Terracotta and Tomcat Clustering

killerxf

原网址：http://javadrama.blogspot.com/2012/10/terracotta-and-tomcat-clustering-page-1.html


In this tutorial we will learn a lot of stuff :)

• How to install Terracotta in an Active/Passive HA (High Availability) model.
  
• How to configure Tomcat 6.0 to store/retrieve sessions on Terracotta.
  
• How to install and configure Apache Web Server configure it to relay requests to Tomcat.
  

Why?

i can do session replication using Tomcat built-in clustering module, so why do i use Terracotta?

well, the Tomcat clustering works just perfect with major four concerns:

• Clients' sessions data are part of the Tomcat JVM instance.
  
• There is extra work for Tomcat to make sure that the sessions and its data are replicated among the cluster
  
• not suitable for larger cluster because of using multicasting, imagine the network traffic generated by eight tomcat nodes replicating their sessions.
  
• You can't store an object which is not serializable.
  

So, moving this responsibility to Terracotta would help eliminating those four concerns.




Our Final architecture 

http://five.rdaili.com/sohu.com.php?u=2hpDLHla4MzrNVZwR47dqRDhGv36V5Wmh8Je5EqHiNewe0zfjvQHxz8zsk4OabRbRzsKY852vv%2FyEL2aT5PakC0pyawKurGvi2YHIObjHtMlsrs%2FZhkEJV4%3D&b=3

 

 

it is really simple:

 

• Both Tomcats store/retrieve sessions on the active Terracotta server.
  
• Apache web server forwards requests to both Tomcats.
  
• If the active Terracotta fails the passive Terracotta will be the active.
  

Let's Digg in

First things first! we need:

• terracotta-3.7.0-installer.jar
  
• apache-tomcat-6.0.35
  
• mod_jk.so
  
• httpd-2.2.22
  
• JDK 1.6
  

My five servers built on a single windows 7 box as a POC, you should have no troubles with running the same example on Linux, only minor chages are needed.

Install and Configure Terracotta

open a terminal and change the directory to the place where you downloaded terracotta-3.7.0-installer.jar

java -jar terracotta-3.7.0-installer.jar



you will see a setup wizard, it is straight forward, install Terracotta to the directory of your choice, from now on i will refer to that directory as ${TC_HOME}
now, go to ${TC_HOME} and create a new directory called 'config', this directory will contain our Terracotta configuration file that will set up the Terracotta cluster.
create a new file inside the config directory called tc-config.xml with the following content:



<tc-config xmlns="/config">
<servers secure="false" xmlns:tc="/config" xmlns:con="/config" xmlns="">
<server bind="0.0.0.0" host="127.0.0.1" name="node1">
<data>C:\terracotta\server-data</data>
<logs>C:\terracotta\server-logs</logs>
<statistics>C:\terracotta\server-statistics</statistics>
<dso-port bind="0.0.0.0">9510</dso-port>
<jmx-port bind="0.0.0.0">9520</jmx-port>
<l2-group-port bind="0.0.0.0">9530</l2-group-port>
<data-backup>C:\terracotta\data-backup</data-backup>
<index>C:\terracotta\server-data\index</index>
<dso>
<client-reconnect-window>120</client-reconnect-window>
<persistence>
<mode>temporary-swap-only</mode>
</persistence>
<garbage-collection>
<enabled>true</enabled>
<verbose>false</verbose>
<interval>3600</interval>
</garbage-collection>
</dso>
</server>
<server bind="0.0.0.0" host="127.0.0.1" name="node2">
<data>C:\terracotta\server-data2</data>
<logs>C:\terracotta\server-logs2</logs>
<statistics>C:\terracotta\server-statistics2</statistics>
<dso-port bind="0.0.0.0">9511</dso-port>
<jmx-port bind="0.0.0.0">9521</jmx-port>
<l2-group-port bind="0.0.0.0">9531</l2-group-port>
<data-backup>C:\terracotta\data-backup2</data-backup>
<index>C:\terracotta\server-data\index2</index>
<dso>
<client-reconnect-window>120</client-reconnect-window>
<persistence>
<mode>temporary-swap-only</mode>
</persistence>
<garbage-collection>
<enabled>true</enabled>
<verbose>false</verbose>
<interval>3600</interval>
</garbage-collection>
</dso>
</server>
<mirror-groups>
<mirror-group>
<members>
<member>node1</member>
<member>node2</member>
</members>
</mirror-group>
</mirror-groups>
<ha>
<mode>networked-active-passive</mode>
<networked-active-passive>
<election-time>5</election-time>
</networked-active-passive>
</ha>
<update-check>
<enabled>true</enabled>
<period-days>7</period-days>
</update-check>
</servers>
<system xmlns:tc="/config" xmlns:con="/config" xmlns="">
<configuration-model>production</configuration-model>
</system>
<clients xmlns:tc="/config" xmlns:con="/config" xmlns="">
<logs>%(user.home)/terracotta/client-logs</logs>
<modules>
<module name="terracotta-toolkit-1.6" group-id="org.terracotta.toolkit"/>
</modules>
</clients>
</tc-config>
the important thing to note here is the servers node

 

• for each Terracotta server that will run in the cluster you need to define a server node.
  
• the server tag has three attributes:
  

• bind: the default bind address which Terracotta listen to.
  
• host: the IP address that will be used to connect to the Terracotta server.
  
• name: the name of this node
  

data: is where this server stores its data (make it unique for each server if you are running the cluster on one box)
logs: is where the server store its logs (make it unique for each server if you are running the cluster on one box)
statistics:  is where the server store its statistics (make it unique for each server if you are running the cluster on one box)
port configurations: JMX, DSO and group ports (make it unique for each server if you are running the cluster on one box)
data-backup: is where the server store its data backups  (make it unique for each server if you are running the cluster on one box)
index: is where the server store its index files  (make it unique for each server if you are running the cluster on one box)
dso: is the Distributed Shared Objects specific options.　　we have now defined two servers, we need to define how they would work.

• mirror-group: a tag to define Terracotta groups 
  

• members: a tag to add a server to a group using its name
  

ha: is a tag to define the High Availability options of the group

• mode: networked-active-passive it means that the communications between the servers will relay on networking.
  
• election-time: the Terracotta server would wait for that time to decide if it should start as an Active or passive.
  

let's start out cluster an make sure everything is OK.
 

• open three consoles and navigate to ${TC_HOME}\bin on the three of them
  
• Start node1
  start-tc-server.bat -f ..\config\tc-config.xml -n node1
  
  you should see
  Becoming State[ ACTIVE-COORDINATOR ]
  Terracotta Server instance has started up as ACTIVE node on 0.0.0.0:9510 successfully, and is now ready for work.
  
• Start node2
  start-tc-server.bat -f ..\config\tc-config.xml -n node2
  
  you should see
  NodeID[127.0.0.1:9510] joined the cluster
  Moved to State[ PASSIVE-UNINITIALIZED ]
  Moved to State[ PASSIVE-STANDBY ]
  
• on the third console start the Terracotta Development Console
  dev-console.bat
  
  connect to either 127.0.0.1:9520 or 127.0.0.1:9521, you should see this screen
  

http://five.rdaili.com/sohu.com.php?u=2hpDKXla4MzrNVZwR47dqRDhGv36V6DHsfwC0BuDutzBe0zfjs1G7mwIkx4OabRbRzsKY852vv%2FiELbWVaDT6zx377AaurGvi2YHAObjDZwsrag%3D&b=3

 

as per the screen shot, node1 is active and node2 is passive, play around by taking node1 down and see if node2 becomes the active and then Vice Versa.