HP Enterprise Cluster Master Toolkit User Guide (5900-2131, December 2011)

Tomcat Package Configuration Overview
Tomcat starts up by reading the server.xml file from the conf sub-directory of the
CATALINA_BASE directory which is configured in the toolkit user configuration file
hatomcat.conf.
The configuration rules include the following:
• Each node must have the same version of the HP-UX based Tomcat Servlet Engine.
• Each node must have the same CATALINA_BASE directory where identical copies of the
configuration file for each instance are placed.
• Each node must have the same document root directory where identical copies of the web
document for each instance are placed.
Tomcat servlet engine can be configured in two different ways:
• Local Config: Putting the configuration and other web-site files on a single node, and then
replicating the files to all other nodes in the cluster
• Shared config: with configuration files and document root files in a shared file system
NOTE: Under a shared configuration, you can choose to put tomcat binaries as well in a shared
file system. The steps to configure this is covered in this document later.
Local Configuration
In a typical local configuration, nothing is shared between the nodes. Identical copies of the Tomcat
server configuration file and web documents reside in exactly the same locations on each node.
The user is responsible for maintaining identical copies of the tomcat components on the different
nodes. This is useful when the information on the web-page is static.
If the user chooses to use this configuration, it is the user's responsibility to ensure the data is
propagated to all nodes, and is consistently maintained. A disadvantage of storing the configuration
on local disks is that this can increase the chance of the configuration for a Tomcat instance
becoming inconsistent if changes are made, but not distributed to all nodes that can run that Tomcat
instance.
Shared Configuration
In a typical shared configuration, the web application directories are all on the shared file system.
(Placing the CATALINA_BASE directory in the shared file system is optional.) Since the web
applications (along with the tomcat configuration directory) are on shared storage - accessible to
all nodes in the cluster - there is no need to maintain local identical copies of the files on each
node. The mount point of the shared file system should be identical across all the tomcat package
nodes. Hence this is the recommended Tomcat package configuration.
Each web site is assigned IP addresses (or domain addresses that maps to particular IP addresses)
through the configuration file. These relocatable IP addresses are created for each Tomcat package.
They are added to the Package Control Script in case of legacy packages or the Package ASCII
file in case of modular packages. When the Tomcat package is switched over from one node to
another, this particular instance is stopped and IP addresses are removed on the primary node,
then the IP addresses are reallocated and the instance is started on the adoptive node. Clients will
then be automatically connected through these IP addresses to the web site on the adoptive node.
Multiple Tomcat Instances Configuration
Tomcat servlet engine is a multi-instance application. More than one instance of the Tomcat can
run on a single node simultaneously. For example, if two nodes are each running an instance of
Tomcat and one node fails, the Tomcat instance on the failed node can be successfully failed over
to the healthy node. In addition, the healthy node can continue to run its own instance as well.
Multiple Tomcat instance configuration can either be done as a local configuration or shared
112 Using Tomcat Toolkit in a HP Serviceguard Cluster