利用nginx和两个tomcat容器
nginx映射8181端口，tomcat分别映射9191和9292端口。
（关闭firewalld等服务。本机地址为192.168.200.104，docker私有仓库）

创建不同的主页来区分这两个tomcat容器。

[root@server ~]# echo "this tomcat1 port:9191" > tomcat1/index.html
[root@server ~]# echo "this tomcat2 port:9292" > tomcat2/index.html   
[root@server ~]# cat tomcat1/index.html 
this tomcat1 port:9191
[root@server ~]# cat tomcat2/index.html  
this tomcat2 port:9292

配置nginx负载均衡器：（nginx默认端口80）

[root@server ~]# docker run -dit --name nginx -p 8181:80 192.168.200.104:5000/nginx:latest 
98a219645301e873f8960277faace72303301b244f233f0bba5ee42ce2dfd573

复制nginx配置文件到宿主机：

[root@server ~]# docker cp nginx:/etc/nginx/nginx.conf .

在http{}下添加：upstream server项和server项。

[root@server ~]# cat 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;
    #tcp_nopush     on;

    keepalive_timeout  65;

    #gzip  on;

    include /etc/nginx/conf.d/*.conf;
    upstream server{
                server 192.168.200.104:9191;
                server 192.168.200.104:9292;（负载均衡列表）
                }
    server {
        listen 80;（nginx监控端口）
        server_name 192.168.200.104;（接管的访问地址）
        location / {
                        proxy_pass http://server;
                        root html;
                        index index.html index.htm;
                        }
                }
    }

将配置文件复制到nginx容器，然后重启容器：

[root@server ~]# docker cp nginx.conf nginx:/etc/nginx/
[root@server ~]# docker restart nginx
nginx
[root@server ~]# docker ps | grep nginx
98a219645301        192.168.200.104:5000/nginx:latest                     "nginx -g 'daemon off"   9 minutes ago       Up 6 seconds        0.0.0.0:8181->80/tcp               nginx

分别运行两个tomcat容器：（tomcat的默认端口是8080）

[root@server ~]# docker run -dit --name tomcat1 -v /root/tomcat1/:/usr/local/tomcat/webapps/ROOT  -p 9191:8080 192.168.200.104:5000/tomcat:latest             
b300bfea2a972c756062c03c9813781ce18579a7ba8a620d80cee9ddc3c37a38
[root@server ~]# docker exec -it tomcat1 bash
root@b300bfea2a97:/usr/local/tomcat# sh bin/startup.sh 
Tomcat started.

[root@server ~]# docker run -dit --name tomcat2 -v /root/tomcat2/:/usr/local/tomcat/webapps/ROOT  -p 9292:8080 192.168.200.104:5000/tomcat:latest     
a681d7e3ea3b8f1b0f9c899a945fa43ea080d83c99f8ba61431e9f8fef1cef07
[root@server ~]# docker exec -it tomcat2 bash
root@a681d7e3ea3b:/usr/local/tomcat# sh bin/startup.sh 
Tomcat started.

访问nginx端口（等容器完全启动后）：

[root@server ~]# curl http://192.168.200.104:8181
this tomcat1 port:9191
[root@server ~]# curl http://192.168.200.104:8181
this tomcat2 port:9292

over！