前言
在Tomcat集群中，当一个节点出现故障，其他节点该如何接管故障节点的Session信息呢？本文带来的解决方案是基于MSM+Memcached实现Session共享。
相关介绍
MSM
MSM--Memcached Session Manager是一个高可用的Tomcat Session共享解决方案，除了可以从本机内存快速读取Session信息(仅针对黏性Session)外，同时可使用Memcached存取Session，以实现高可用。
工作原理
Sticky Session（黏性） 模式下的工作原理
#Tomcat本地Session为主Session，Memcached 中的Session为备Session
安装在Tomcat上的MSM使用本机内存保存Session，当一个请求执行完毕之后，如果对应的Session在本地不存在（即某用户的第一次请求），则将该Session复制一份至Memcached；当该Session的下一个请求到达时，会使用Tomcat的本地Session，请求处理结束之后，Session的变化会同步更新到 Memcached，保证数据一致。
当集群中的一个Tomcat挂掉，下一次请求会被路由到其他Tomcat上。负责处理此此请求的Tomcat并不清楚Session信息，于是从Memcached查找该Session，更新该Session并将其保存至本机。此次请求结束，Session被修改，送回Memcached备份。
Non-sticky Session （非黏性）模式下的工作原理
#Tomcat本地Session为中转Session，Memcached为主备Session
收到请求，加载备Session至本地容器，若备Session加载失败则从主Session加载
请求处理结束之后，Session的变化会同步更新到Memcached，并清除Tomcat本地Session
实现过程
实验拓扑
#系统环境：CentOS6.6
nginx安装配置
#解决依赖关系 [[email protected] ~]# yum groupinstall "Development Tools" "Server Platform Deveopment" -y [[email protected] ~]# yum install openssl-devel pcre-devel -y [[email protected] ~]# groupadd -r nginx [[email protected] ~]# useradd -r -g nginx nginx [[email protected] ~]# tar xf nginx-1.6.3.tar.gz [[email protected] ~]# cd nginx-1.6.3 [[email protected] nginx-1.6.3]# ./configure > --prefix=/usr/local/nginx > --sbin-path=/usr/sbin/nginx > --conf-path=/etc/nginx/nginx.conf > --error-log-path=/var/log/nginx/error.log > --http-log-path=/var/log/nginx/access.log > --pid-path=/var/run/nginx/nginx.pid > --lock-path=/var/lock/nginx.lock > --user=nginx > --group=nginx > --with-http_ssl_module > --with-http_flv_module > --with-http_stub_status_module > --with-http_gzip_static_module > --http-client-body-temp-path=/usr/local/nginx/client/ > --http-proxy-temp-path=/usr/local/nginx/proxy/ > --http-fastcgi-temp-path=/usr/local/nginx/fcgi/ > --http-uwsgi-temp-path=/usr/local/nginx/uwsgi > --http-scgi-temp-path=/usr/local/nginx/scgi > --with-pcre [[email protected] nginx-1.6.3]# make && make install
