多個tomcat之間的session複製

時間 2019-12-05

原文原文鏈接

用tomcat作負載集羣時, 常常會用到session複製(Session Replication), 不少例子會告訴咱們要配置apache或者其餘的Web Server. 而事實上, 單純從session複製的角度講, 是不須要Web Server的.javascript

tomcat的session複製分爲兩種, 一種是全局試的(all-to-all), 這意味着一個node(tomcat實例)的session發生變化以後, 它會將這些變動複製到其餘全部集羣組的成員;另外一種是局部試的, 它會用到BackupManager, BackupManager能實現只複製給一個Buckup Node, 而且這個Node會部署相同的Web應用, 可是這種方式並沒用通過不少的測試(來自官方說明..).html

tomcat的session複製是基於IP組播(multicast)來完成的, 詳細的IP組播介紹能夠參考這裏.java

簡單的說就是須要進行集羣的tomcat經過配置統一的組播IP和端口來肯定一個集羣組, 當一個node的session發生變動的時候, 它會向IP組播發送變動的數據, IP組播會將數據分發給全部組裏的其餘成員(node).node

配置以下(這裏全部的tomcat都在不一樣的物理主機, 若是在同一臺主機上須要改tomcat的tcpListenPort)web

Xml代碼apache

<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>

而後新建一個web應用, 咱們這裏叫TomcatClusterDemo, web context與名稱一致.tomcat

新建一個jsp, 這個jsp複製向session裏建立/更新屬性, 並將session裏的全部屬性顯示在網頁上. session

固然, 爲了驗證咱們的session是同步的, 咱們還將session ID顯示了出來, 代碼以下:app

Jsp代碼webapp

<%@ 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>

同時, 在web.xml裏增長<distributable/>描述

Xml代碼

<?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>