参考：https://www.cnblogs.com/JulianHuang/p/12568814.html

    单台机器，多实例，场景还没遇到过，先记一下吧。

    原理：利用nginx和docker内置DNS转发web接口。

    1. version: "3"
    2. services:
    3.   webapp:
    4.     image: "luksa/kubia"
    5.     depends_on:
    6.       - db
    7.     ports:
    8.       - "8080"    # 主机Port: 容器暴露Port

    nginx.conf

    1. user  nginx;
    2. events {
    3.     worker_connections   1000;
    4. }
    5. http {
    6.         server {
    7.               listen 80;
    8.               location / {
    9.                 proxy_pass http://webapp:8080;
    10.               }
    11.         }
    12. }
    1. version: "3"
    2. services:
    3.   webapp:
    4.     image: "luksa/kubia"
    5.   nginx:
    6.     image: nginx:latest
    7.     volumes:
    8.       - type: bind
    9.         source: /home/root/test/nginx.conf
    10.         target: /etc/nginx/nginx.conf
    11.     depends_on:
    12.       - webapp
    13.     ports:
    14.       - "80:80"

    :::info docker-compose up —scale webapp=3 :::

    1. IMAGE            COMMAND                  PORTS                     NAMES
    2. luksa/kubia      "node app.js"                                      test_webapp_1
    3. luksa/kubia      "node app.js"                                      test_webapp_3
    4. luksa/kubia      "node app.js"                                      test_webapp_2
    5. nginx:latest     "nginx -g 'daemon of…"   0.0.0.0:80->80/tcp      test_nginx_1