为nginx提供SysV init脚本
[[email protected] ~]# vim /etc/rc.d/init.d/nginx
#新建文件/etc/rc.d/init.d/nginx，内容如下：
#!/bin/sh
#
# nginx - this script starts and stops the nginx daemon
#
# chkconfig: - 85 15
# description: Nginx is an HTTP(S) server, HTTP(S) reverse # proxy and IMAP/POP3 proxy server
# processname: nginx
# config: /etc/nginx/nginx.conf
# config: /etc/sysconfig/nginx
# pidfile: /var/run/nginx.pid
# Source function library.
. /etc/rc.d/init.d/functions
# Source networking configuration.
. /etc/sysconfig/network
# Check that networking is up.
[ "$NETWORKING" = "no" ] && exit 0
nginx="/usr/sbin/nginx"
prog=$(basename $nginx)
NGINX_CONF_FILE="/etc/nginx/nginx.conf"
[ -f /etc/sysconfig/nginx ] && . /etc/sysconfig/nginx
lockfile=/var/lock/subsys/nginx
make_dirs() {
# make required directories
user=`nginx -V 2>&1 | grep "configure arguments:" | sed ‘s/[^*]*--user=\([^ ]*\).*/\1/g‘ -`
options=`$nginx -V 2>&1 | grep ‘configure arguments:‘`
for opt in $options; do
if [ `echo $opt | grep ‘.*-temp-path‘` ]; then
value=`echo $opt | cut -d "=" -f 2`
if [ ! -d "$value" ]; then
# echo "creating" $value
mkdir -p $value && chown -R $user $value
fi
fi
done
}
start() {
[ -x $nginx ] || exit 5
[ -f $NGINX_CONF_FILE ] || exit 6
make_dirs
echo -n $"Starting $prog: "
daemon $nginx -c $NGINX_CONF_FILE
retval=$?
echo
[ $retval -eq 0 ] && touch $lockfile
return $retval
}
stop() {
echo -n $"Stopping $prog: "
killproc $prog -QUIT
retval=$?
echo
[ $retval -eq 0 ] && rm -f $lockfile
return $retval
}
restart() {
configtest || return $?
stop
sleep 1
start
}
reload() {
configtest || return $?
echo -n $"Reloading $prog: "
killproc $nginx -HUP
RETVAL=$?
echo
}
force_reload() {
restart
}
configtest() {
$nginx -t -c $NGINX_CONF_FILE
}
rh_status() {
status $prog
}
rh_status_q() {
rh_status >/dev/null 2>&1
}
case "$1" in
start)
rh_status_q && exit 0
$1
;;
stop)
rh_status_q || exit 0
$1
;;
restart|configtest)
$1
;;
reload)
rh_status_q || exit 7
$1
;;
force-reload)
force_reload
;;
status)
rh_status
;;
condrestart|try-restart)
rh_status_q || exit 0
;;
*)
echo $"Usage: $0 {start|stop|status|restart|condrestart|try-restart|reload|force-
reload|configtest}"
exit 2
esac
为脚本赋予执行权限
[[email protected] ~]# chmod +x /etc/rc.d/init.d/nginx
添加至服务管理列表，并让其开机自动启动
[[email protected] ~]# chkconfig --add nginx [[email protected] ~]# chkconfig nginx on
配置nginx
[[email protected] ~]# vim /etc/nginx/nginx.conf
upstream www.scholar.com {
server 172.16.10.123:8080;
server 172.16.10.124:8080;
}
server {
listen 80;
server_name www.scholar.com;
location / {
proxy_pass http://www.scholar.com;
index index.jsp index.html index.htm;
}
}
[[email protected] ~]# service nginx start
Starting nginx: [ OK ]
tomcat安装配置
安装jdk
[[email protected] ~]# rpm -ivh jdk-7u79-linux-x64.rpm [[email protected] ~]# vim /etc/profile.d/java.sh export JAVA_HOME=/usr/java/latest export PATH=$JAVA_HOME/bin:$PATH [[email protected] ~]# . /etc/profile.d/java.sh
安装tomcat
[[email protected] ~]# tar xf apache-tomcat-7.0.62.tar.gz -C /usr/local/ [[email protected] ~]# cd /usr/local/ [[email protected] local]# ln -sv apache-tomcat-7.0.62/ tomcat [[email protected] local]# vim /etc/profile.d/tomcat.sh export CATALINA_HOME=/usr/local/tomcat export PATH=$CATALINA_HOME/bin:$PATH [[email protected] local]# . /etc/profile.d/tomcat.sh
