多个tomcat之间的session复制

   

用tomcat做负载集群时, 经常会用到session复制(Session Replication), 很多例子会告诉我们要配置apache或者其他的Web Server. 而事实上, 单纯从session复制的角度讲, 是不需要Web Server的.

tomcat的session复制分为两种, 一种是全局试的(all-to-all), 这意味着一个node(tomcat实例)的session发生变化之后, 它会将这些变更复制到其他所有集群组的成员;另一种是局部试的, 它会用到BackupManager, BackupManager能实现只复制给一个Buckup Node, 并且这个Node会部署相同的Web应用, 但是这种方式并没用经过很多的测试(来自官方说明..).

tomcat的session复制是基于IP组播(multicast)来完成的, 详细的IP组播介绍可以参考这里.

简单的说就是需要进行集群的tomcat通过配置统一的组播IP和端口来确定一个集群组, 当一个node的session发生变更的时候, 它会向IP组播发送变更的数据, IP组播会将数据分发给所有组里的其他成员(node).

配置如下(这里所有的tomcat都在不同的物理主机, 如果在同一台主机上需要改tomcat的tcpListenPort)

<Cluster  className="org.apache.catalina.ha.tcp.SimpleTcpCluster"
                 channelSendOptions="8">

          <Manager className="org.apache.catalina.ha.session.DeltaManager"
                   expireSessionsOnShutdown="false"
                   notifyListenersOnReplication="true"/>

          <Channel className="org.apache.catalina.tribes.group.GroupChannel">
            <Membership className="org.apache.catalina.tribes.membership.McastService"
                        address="228.0.0.4"
                        port="45564"
                        frequency="500"
                        dropTime="3000"/>
            <Receiver className="org.apache.catalina.tribes.transport.nio.NioReceiver"
                      address="auto"
                      port="4000"
                      autoBind="100"
                      selectorTimeout="5000"
                      maxThreads="6"/>

            <Sender className="org.apache.catalina.tribes.transport.ReplicationTransmitter">
              <Transport className="org.apache.catalina.tribes.transport.nio.PooledParallelSender"/>
            </Sender>
            <Interceptor className="org.apache.catalina.tribes.group.interceptors.TcpFailureDetector"/>
            <Interceptor className="org.apache.catalina.tribes.group.interceptors.MessageDispatch15Interceptor"/>
          </Channel>

          <Valve className="org.apache.catalina.ha.tcp.ReplicationValve"
                 filter=""/>
          <Valve className="org.apache.catalina.ha.session.JvmRouteBinderValve"/>

          <Deployer className="org.apache.catalina.ha.deploy.FarmWarDeployer"
                    tempDir="/tmp/war-temp/"
                    deployDir="/tmp/war-deploy/"
                    watchDir="/tmp/war-listen/"
                    watchEnabled="false"/>

          <ClusterListener className="org.apache.catalina.ha.session.JvmRouteSessionIDBinderListener"/>
          <ClusterListener className="org.apache.catalina.ha.session.ClusterSessionListener"/>
        </Cluster>

<Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster"
                 channelSendOptions="8">

          <Manager className="org.apache.catalina.ha.session.DeltaManager"
                   expireSessionsOnShutdown="false"
                   notifyListenersOnReplication="true"/>

          <Channel className="org.apache.catalina.tribes.group.GroupChannel">
            <Membership className="org.apache.catalina.tribes.membership.McastService"
                        address="228.0.0.4"
                        port="45564"
                        frequency="500"
                        dropTime="3000"/>
            <Receiver className="org.apache.catalina.tribes.transport.nio.NioReceiver"
                      address="auto"
                      port="4000"
                      autoBind="100"
                      selectorTimeout="5000"
                      maxThreads="6"/>

            <Sender className="org.apache.catalina.tribes.transport.ReplicationTransmitter">
              <Transport className="org.apache.catalina.tribes.transport.nio.PooledParallelSender"/>
            </Sender>
            <Interceptor className="org.apache.catalina.tribes.group.interceptors.TcpFailureDetector"/>
            <Interceptor className="org.apache.catalina.tribes.group.interceptors.MessageDispatch15Interceptor"/>
          </Channel>

          <Valve className="org.apache.catalina.ha.tcp.ReplicationValve"
                 filter=""/>
          <Valve className="org.apache.catalina.ha.session.JvmRouteBinderValve"/>

          <Deployer className="org.apache.catalina.ha.deploy.FarmWarDeployer"
                    tempDir="/tmp/war-temp/"
                    deployDir="/tmp/war-deploy/"
                    watchDir="/tmp/war-listen/"
                    watchEnabled="false"/>

          <ClusterListener className="org.apache.catalina.ha.session.JvmRouteSessionIDBinderListener"/>
          <ClusterListener className="org.apache.catalina.ha.session.ClusterSessionListener"/>
        </Cluster>

然后新建一个web应用, 我们这里叫TomcatClusterDemo, web context与名称一致.

