flask-flask-app-2
+f98baa201cb6   nginx-wsgi-flask-flask-app     "gunicorn -w 3 -t 60…"   5 seconds ago   Up 4 seconds (health: starting)   0.0.0.0:53325->8000/tcp   nginx-wsgi-flask-flask-app-3
+```
+
+Each time the url is called, nginx fowards the message to one of three instances. See container id value in the result string.
+
+``` bash
+$ curl localhost/info
+{"connecting_ip":"172.30.0.1","containe_id":"f98baa201cb6","host":"localhost","proxy_ip":"172.30.0.1","user-agent":"curl/7.79.1"}
+```
+
 ## About
 
 By following the steps above, you will have an NGINX Reverse Proxy and a Flask backend. The general traffic flow will look like the following:

nginx-wsgi-flask/compose.yaml

@@ -2,10 +2,6 @@ services:
   nginx-proxy:
     build: nginx
     restart: always
-    volumes:
-      - ./nginx/default.conf:/tmp/default.conf
-    environment: 
-      - FLASK_SERVER_ADDR=flask-app:8000
     ports:
       - "80:80"
     depends_on:
@@ -15,12 +11,12 @@ services:
       interval: 10s
       timeout: 10s
       retries: 3
-    command: /app/start.sh
+    command: nginx -g 'daemon off;'
   flask-app:
     build: flask
     restart: always
     ports: 
-      - '8000:8000'
+      - '8000'
     healthcheck:
       test: ["CMD-SHELL", "curl --silent --fail localhost:8000/flask-health-check || exit 1"]
       interval: 10s

nginx-wsgi-flask/flask/Dockerfile

@@ -26,7 +26,4 @@ ENV PATH="$VIRTUAL_ENV/bin:$PATH"
 RUN export FLASK_APP=app.py
 RUN pip install -r requirements.txt
 
-# define the port number the container should expose
-EXPOSE 5000
-
 CMD ["python", "app.py"]

nginx-wsgi-flask/flask/app.py

@@ -1,4 +1,5 @@
 from flask import Flask, request, jsonify
+import socket
 
 app = Flask(__name__)
 
@@ -17,6 +18,7 @@ def info():
 		'connecting_ip': request.headers['X-Real-IP'],
 		'proxy_ip': request.headers['X-Forwarded-For'],
 		'host': request.headers['Host'],
+		'containe_id': socket.gethostname(),
 		'user-agent': request.headers['User-Agent']
 	}
 

nginx-wsgi-flask/flask/requirements.txt

@@ -1,2 +1,2 @@
-Flask==1.1.1
-gunicorn==20.0.4
+Flask==2.3.2
+gunicorn==21.0.1

nginx-wsgi-flask/nginx/Dockerfile

@@ -5,7 +5,8 @@ RUN apk add bash
 
 # Add nginx.conf to container
 COPY --chown=nginx:nginx nginx.conf /etc/nginx/nginx.conf
-COPY --chown=nginx:nginx start.sh /app/start.sh
+COPY --chown=nginx:nginx default.conf /etc/nginx/conf.d/default.conf
+# COPY --chown=nginx:nginx start.sh /app/start.sh
 
 # set workdir
 WORKDIR /app
@@ -29,4 +30,5 @@ RUN touch /var/run/nginx.pid && chown -R nginx:nginx /var/run/nginx.pid
 
 USER nginx
 
-CMD ["nginx", "-g", "'daemon off;'"]
+# CMD ["nginx", "-g", "'daemon off;'"]
+CMD ["bash"]

nginx-wsgi-flask/nginx/default.conf

@@ -4,14 +4,14 @@ server {
   listen 80;
 
   location / {
-    proxy_pass http://$FLASK_SERVER_ADDR;
+    proxy_pass http://flask-app:8000;
     proxy_set_header Host $host;
     proxy_set_header X-Real-IP $remote_addr;
     proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
   }
 
   location /cache-me {
-    proxy_pass http://$FLASK_SERVER_ADDR;
+    proxy_pass http://flask-app:8000;
     proxy_cache cache;
     proxy_cache_lock on;
     proxy_cache_valid 200 30s;
@@ -25,5 +25,4 @@ server {
     add_header Content-Type text/plain;
     return 200 "success";
   }
-
 }

nginx-wsgi-flask/nginx/nginx.conf

@@ -46,5 +46,4 @@ http {
 	# ssl_session_tickets off;
 
     include /etc/nginx/conf.d/*.conf;
-
 }