提供脚本
[[email protected] local]# vim /etc/rc.d/init.d/tomcat
#!/bin/sh
# Tomcat init script for Linux.
#
# chkconfig: 2345 96 14
# description: The Apache Tomcat servlet/JSP container.
# JAVA_OPTS=‘-Xms64m -Xmx128m‘
JAVA_HOME=/usr/java/latest
CATALINA_HOME=/usr/local/tomcat
export JAVA_HOME CATALINA_HOME
case $1 in
start)
exec $CATALINA_HOME/bin/catalina.sh start ;;
stop)
exec $CATALINA_HOME/bin/catalina.sh stop;;
restart)
$CATALINA_HOME/bin/catalina.sh stop
sleep 2
exec $CATALINA_HOME/bin/catalina.sh start ;;
*)
echo "Usage: `basename $0` {start|stop|restart}"
exit 1
;;
esac
[[email protected] local]# chmod +x /etc/rc.d/init.d/tomcat
[[email protected] local]# chkconfig --add tomcat
[[email protected] local]# chkconfig tomcat on
#两个tomcat节点都执行以上操作
访问测试
准备测试页
[[email protected] local]# cd tomcat/webapps/
[[email protected] webapps]# mkdir -pv test/WEB-INF/{classes,lib}
[[email protected] webapps]# cd test/
[[email protected] test]# vim index.jsp
<%@ page language="java" %>
<html>
<head><title>TomcatA</title></head>
<body>
<h1><font color="red">TomcatA.scholar.com</font></h1>
<table align="centre" border="1">
<tr>
<td>Session ID</td>
<% session.setAttribute("scholar.com","scholar.com"); %>
<td><%= session.getId() %></td>
</tr>
<tr>
<td>Created on</td>
<td><%= session.getCreationTime() %></td>
</tr>
</table>
</body>
</html>
#另一个节点将TomcatA替换为TomcatB，颜色设为蓝色
[[email protected] test]# service tomcat start
此时Session信息并不一致，接下来我们通过配置MSM实现Session共享
memcached安装
#解决依赖关系 [[email protected] ~]# yum groupinstall "Development Tools" "Server Platform Deveopment" -y #安装libevent #memcached依赖于libevent API，因此要事先安装之 [[email protected] ~]# tar xf libevent-2.0.22-stable.tar.gz [[email protected] ~]# cd libevent-2.0.22-stable [[email protected] libevent-2.0.22-stable]# ./configure --prefix=/usr/local/libevent [[email protected] libevent-2.0.22-stable]# make && make install [[email protected]lar ~]# echo "/usr/local/libevent/lib" > /etc/ld.so.conf.d/libevent.conf [[email protected] ~]# ldconfig #安装配置memcached [[email protected] ~]# tar xf memcached-1.4.24.tar.tar [[email protected] ~]# cd memcached-1.4.24 [[email protected] memcached-1.4.24]# ./configure --prefix=/usr/local/memcached --with-libevent=/usr/local/libevent [[email protected] memcached-1.4.24]# make && make install
提供脚本
[[email protected] ~]# vim /etc/init.d/memcached
#!/bin/bash
#
# Init file for memcached
#
# chkconfig: - 86 14
# description: Distributed memory caching daemon
#
# processname: memcached
# config: /etc/sysconfig/memcached
. /etc/rc.d/init.d/functions
## Default variables
PORT="11211"
USER="nobody"
MAXCONN="1024"
CACHESIZE="64"
RETVAL=0
prog="/usr/local/memcached/bin/memcached"
desc="Distributed memory caching"
lockfile="/var/lock/subsys/memcached"
start() {
echo -n $"Starting $desc (memcached): "
daemon $prog -d -p $PORT -u $USER -c $MAXCONN -m $CACHESIZE
RETVAL=$?
[ $RETVAL -eq 0 ] && success && touch $lockfile || failure
echo
return $RETVAL
}
stop() {
echo -n $"Shutting down $desc (memcached): "
killproc $prog
RETVAL=$?
[ $RETVAL -eq 0 ] && success && rm -f $lockfile || failure
echo
return $RETVAL
}
restart() {
stop
start
}
reload() {
echo -n $"Reloading $desc ($prog): "
killproc $prog -HUP
RETVAL=$?
[ $RETVAL -eq 0 ] && success || failure
echo
return $RETVAL
}
case "$1" in
start)
start
;;
stop)
stop
;;
restart)
restart
;;
condrestart)
[ -e $lockfile ] && restart
RETVAL=$?
;;
reload)
reload
;;
status)
status $prog
RETVAL=$?
