问题背景

在docker里用同一份镜像创建4个容器，网络选择bridge模式，A服务在四个容器中都使用了同一个端口号（6000）；为了减少对外暴露的端口数，另外使用了nginx对这4个服务实例做代理，4个服务实例分属4个upstream，使用了类似/service1、/service2的路径来访问4个实例。此时从本地访问任一服务，则会报502错误，百思不得其解。

connect() failed (111: Connection refused) while connecting to upstream

compose文件

version: '2'
networks:
  nn:
    driver: bridge
services:
  service-1:
    container_name: service-1
    image: foo
    networks:
      - nn
    volumes:
      - ./logs/1:/apps/aaa/bbb-logs
      - ./common:/apps/aaa/bbb
      - ./xxx/1.xml:/ccc/targets.xml
    entrypoint: foo.sh
    command: start app=foo port=6000
    
  service-2:
    container_name: service-2
    image: foo
    networks:
      - nn
    volumes:
      - ./logs/2:/apps/aaa/bbb-logs
      - ./common:/apps/aaa/bbb
      - ./xxx/2.xml:/ccc/targets.xml
    entrypoint: foo.sh
    command: start app=foo port=6000
  
  service-3:
    container_name: service-3
    image: foo
    networks:
      - nn
    volumes:
      - ./logs/3:/apps/aaa/bbb-logs
      - ./common:/apps/aaa/bbb
      - ./xxx/3.xml:/ccc/targets.xml
    entrypoint: foo.sh
    command: start app=foo port=6000

  service-4:
    container_name: service-4
    image: foo
    networks:
      - nn
    volumes:
      - ./logs/4:/apps/aaa/bbb-logs
      - ./common:/apps/aaa/bbb
      - ./xxx/4.xml:/ccc/targets.xml
    entrypoint: foo.sh
    command: start app=foo port=6000    

  nginx:
    container_name: nginx
    image: nginx:1.15-alpine
    ports:
      - 6001:6001
    networks:
      - nn
    volumes:
      - ./nginx/nginx.conf:/etc/nginx/nginx.conf
      - ./logs/nginx:/var/log/nginx

nginx.conf

worker_processes 8;
worker_rlimit_nofile 65535;

events {
        use epoll;
        worker_connections  65535;
 }

http {
        include mime.types;
        default_type aplication/octet-stream;
        sendfile on;
        log_format main '[$time_local]$remote_addr-$upstream_addr "$request" $status  $body_bytes_sent';


        upstream service1.local {
            server service-1:6000;
        }
        upstream service2.local {
          server service-2:6000;
        }
        upstream service3.local {
            server service-3:6000;
        }
        upstream service4.local {
            server service-4:6000;
        }

        server {
            listen 6001;
            client_max_body_size 100M;
            proxy_set_header Host $host:$server_port;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;

            location /service1/ {
                proxy_pass http://service1.local/;
            }
            location /service2/ {
                proxy_pass http://service2.local/;
            }
            location /service3/ {
                proxy_pass http://service3.local/;
            }
            location /service4/ {
                proxy_pass http://service4.local/;
            }
            location /nginx_status {
                stub_status on;
                access_log off;
            }
        }
}

此时curl localhost:6001/service1/api/v1/....就会报上面的502错误，按理说每一个容器都是有各自的网卡，不同容器的端口号应该不冲突才对。

解决方案

暂时没有较好的方案，只能对4个服务使用不同的端口号，nginx也相应地修改。