tomcat使用指南（四）-简单集群

对于使用tomcat搭建的web应用，很少只部署一个tomcat。只部署一个tomcat有几个缺点：
1、万一这个tomcat挂掉了，整个应用就访问不了
2、当需要重启tomcat时，重启期间应用访问不了
3、当访问量瞬时增大时，单个web server会负载不了
集群可以解决这三个问题。集群、负载均衡、session共享、分布式都是不同的概念。

这些概念在《Tomcat权威指南（第二版）》的集群那一章节有详细介绍。这里不叙述。

简单的集群只需要三步，非常简单：

1、配置tomcat集群

2、安装apache httpd

3、配置httpd

不过有一点需要注意，httpd可以集群，但处理静态页面很慢，我试过直接访问tomcat1很快，但通过httpd访问非常慢。下一篇文章会讨论这个问题的优化。

环境版本：

windows xp+tomcat7.0.57+tomcat7.0.57+httpd2.4.4 测试通过

（aix6.1+tomcat7.0.57+tomcat7.0.57）+（aix6.1+httpd2.4.2） 测试通过

apache http server查看版本方法：

[drecv1@test1:/usr/local/apache/bin]$httpd -VServer version: Apache/2.4.2 (Unix)Server built:   Jul 18 2012 11:10:49Server's Module Magic Number: 20120211:3Server loaded:  APR 1.4.6, APR-UTIL 1.4.1Compiled using: APR 1.4.6, APR-UTIL 1.4.1

配置tomcat集群

1、改端口
见  tomcat使用指南（二）-修改端口
2、增加jvmRoute="jvm1"

假设是两台tomcat，修改server.xml，分别增加为1和2：
<Engine name="Catalina" defaultHost="localhost" jvmRoute="jvm1">
<Engine name="Catalina" defaultHost="localhost" jvmRoute="jvm2">

3、修改server.xml，在host节点后，增加cluster节点：

注意，port="5000"要每台不一样。

<Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster"                 channelSendOptions="6">           <Manager className="org.apache.catalina.ha.session.BackupManager"                   expireSessionsOnShutdown="false"                   notifyListenersOnReplication="true"                   mapSendOptions="6"/>          <!--          <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="5000"                      selectorTimeout="100"                      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"/>            <Interceptor className="org.apache.catalina.tribes.group.interceptors.ThroughputInterceptor"/>          </Channel>           <Valve className="org.apache.catalina.ha.tcp.ReplicationValve"                 filter=".*\.gif|.*\.js|.*\.jpeg|.*\.jpg|.*\.png|.*\.htm|.*\.html|.*\.css|.*\.txt"/>           <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>

安装httpd

注意：linux需要安装apr和apr-util，windows是不需要，直接解压zip即可。

http://apr.apache.org/download.cgi

下载apr-1.5.1.tar.gz和apr-util-1.5.4.tar.gz


http://httpd.apache.org/download.cgi#apache24
下载httpd-2.4.12.tar.gz，解压


把两个apr移动到httpd-2.4.12/srclib下，解压


[builder@crmint-tp02 ~/tomcat/httpd-2.4.12/srclib]$gzip -d apr-1.5.1.tar.gz
[builder@crmint-tp02 ~/tomcat/httpd-2.4.12/srclib]$gzip -d apr-util-1.5.4.tar.gz
[builder@crmint-tp02 ~/tomcat/httpd-2.4.12/srclib]$tar xvf apr-1.5.1.tar
[builder@crmint-tp02 ~/tomcat/httpd-2.4.12/srclib]$tar xvf apr-util-1.5.4.tar


根据官方文档：
http://httpd.apache.org/docs/2.4/install.html
需要把版本去掉：
[builder@crmint-tp02 ~/tomcat/httpd-2.4.12/srclib]$mv apr-1.5.1 apr
[builder@crmint-tp02 ~/tomcat/httpd-2.4.12/srclib]$mv apr-util-1.5.4 apr-util


apr安装
# cd srclib/apr
# ./configure --prefix=/usr/local/apr
# make
# make install


apr、apr-util、httpd安装
./configure --prefix=/usr/local/apr
./configure usr/local/apr-util -enable-lib64 --with-apr=/usr/local/apr --with-expat=builtin
./configure --prefix=/usr/local/apache2 --enable-so --enable-rewrite