;;
*)
echo $"Usage: $0 {start|stop|restart|condrestart|status}"
RETVAL=1
esac
exit $RETVAL
授权并启动服务
[[email protected] ~]# chmod +x /etc/init.d/memcached [[email protected] ~]# chkconfig --add memcached [[email protected] ~]# chkconfig memcached on [[email protected] ~]# service memcached start #两个memcached节点都执行以上操作
tomcat配置
将所需jar包放入各tomcat节点的tomcat安装目录下的lib目录中
[[email protected] ~]# cd msm/ [[email protected] msm]# ls javolution-5.4.3.1.jar msm-javolution-serializer-1.8.1.jar memcached-session-manager-1.8.1.jar spymemcached-2.10.2.jar memcached-session-manager-tc7-1.8.1.jar [[email protected] msm]# cp * /usr/local/tomcat/lib/ #各tomcat节点都需执行以上操作
[[email protected] msm]# vim /usr/local/tomcat/conf/server.xml <?xml version=‘1.0‘ encoding=‘utf-8‘?> <Server port="8005" shutdown="SHUTDOWN"> <Listener className="org.apache.catalina.startup.VersionLoggerListener" /> <Listener className="org.apache.catalina.core.AprLifecycleListener" SSLEngine="on" /> <Listener className="org.apache.catalina.core.JasperListener" /> <Listener className="org.apache.catalina.core.JreMemoryLeakPreventionListener" /> <Listener className="org.apache.catalina.mbeans.GlobalResourcesLifecycleListener" /> <Listener className="org.apache.catalina.core.ThreadLocalLeakPreventionListener" /> <GlobalNamingResources> <Resource name="UserDatabase" auth="Container" type="org.apache.catalina.UserDatabase" description="User database that can be updated and saved" </GlobalNamingResources> <Service name="Catalina"> <Connector port="8080" protocol="HTTP/1.1" connectionTimeout="20000" redirectPort="8443" /> <Connector port="8009" protocol="AJP/1.3" redirectPort="8443" /> <Engine name="Catalina" defaultHost="localhost"> <Realm className="org.apache.catalina.realm.LockOutRealm"> <Realm className="org.apache.catalina.realm.UserDatabaseRealm" resourceName="UserDatabase"/> </Realm> <Host name="www.scholar.com" appBase="webapps" unpackWARs="true" autoDeploy="true"> <Context path="/test" docBase="/usr/local/tomcat/webapps/test/" reloadable="true"> <Manager className="de.javakaffee.web.msm.MemcachedBackupSessionManager" memcachedNodes="n1:172.16.10.126:11211,n2:172.16.10.212:11211" failoverNodes="n1" requestUriIgnorePattern=".*\.(ico|png|gif|jpg|css|js)$" transcoderFactoryClass="de.javakaffee.web.msm.serializer.javolution.Javolu tionTranscoderFactory" /> </Context> <Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs" prefix="scholar_access_log." suffix=".txt" pattern="%h %l %u %t "%r" %s %b" /> </Host> <Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs" prefix="scholar_access_log." suffix=".txt" pattern="%h %l %u %t "%r" %s %b" /> </Host> <Host name="localhost" appBase="webapps" unpackWARs="true" autoDeploy="true"> <Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs" prefix="localhost_access_log." suffix=".txt" pattern="%h %l %u %t "%r" %s %b" /> </Host> </Engine> </Service> </Server>
将配置文件同步至另一节点
[[email protected] msm]# scp /usr/local/tomcat/conf/server.xml node2:/usr/local/tomcat/conf/ [[email protected] msm]# service tomcat restart ssh node2 ‘service tomcat restart‘
访问测试
由此可见，Session共享已实现，下面我们模拟TomcatB节点故障，看一下Session是否会发生改变
[[email protected] msm]# service tomcat stop
虽然因为TomcatB故障，导致用户请求被调度到了TomcatA节点上，但Session ID并未发生改变，即Session集群内的所有节点都保存有全局的Session信息，很好的实现了用户访问的不中断
当n2（memcached）节点发生故障，Session信息会不会转移到其他memcached节点呢，我们来试一下
[[email protected] ~]# service memcached stop
Session已转移到n1上，而且Session ID并未发生改变，至此，Tomcat基于MSM+Memcached实现Session共享目的已实现
The end
Tomcat基于MSM+Memcached实现Session共享实验就说到这里了，实验过程中遇到问题可留言交流。以上仅为个人学习整理，如有错漏，大神勿喷~~~
时间： 2024-10-14 03:56:08