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以一个apache2.2前端，2个tomcat6后端为例，tomcat服务器在内网，apache服务器具有内网和外网接口。本文使用JK模块实现负载均衡。
一、建立tomcat负载均衡

1.修改tomcat的conf目录下的server.xml文件，

去掉对jvmRoute这一行的注释，并且把jvmRoute的值改为例如tomcat1这样容易记忆的字符。



   1. <Engine name="Catalina" defaultHost="localhost" jvmRoute="tomcat1">  

<Engine name="Catalina" defaultHost="localhost" jvmRoute="tomcat1">

把2个tomcat服务器上的上述文件都作修改。

2.在apache的conf目录下建立workers.properties文件，内容如下



   1. # The advanced router LB worker  
   2. worker.list=router  
   3. # Define a worker using ajp13  
   4. worker.worker1.port=8009  
   5. worker.worker1.host=192.168.56.3  
   6. worker.worker1.type=ajp13  
   7. worker.worker1.lbfactor=1  
   8. # Define preferred failover node for worker1  
   9. worker.worker1.redirect=worker2  
  10. worker.worker1.route=tomcat1  
  11. # Define another worker using ajp13  
  12. worker.worker2.port=8009  
  13. worker.worker2.host=192.168.56.4  
  14. worker.worker2.type=ajp13  
  15. worker.worker2.lbfactor=1  
  16. # Disable worker2 for all requests except failover  
  17. #worker.worker2.activation=disabled  
  18. worker.worker2.route=tomcat2  
  19.    
  20. # Define the LB worker  
  21. worker.router.type=lb  
  22. worker.router.balance_workers=worker1,worker2  
  23. #worker.router.sticky_session_force=1  
  24. # Add the status worker to the worker list  
  25. worker.list=jkstatus  
  26. # Define a 'jkstatus' worker using status  
  27. worker.jkstatus.type=status  

# The advanced router LB worker worker.list=router # Define a worker using ajp13 worker.worker1.port=8009 worker.worker1.host=192.168.56.3 worker.worker1.type=ajp13 worker.worker1.lbfactor=1 # Define preferred failover node for worker1 worker.worker1.redirect=worker2 worker.worker1.route=tomcat1 # Define another worker using ajp13 worker.worker2.port=8009 worker.worker2.host=192.168.56.4 worker.worker2.type=ajp13 worker.worker2.lbfactor=1 # Disable worker2 for all requests except failover #worker.worker2.activation=disabled worker.worker2.route=tomcat2 # Define the LB worker worker.router.type=lb worker.router.balance_workers=worker1,worker2 #worker.router.sticky_session_force=1 # Add the status worker to the worker list worker.list=jkstatus # Define a 'jkstatus' worker using status worker.jkstatus.type=status

其中的



   1. worker.worker1.route=tomcat1  

worker.worker1.route=tomcat1  

中的tomcat1对应第1个tomcat服务器中上述server.xml中的jvmRoute的内容。

同样的，



   1. worker.worker2.route=tomcat2  

worker.worker2.route=tomcat2  

中的tomcat2对应第2个tomcat服务器中上述server.xml中的jvmRoute的内容。

3.在apache的conf目录下的httpd.conf文件末尾添加如下内容



   1. # Load mod_jk module  
   2. # Update this path to match your modules location  
   3. LoadModule    jk_module  modules/mod_jk.so  
   4. # Declare the module for <IfModule directive> (remove this line on Apache 2.x)  
   5. #AddModule     mod_jk.c  
   6. # Where to find workers.properties  
   7. # Update this path to match your conf directory location (put workers.properties next to httpd.conf)  
   8. JkWorkersFile conf/workers.properties  
   9. # Where to put jk shared memory  

# Load mod_jk module # Update this path to match your modules location LoadModule jk_module modules/mod_jk.so # Declare the module for <IfModule directive> (remove this line on Apache 2.x) #AddModule mod_jk.c # Where to find workers.properties # Update this path to match your conf directory location (put workers.properties next to httpd.conf) JkWorkersFile conf/workers.properties # Where to put jk shared memory

4.为了能够在运行时查看jk的状态，在上述内容末尾再添加如下内容



   1.  # Update this path to match your local state directory or logs directory  
   2.  JkShmFile     logs/mod_jk.shm  
   3.  # Where to put jk logs  
   4.  # Update this path to match your logs directory location (put mod_jk.log next to access_log)  
   5.  JkLogFile     logs/mod_jk.log  
   6.  # Set the jk log level [debug/error/info]  
   7.  JkLogLevel    info  
   8.  # Select the timestamp log format  
   9.  JkLogStampFormat "[%a %b %d %H:%M:%S %Y] "  
  10.  # Send everything for context /examples to worker named worker1 (ajp13)  
  11.  JkMount  /examples/* router  
  12.  # Add the jkstatus mount point  
  13.  JkMount /jkmanager/* jkstatus  
  14.    # Enable the JK manager access from localhost only  
  15. <Location /jkmanager/>  
  16.    JkMount jkstatus  
  17.    Order deny,allow  
  18.    Deny from all  
  19.    Allow from 127.0.0.1  
  20. </Location>  

# Update this path to match your local state directory or logs directory JkShmFile logs/mod_jk.shm # Where to put jk logs # Update this path to match your logs directory location (put mod_jk.log next to access_log) JkLogFile logs/mod_jk.log # Set the jk log level [debug/error/info] JkLogLevel info # Select the timestamp log format JkLogStampFormat "[%a %b %d %H:%M:%S %Y] " # Send everything for context /examples to worker named worker1 (ajp13) JkMount /examples/* router # Add the jkstatus mount point JkMount /jkmanager/* jkstatus # Enable the JK manager access from localhost only <Location /jkmanager/> JkMount jkstatus Order deny,allow Deny from all Allow from 127.0.0.1 </Location>

5.需要注意的是，JK模块的默认配置是支持session黏性的，即用户的session在其生命周期内始终保存在一个tomcat服务器上。

关于如何设置为非sessin黏性等，请参考tomcat官方文档：LoadBalancer HowTo http://tomcat.apache.org/connectors-doc/generic_howto/loadbalancers.html
二、配置session复制

1.修改tomcat的conf目录下的server.xml文件，

去掉对这一行的注释，即可使tomcat服务支持session复制。



   1. <Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster"/>  

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

2.修改希望复制session的应用的WEB-INF目录下的web.xml文件，

在末尾增加一行



   1. <distributable/>   

<distributable/> 

以使该应用支持session复制。

把2个tomcat服务器上的希望实现session复制的应用中的上述文件都作修改。

3.分别先后启动2个tomcat服务，你会发现启动信息中增加了一些session复制的信息。当第1个tomcat启动完毕，在启动第2个tomcat服务时，log里面会记录寻找可作session复制的第1个tomcat的信息。即寻找簇内服务器的过程。

当停止任何一个tomcat服务后，也会在正在运行的tomcat服务的log中看到有那个tomcat服务停止了的消息。

4.如果想实现更复杂的sessioin复制功能，可以参考tomcat官方文档：

Clustering/Session Replication HOW-TO http://tomcat.apache.org/tomcat-6.0-doc/cluster-howto.html

2012年3月10日 10:36

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