新建一个jsp, 这个jsp复制向session里创建/更新属性, 并将session里的所有属性显示在网页上.

当然, 为了验证我们的session是同步的, 我们还将session ID显示了出来, 代码如下:

  <%@ page contentType="text/html; charset=UTF-8" %>
<%@ page import="java.util.*" %>
<html><head><title>Tomcat Cluster Demo</title></head>
<body>
Server Info:
<%
out.println(request.getLocalAddr() + " : " + request.getLocalPort()+"<br>");%>
<%
  out.println("<br> ID " + session.getId()+"<br>");

  String dataName = request.getParameter("dataName");
  if (dataName != null && dataName.length() > 0) {
     String dataValue = request.getParameter("dataValue");
     session.setAttribute(dataName, dataValue);
     System.out.println("application:" + application.getAttribute(dataName));
     application.setAttribute(dataName, dataValue);
  }
  out.print("<b>Session List</b>");
  Enumeration<String> e = session.getAttributeNames();
  while (e.hasMoreElements()) {
     String name = e.nextElement();
     String value = session.getAttribute(name).toString();
     out.println( name + " = " + value+"<br>");
         System.out.println( name + " = " + value);
   }
%>
  <form action="test.jsp" method="POST">
    Name:<input type=text size=20 name="dataName">
     <br>
    Value:<input type=text size=20 name="dataValue">
     <br>
    <input type=submit>
   </form>
</body>
</html>

  <%@ page contentType="text/html; charset=UTF-8" %>
<%@ page import="java.util.*" %>
<html><head><title>Tomcat Cluster Demo</title></head>
<body>
Server Info:
<%
out.println(request.getLocalAddr() + " : " + request.getLocalPort()+"<br>");%>
<%
  out.println("<br> ID " + session.getId()+"<br>");
  
  String dataName = request.getParameter("dataName");
  if (dataName != null && dataName.length() > 0) {
     String dataValue = request.getParameter("dataValue");
     session.setAttribute(dataName, dataValue);
     System.out.println("application:" + application.getAttribute(dataName));
     application.setAttribute(dataName, dataValue);
  }
  out.print("<b>Session List</b>");
  Enumeration<String> e = session.getAttributeNames();
  while (e.hasMoreElements()) {
     String name = e.nextElement();
     String value = session.getAttribute(name).toString();
     out.println( name + " = " + value+"<br>");
         System.out.println( name + " = " + value);
   }
%>
  <form action="test.jsp" method="POST">
    Name:<input type=text size=20 name="dataName">
     <br>
    Value:<input type=text size=20 name="dataValue">
     <br>
    <input type=submit>
   </form>
</body>
</html>

同时, 在web.xml里增加<distributable/>描述

<?xml  version="1.0" encoding="UTF-8"?>
<web-app  id="WebApp_ID" version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
    <display-name>TomcatClusterDemo</display-name>
    <distributable/>
    <welcome-file-list>
        <welcome-file>index.html</welcome-file>
        <welcome-file>index.htm</welcome-file>
        <welcome-file>index.jsp</welcome-file>
        <welcome-file>default.html</welcome-file>
        <welcome-file>default.htm</welcome-file>
        <welcome-file>test.jsp</welcome-file>
    </welcome-file-list>
</web-app>

<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_ID" version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
	<display-name>TomcatClusterDemo</display-name>
	<distributable/>
	<welcome-file-list>
		<welcome-file>index.html</welcome-file>
		<welcome-file>index.htm</welcome-file>
		<welcome-file>index.jsp</welcome-file>
		<welcome-file>default.html</welcome-file>
		<welcome-file>default.htm</welcome-file>
		<welcome-file>test.jsp</welcome-file>
	</welcome-file-list>
</web-app>

现在将TomcatClusterDemo部署到两个tomcat上(直接将war包或者部署文件拷贝到webapps下, 或者通过Tomcat Web Application Manager部署), 依次启动两个tomcat.

先访问第一台tomcat(下面的9.119.84.68)的test.jsp, 并添加几个session.

然后访问第二台tomcat(下面的9.119.84.88)的test.jsp, 为了告诉tomcat我们要用那个session访问, 我们需要在URL后面加上 ;jsessionid=SESSION_ID

SESSION_ID可以从第一个test.jsp页面上获得.

看看效果, 两个在不同server上的tomcat实现了session复制!