Tomcat Redis 實(shí)現(xiàn)簡(jiǎn)單的session集群

目前負(fù)載的處理方案

1.IP HASH CODE強(qiáng)制指定機(jī)器

在ngnix中配置IP HashCode 指定的IP永遠(yuǎn)會(huì)Hash到指定的一臺(tái)機(jī)器上，前提假定的是，用戶在一次會(huì)話中
，IP地址不會(huì)改變，那么用戶的會(huì)話信息存儲(chǔ)在一臺(tái)機(jī)器上，并且用戶的所有請(qǐng)求都反向代理到這臺(tái)機(jī)器上，但是此方法有一個(gè)
很致命的弊端，就是用戶的網(wǎng)絡(luò)狀態(tài)不會(huì)發(fā)生改變，舉例：若手機(jī)用戶訪問(wèn)網(wǎng)頁(yè)，期間由4G網(wǎng)絡(luò)切換帶了WIFI網(wǎng)絡(luò)下，那么就會(huì)造成
實(shí)際處理請(qǐng)求的機(jī)器發(fā)生改變，會(huì)話信息發(fā)生變動(dòng)而出現(xiàn)問(wèn)題。

2.Session同步

將多臺(tái)web服務(wù)器的session信息保存在一處公共區(qū)域，如：數(shù)據(jù)庫(kù)，緩存中間件等（redis，memcache）,適合中小規(guī)模的集群選擇
，用戶的session存取信息全部存儲(chǔ)在NOSQL的KEY-VALUE數(shù)據(jù)庫(kù)中(本文將重點(diǎn)介紹)，但是

3.Session加密放入Cookie中

將會(huì)話信息進(jìn)行對(duì)稱加密放進(jìn)Cookie中，優(yōu)點(diǎn)是不用將信息放在服務(wù)器中去考慮中間件存儲(chǔ)Session單點(diǎn)故障問(wèn)題，但是對(duì)于
會(huì)話信息的管理非常嚴(yán)格，因?yàn)镃ookie存儲(chǔ)的信息長(zhǎng)度有限。目前大廠基本都是用的cookie存儲(chǔ)會(huì)話信息

Tomcat Redis Session共享配置

準(zhǔn)備Jar包:

1.jedis-2.2.1.jar
2.tomcat-redis-session-manager-1.2-tomcat-7-1.2.jar (此Jar包生成方法下文會(huì)提到)
3.commons-pool-1.6.jar

將上述Jar包放置于tomcat的共享lib目錄下，修改tomcat的CONF下的content.xml的文件內(nèi)容如下

<?xml version="1.0" encoding="UTF-8"?>
    <WatchedResource>WEB-INF/web.xml</WatchedResource>
    <Valve className="com.radiadesign.catalina.session.RedisSessionHandlerValve"/>
    <Manager className="com.radiadesign.catalina.session.RedisSessionManager"
         host="0.0.0.0"<!-- 自行設(shè)定redis地址 -->
         port="6379"
         database="0"
         password="******"
         maxInactiveInterval="60"/>
</Context>

下面建立兩個(gè)JavaEE工程,啟動(dòng)兩個(gè)tomcat并配置相同的context.xml信息，使用ngnix做負(fù)載均衡,ngnix的配置信息如下

#user  nobody;
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;
    client_max_body_size 300M;

    sendfile        on;

    keepalive_timeout  200;

    upstream redis-sync {
      server 127.0.0.1:8081;
      server 127.0.0.1:8080;
    }

    server {
        listen       80;
        server_name  localhost;

        #charset koi8-r;

        #access_log  logs/host.access.log  main;

        location /redis-sync {
            proxy_set_header  Host $host;
            proxy_set_header  X-Real-IP  $remote_addr;
            proxy_pass  http://redis-sync;
        }
    }
}

新建一個(gè)servlet信息

package com.charles.servlet;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class SessionSyncServlet
 */
@WebServlet(name = "SessionSync", urlPatterns = "/SessionSync")
public class SessionSyncServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public SessionSyncServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
    //一個(gè)項(xiàng)目寫session，一個(gè)項(xiàng)目讀session
    //request.getSession().setAttribute("sessionSync", "I have written");
    //response.getWriter().write("A have written");
        Object obj = request.getSession().getAttribute("sessionSync");
        String out;
        if (obj != null) {
            out = "B Have getten session "obj.toString();
        } else {
            out = "null Session";
        }
        response.getWriter().write(out);
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
    }

}

訪問(wèn)地址http://localhost/redis-sync/SessionSync
會(huì)交替出現(xiàn)

A have written
B Have getten session I have written

附錄：補(bǔ)充 redis-session-tomcat 打包方式
http://blog.jobbole.com/71999/ 里有詳細(xì)介紹