NGINX Doesn't communicate with flask rest API. Docker

This should work:

docker-compose.yml

# Run docker-compose upversion: '3'services:  nginx_demo:    image: nginx:1.13.7-alpine    container_name: nginx    restart: always    build:      context: .      dockerfile: ./Nginx/Dockerfile    volumes:      - ./Client/dist:/usr/share/nginx/html    ports:      - "80:80"    depends_on:      - flask_api    links:      - flask_api  flask_api:    container_name: flask_api    restart: always    build:      context: .      dockerfile: ./Server/Dockerfile    volumes:      - ./Server:/usr/src/app

Nginx/Dockerfile

FROM nginx:1.13.7-alpine# remove the old nginx.confRUN rm /etc/nginx/nginx.conf# Copy custom nginx configCOPY ./Nginx/nginx.conf /etc/nginx/nginx.confCOPY ./Client/dist /usr/share/nginx/htmlEXPOSE 80

Server/Dockerfile

FROM python:3.6-alpineADD ./Server /appWORKDIR /appRUN pip install -r requirements.txtEXPOSE 5000CMD ["python", "api.py"]

Nginx/nginx.conf

user  nginx;worker_processes  1;error_log  /var/log/nginx/error.log warn;pid        /var/run/nginx.pid;events {  worker_connections  1024;}http {  include       /etc/nginx/mime.types;  default_type  application/octet-stream;  log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '                    '$status $body_bytes_sent "$http_referer" '                    '"$http_user_agent" "$http_x_forwarded_for"';  access_log  /var/log/nginx/access.log  main;  sendfile    on;  keepalive_timeout  65;  gzip  on;  # Configuration for the server  server {    listen 80;    location /api {      proxy_pass http://flask_api:5000;    }    location / {      root   /usr/share/nginx/html;      index  index.html;      expires -1;      add_header Pragma "no-cache";      add_header Cache-Control "no-store, no-cache, must-revalidate, post-check=0, pre-check=0";      try_files $uri$args $uri$args/ $uri $uri/ =404;    }  }}