安装后
[drecv1@bss_test1:/usr/local]$ls
apache    apr       apr-util  bin       pcre      tar_bak


启动
cd /usr/local/apache2/bin/
./apachectl start


停止
./apachectl stop


apache重新启动命令：
/usr/local/apache2/bin/apachectl restart


附：
没有安装apr的报错：
[builder@crmint-tp02 ~/tomcat/httpd-2.4.12]$./configure --prefix=/usr/local/apache2 --enable-so --enable-rewrite
checking for chosen layout... Apache
checking for working mkdir -p... yes
checking for grep that handles long lines and -e... /bin/grep
checking for egrep... /bin/grep -E
checking build system type... x86_64-unknown-linux-gnu
checking host system type... x86_64-unknown-linux-gnu
checking target system type... x86_64-unknown-linux-gnu
configure: 
configure: Configuring Apache Portable Runtime library...
configure: 
checking for APR... no
configure: error: APR not found.  Please read the documentation.
[builder@crmint-tp02 ~/tomcat/httpd-2.4.12]$

配置httpd

cd /usr/local/apache/conf
vi httpd.conf


#把以下8个放开注释
LoadModule lbmethod_byrequests_module modules/mod_lbmethod_byrequests.so
LoadModule proxy_module modules/mod_proxy.so
LoadModule proxy_ajp_module modules/mod_proxy_ajp.so
LoadModule proxy_balancer_module modules/mod_proxy_balancer.so
LoadModule proxy_connect_module modules/mod_proxy_connect.so
LoadModule proxy_ftp_module modules/mod_proxy_ftp.so
LoadModule proxy_http_module modules/mod_proxy_http.so
LoadModule slotmem_shm_module modules/mod_slotmem_shm.so


在最后（也就是#</IfModule>下面）增加：
ProxyPass / balancer://cluster/ stickysession=JSESSIONID
 
ProxyPassReverse / balancer://cluster/
<proxy balancer://cluster>
          BalancerMember ajp://130.51.9.105:8009 loadfactor=1 route=jvm1
          BalancerMember ajp://130.51.9.105:8010 loadfactor=1 route=jvm2
</proxy>

附录：
部分so不放开注释的报错提示与其他报错的解决方法：
[Tue Feb 03 19:58:24.046875 2015] [proxy_balancer:emerg] [pid 4644:tid 1724] AH01177: Failed to lookup provider 'shm' for 'slotmem': is mod_slotmem_shm loaded??
需放开mod_slotmem_shm注释


[Tue Feb 03 19:59:57.437500 2015] [proxy:crit] [pid 6896:tid 1716] AH02432: Cannot find LB Method: byrequests
[Tue Feb 03 19:59:57.437500 2015] [proxy_balancer:emerg] [pid 6896:tid 1716] (22)Invalid argument: AH01183: Cannot share balancer
需放开lbmethod_byrequests_module


[Tue Feb 03 19:55:35.640625 2015] [core:warn] [pid 5980:tid 1736] AH00098: pid file F:/Apache24/logs/httpd.pid overwritten -- Unclean shutdown of previous Apache run?
删掉pid文件可解决


F:\Apache24\bin>httpd.exe
AH00558: httpd.exe: Could not reliably determine the server's fully qualified domain name, using 130.51.23.43. Set the 'ServerName' directive globally to suppress this message
#ServerName www.example.com:80改名ServerName 30.51.23.43


F:\Apache24\bin>httpd.exe
httpd.exe: Syntax error on line 37 of F:/Apache24/conf/httpd.conf: ServerRoot must be a valid directory
解决：如果你不是解压在c:/Apache24这个默认目录，则需要修改ServerRoot "f:/Apache24"等4处地方

本文出处：

http://blog.csdn.net/ouyida3

2015.2.6