集群方式
tomcat集群一共有下面幾種方式：
- Apache Tomcat Clustering
- JWT機制
- MSM、Tomcat+Redis等統(tǒng)一Session管理
詳細
Apache Tomcat Clustering
這個是tomcat自帶的集群方式，好處是配置簡單，缺點是session共享時，使用帶寬比較高粱玲，性能比較差，適合小集群使用
配置方式
- 在server.xml中找到
<!--
<Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster"/>
-->
在下面粘貼下面內(nèi)容：
<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.ClusterSessionListener"/>
</Cluster>
這里其實沒有什么需要改的，在多個tomcat下的server.xml都粘貼上并保持一致
- 在web.xml中添加 <distributable/>標(biāo)簽
MSM
MSM是Tomcat+Memcached劳翰，使用Memcached管理session
這里有一個點要注意的就是有兩種配置方式，一種是sticky粘性配置馒疹，一種是non-sticky配置佳簸，具體區(qū)別：
non-sticky:tomcat每次都會訪問memcached
sticky:tomcat會先操作本地的Session，當(dāng)達到閾值時才會寫
優(yōu)點：通用性強
缺點：效率達不到極致
Memcached颖变，如果這個時候另一個tomcat需要Session生均，則復(fù)制session到TomcatB對應(yīng)的memcached主節(jié)點中
優(yōu)點：如果能保證同ip分配到同一個tomcat中，效率高
缺點：
1.容易造成熱點數(shù)據(jù)的訪問腥刹，大部分請求都到了同一tomcat
2.單點故障马胧，因為是先寫入本地tomcat的session，后面才回寫到memcached肛走，如果此時tomcat發(fā)生故障漓雅，沒有回寫的數(shù)據(jù)就會丟失
3.如果不能保證同一個ip同一個tomcat處理，則效率非常低
non-sticky配置
- 修改conf/Context.xml
<Manager className="de.javakaffee.web.msm.MemcachedBackupSessionManager"
memcachedNodes="n1:192.168.139.145:2222,n2:192.168.139.145:3333"
sticky="false"
sessionBackupAsync="false"
lockingMode="auto"
requestUriIgnorePattern=".*\.(ico|png|gif|jpg|css|js)$"
transcoderFactoryClass="de.javakaffee.web.msm.serializer.kryo.KryoTranscoderFactory"
/>
這里要注意的是：
1.把sticky設(shè)置成false朽色，非粘性
2.memcachedNodes就是填memcached節(jié)點地址
3.lockingMode:并發(fā)請求session時的鎖定方式邻吞，一共有四種：
none:session不被鎖定
all:session會被鎖定直到請求結(jié)束
auto:檢測到只讀請求不會鎖定，非只讀請求鎖定
uriPattern:<regexp>:如果requestURI+"?"+queryString匹配配置的表達式葫男，session將不被鎖定
4.requestUriIgnorePattern:匹配的資源將不會被session備份
- 測試結(jié)果
準(zhǔn)備兩個tomcat抱冷，部署測試代碼到tomcat中
測試代碼如下：
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>測試Session共享內(nèi)容</title>
</head>
<body>
<%
Object sessionMessage = session.getAttribute("sessionMessage");
if (sessionMessage!=null && sessionMessage.toString().trim().length()>0) {
out.println("session有值 session="+sessionMessage);
}else{
session.setAttribute("sessionMessage","Hello imooc jiangzh");
out.println("session沒有值");
}
%>
</body>
</html>
分別請求http://localhost:8080和http://localhost:8090/
sticky配置
- 修改server.xml
<!-- You should set jvmRoute to support load-balancing via AJP ie :
<Engine name="Catalina" defaultHost="localhost" jvmRoute="jvm1">
-->
<Engine name="Catalina" defaultHost="localhost" jvmRoute="jvmb">
在Engine節(jié)點中添加jvmRoute屬性，這里每個tomcat要配置不同名字梢褐，通過注釋可以知道使用了做負載均衡的
- 配置config/context.xml
<Manager className="de.javakaffee.web.msm.MemcachedBackupSessionManager"
memcachedNodes="n1:192.168.139.145:2222,n2:192.168.139.145:3333"
sticky="true"
sessionBackupAsync="false"
failoverNodes="n1"
requestUriIgnorePattern=".*\.(ico|png|gif|jpg|css|js)$"
transcoderFactoryClass="de.javakaffee.web.msm.serializer.kryo.KryoTranscoderFactory"
/>
說明：
1.sticky配置true
2.添加failoverNodes屬性旺遮，不同tomcat配置不一樣名字
failoverNodes:（這是只能用于sticky配置的）
This attribute must contain the ids of the memcached nodes that must only be used for session backup when none of the other memcached nodes are available. Therefore, you should list those memcached nodes, that are running on the same machine as this tomcat. E.g. if you have tomcat1 and memcached1 (n1) running on host1, and tomcat2 and memcached2 (n2) on host2, then you set n1 as failover node for tomcat1, so that tomcat1 does only store sessions in memcached1 if memcached2 is not available (for tomcat2 failoverNodes would be set to n2). With this setting host1 could completely crash and sessions from tomcat1 would still be available.
簡單來說就是當(dāng)memcached節(jié)點down后備份用的
- 測試
同上面non-sticky
參考
https://github.com/magro/memcached-session-manager/wiki/SetupAndConfiguration#example-for-non-sticky-sessions--kryo
http://yuanhsh.iteye.com/blog/2191934
