Performance Tuning for Content Manager

Chapter 2. Content Manager base products 63

Virtual host

A virtual host is a configuration that enables a single host machine to resemble

multiple host machines. Resources that are associated with one virtual host

cannot share data with resources associated with another virtual host, even if the

virtual hosts share the same physical machine.

Each virtual host has a logical name and a list of one or more DNS aliases by

which it is known. A DNS alias is the TCP/IP host name and port number that is

used to request the servlet (for example, yourHostName:80). The default ports

and aliases are:

 The default alias is *:80, using an external HTTP port that is not secure.

 Aliases of the form *:9080 use the embedded HTTP port that is not secure.

 Aliases of the form *:443 use the secure external HTTPS port.

 Aliases of the form *:9443 use the secure embedded HTTPS port.

When a servlet request is made, the server name and port number entered into

the browser are compared to a list of all known aliases in an effort to locate the

correct virtual host and serve the servlet. If no match is found, an error (404) is

returned to the browser.

WebSphere Application Server provides a default virtual host, aptly named

“default_host,” with some common aliases, such as the machine’s IP address,

short host name, and fully qualified host name. The alias comprises the first part

of the path for accessing a resource such as a servlet. For example, it is

“localhost:80” in the request http://localhost:80/servlet/snoop.

Virtual hosts enable the administrator to isolate, and independently manage,

multiple sets of resources on the same physical machine.

2.2.4 Performance-related tools and concepts

WebSphere Application Server provides a set of features and tools that are

closely related to the performance of the system. In this section, we give an

overview of the performance-related concepts:

 Performance Monitoring Infrastructure

 Performance Advisors

 Dynamic caching

 Java Virtual Machine Profiler Interface

 Parameter hot list

64 Performance Tuning for Content Manager

Performance Monitoring Infrastructure

For the WebSphere environment, we provide the Performance Monitoring

Infrastructure (PMI) to capture performance data with minimal performance

impact to incorporate that data into an overall monitoring solution.

PMI uses a client-server architecture. The server collects performance data in

memory within the WebSphere Application Server. This data consists of counters

such as servlet response time and data connection pool usage. A client can then

retrieve that data using a Web client, a Java client, or a Java Management

Extension (JMX™) client. A client is an application that retrieves performance

data from one or more servers and processes the data. Clients can include:

 Graphical user interfaces (GUIs) that display performance data in real time

 Applications that monitor performance data and trigger different events

according to the current values of the data

 Any other application that needs to receive and process performance data

The PMI components and infrastructure have been extended and updated in

WebSphere Application Server V5.1 to support the new management structure

and to comply with the Performance Data Framework of the J2EE Management

Specification. WebSphere Application Server contains

Tivoli Performance

Viewer

, a Java client that displays and monitors performance data.

PMI is composed of components for collecting performance data on the

application server side and components for communicating between runtime

components and between the clients and servers.

Figure 2-10 on page 65 shows the overall PMI architecture. On the right side, the

server updates and keeps PMI data in memory. The left side displays a Web

client, Java client, and JMX client retrieving the performance data.