nginx+tomcat负载均衡

本文使用到nginx1.5.4、tomcat6.0.35。

1、配置nginx

~/conf/nginx.conf

#user  guzicheng;
worker_processes  1;

error_log  logs/error.log;
#error_log  logs/error.log  notice;
#error_log  logs/error.log  info;

#pid        logs/nginx.pid;


events {
    worker_connections  1024;
}


http {
    include       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  logs/access.log  main;

    sendfile        on;
    #tcp_nopush     on;

    #keepalive_timeout  0;
    keepalive_timeout  65;

    gzip  on;

    upstream localhost {
	server 127.0.0.1:8081;
	server 127.0.0.1:8082;
    }

    server {
        listen       80;
        server_name  localhost;

        charset utf-8;

        #access_log  logs/host.access.log  main;

        location / {
            root   html;
            index  index.html index.htm;
            proxy_pass http://localhost; 
        }

        #error_page  404              /404.html;

        # redirect server error pages to the static page /50x.html
        #
        error_page   500 502 503 504  /50x.html;
        location = /50x.html {
            root   html;
        }

        # proxy the PHP scripts to Apache listening on 127.0.0.1:80
        #
        #location ~ \.php$ {
        #    proxy_pass   http://127.0.0.1;
        #}

        # pass the PHP scripts to FastCGI server listening on 127.0.0.1:9000
        #
        #location ~ \.php$ {
        #    root           html;
        #    fastcgi_pass   127.0.0.1:9000;
        #    fastcgi_index  index.php;
        #    fastcgi_param  SCRIPT_FILENAME  /scripts$fastcgi_script_name;
        #    include        fastcgi_params;
        #}

        # deny access to .htaccess files, if Apache's document root
        # concurs with nginx's one
        #
        #location ~ /\.ht {
        #    deny  all;
        #}
    }


    # another virtual host using mix of IP-, name-, and port-based configuration
    #
    #server {
    #    listen       8000;
    #    listen       somename:8080;
    #    server_name  somename  alias  another.alias;

    #    location / {
    #        root   html;
    #        index  index.html index.htm;
    #    }
    #}


    # HTTPS server
    #
    #server {
    #    listen       443 ssl;
    #    server_name  localhost;

    #    ssl_certificate      cert.pem;
    #    ssl_certificate_key  cert.key;

    #    ssl_session_cache    shared:SSL:1m;
    #    ssl_session_timeout  5m;

    #    ssl_ciphers  HIGH:!aNULL:!MD5;
    #    ssl_prefer_server_ciphers  on;

    #    location / {
    #        root   html;
    #        index  index.html index.htm;
    #    }
    #}

}

主要修改内容：

……

http{

    upstream localhost {
       server 127.0.0.1:8081;
       server 127.0.0.1:8082;
    }

    server {
        listen       80;
        server_name  localhost;

        ……

        location / {
            ……
            proxy_pass http://localhost; 
        }

        ……

     }
}

……

测试修改内容：

/usr/local/nginx/sbin/nginx -t

启动nginx

/usr/local/nginx/sbin/nginx

在浏览器中输入http://localhost，测试nginx是否启动成功。

2、配置Tomcat

分别打开tomcat1和tomcat2下conf中server.xml。

注意端口号不要重复

<Server port="8005" shutdown="SHUTDOWN">
...
<Connector port="8081" protocol="HTTP/1.1" 
               connectionTimeout="20000" 
               redirectPort="8443" />
...
<!-- Define an AJP 1.3 Connector on port 8009 -->
    <Connector port="8009" protocol="AJP/1.3" redirectPort="8443" />

修改<Engine>节点

<Engine name="Catalina" defaultHost="localhost" jvmRoute="tomcat1">

<Engine name="Catalina" defaultHost="localhost"jvmRoute="tomcat2">

（注：至此，完成了tomcat负载均衡。下面进行session同步配置，通过tomcat自身实现session同步。）

去掉<Cluster>节点的注释

<Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster"/>

3、配置web应用

打开web.xml，在</web-app>节点前添加：

<distributable/>

到此，简单的负载均衡、session同步配置完毕。测试：

a、在tomcat下创建test工程，分别建立测试页面index.jsp

  tomcat1:

SessionID:<%=session.getId()%>  
<BR>  
SessionIP:<%=request.getServerName()%>  
<BR>  
SessionPort:<%=request.getServerPort()%>  
<BR>  
<%
    String name=(String)session.getAttribute("name");
    if(name==null||name.equals("")){
	session.setAttribute("name","Hello Host1!"); 
	out.println(session.getAttribute("name"));
    }else{
	out.println(name);
    }
%>
<BR>  
This is Tomcat Server 111111！

  tomcat2:

SessionID:<%=session.getId()%>  
<BR>  
SessionIP:<%=request.getServerName()%>  
<BR>  
SessionPort:<%=request.getServerPort()%>
<BR>  
<%
    String name=(String)session.getAttribute("name");
    if(name==null||name.equals("")){
	session.setAttribute("name","Hello Host2!"); 
	out.println(session.getAttribute("name"));
    }else{
	out.println(name);
    }
%>  
<BR>  
This is Tomcat Server 222222！

b、启动tomcat1、tomcat2、nginx

c、在浏览器中输入http://localhost/test/index.jsp

如果SessionID、CreateTime、“Hello Host”不变，最后易行“This is Tomcat Server ...”不停变化，说明session复制成功。

这种方式实现的session同步存在缺陷：当一个节点的session数据发生变化，要把整个session数据全部序列化，广播给其他节点，造成大量网络通信，导致网络阻塞。下面一篇介绍通过terracotta实现tomcat集群的session同步。

参考：

http://www.blogjava.net/Alpha/archive/2011/06/21/352745.html

http://blog.csdn.net/shimiso/article/details/8979044

http://blog.163.com/comfort_122/blog/static/48904409201131145149530