Docker+Nginx+tomcat模拟tomcat集群负载均衡
启动docker服务，拉取tomcat，nginx镜像
本文是基于 win10 环境进行集成，至于怎么在win10环境上体验docker,可自行百度，本文不在阐述。
安装好docker服务之后，启动docker服务，运行如下命令，拉取tomcat，nginx镜像：
docker pull hub.c.163.com/library/tomcat:latest
docker pull hub.c.163.com/library/nginx:latest
镜像拉取成功之后，运行 docker images命令查看拉取的镜像：
λ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
redis latest c5355f8853e4 4 weeks ago 107MB
hub.c.163.com/library/ubuntu latest ccc7a11d65b1 8 months ago 120MB
hub.c.163.com/library/tomcat latest 72d2be374029 8 months ago 292MB
hub.c.163.com/library/nginx latest 46102226f2fd 12 months ago 109MB
启动tomcat容器，挂载本地目录
docker run -it -p 58080:8080 -v E:\local_data\:/data --name tomcat_02 hub.c.163.com/library/tomcat /bin/bash
运行上述命令，启动容器，将宿主机的 E:\local_data\ 挂载到容器的 /data 目录下。将打包好的war包放在 E:\local_data\目录下，使用如下命令将war包复制到 tomcat 的 webapps 下，并启动tomcat。
cp /data/nginx_tomcat-0.0.1-SNAPSHOT.war /usr/local/tomcat/webapps/sh /usr/local/tomcat/bin/startup.sh
重复上述操作，连续启动三个tomcat容器，如下所示：
λ docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
175d6f2be242 hub.c.163.com/library/tomcat "/bin/bash" 7 hours ago Up 7 hours 0.0.0.0:48080->8080/tcp tomcat_03
11d5b4487c66 hub.c.163.com/library/tomcat "/bin/bash" 7 hours ago Up 7 hours 0.0.0.0:38080->8080/tcp tomcat_02
c77cd2b2a6e9 hub.c.163.com/library/tomcat "/bin/bash" 7 hours ago Up 7 hours 0.0.0.0:58080->8080/tcp tomcat_01
启动nginx并配置
docker run -p 80:80 --privileged=true -v E:\my_nginx\config\nginx.conf:/etc/nginx/nginx.conf --name mynginx hub.c.163.com/library/nginx
将nginx的80端口映射到宿主机的80端口，将宿主机的 E:\my_nginx\config\nginx.conf 目录挂载到容器的 /etc/nginx/nginx.conf 目录下，用自定义 nginx.conf配置文件覆盖默认配置文件。
配置文件如下所示：
user nginx;
worker_processes 1;
error_log /var/log/nginx/error.log warn;
pid /var/run/nginx.pid;
events {
worker_connections 1024;
}
http {
server {
listen 80;
location / {
proxy_pass http://blance;
}
}
upstream blance{
server 172.17.0.2:8080;
server 172.17.0.3:8080;
server 172.17.0.4:8080;
}
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;
}
其中，以下为在默认配置内容中新增的内容
server {
listen 80;
location / {
proxy_pass http://blance;
}
}
upstream blance{
server 172.17.0.2:8080;
server 172.17.0.3:8080;
server 172.17.0.4:8080;
}
运行启动命令，启动nginx容器。
查看所有启动容器，测试是否均衡负载
运行 docker ps 命令查看所有正在运行的容器：
λ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
b0d477164bed hub.c.163.com/library/nginx "nginx -g 'daemon of…" 35 minutes ago Up 35 minutes 0.0.0.0:80->80/tcp mynginx
175d6f2be242 hub.c.163.com/library/tomcat "/bin/bash" 7 hours ago Up 7 hours 0.0.0.0:48080->8080/tcp tomcat_03
11d5b4487c66 hub.c.163.com/library/tomcat "/bin/bash" 7 hours ago Up 7 hours 0.0.0.0:38080->8080/tcp tomcat_02
c77cd2b2a6e9 hub.c.163.com/library/tomcat "/bin/bash" 7 hours ago Up 7 hours 0.0.0.0:58080->8080/tcp tomcat_01
浏览器访问 127.0.0.1:80 ，进入tomcat 欢迎页面。
多次访问 127.0.0.1/nginx_tomcat-0.0.1-SNAPSHOT/test/loadBalancing 链接，会打印请求到的服务的ip及端口，
java代码如下：
/**
* Created by Haiyoung on 2018/5/1.
*/@RestController@RequestMapping( value = "/test")public class LoadBalancing {
@RequestMapping( value = "/loadBalancing")
public String loadBalancingTest(HttpServletRequest request) throws UnknownHostException {
String ip = java.net.InetAddress.getLocalHost().getHostAddress();
int post = request.getLocalPort();
System.out.println(ip + ":" + post);
return ip + ":" + post;
}}
请求结果如下所示：
172.17.0.2:8080
172.17.0.3:8080
172.17.0.4:8080
172.17.0.2:8080
172.17.0.3:8080
172.17.0.4:8080
172.17.0.2:8080
可见，nginx实现了对请求的负载均衡。
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