Terracotta and Tomcat Clustering - Page 一

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 :)

1. How to install Terracotta in an Active/Passive HA (High Availability) model.
2. How to configure Tomcat 6.0 to store/retrieve sessions on Terracotta.
3. 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:

1. Clients' sessions data are part of the Tomcat JVM instance.
2. There is extra work for Tomcat to make sure that the sessions and its data are replicated among the cluster
3. not suitable for larger cluster because of using?multicasting, imagine the network traffic generated by eight tomcat nodes replicating their sessions.
4. 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?

?

?

it is really simple:

?

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

Let's Digg in

First things first! we need:

1. terracotta-3.7.0-installer.jar
2. apache-tomcat-6.0.35
3. mod_jk.so
4. httpd-2.2.22
5. 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>

1. for each Terracotta server that will run in the cluster you need to define a server node.
2. 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

we have now defined two servers, we need to?define how they would work.