Each request
from the Web browser contains the name of a service that fulfills
the request. The Application Broker identifies the service by looking
into its configuration file and then determines where and how the
request should be forwarded. The configuration file defines the three
services (socket, launch, and pool) that are available for Application
Dispatcher applications to use.
A socket
service runs the Application Server continuously, waiting for new
requests, and refers to the protocol that is used (TCP/IP sockets)
to communicate between the server and the Application Broker. Using
this type of service, many servers can run at the same time, letting
the Application Broker balance the load. As multiple users invoke
Application Dispatcher programs, multiple servers can be used to improve
application performance. An optional component called the Application
Load Manager can be added to assist the Application Broker in balancing
the load.
Instead
of using the socket service method of running the Application Server,
you can use the launch service, which starts a new server for each
request. Although this method can require more time than the socket
service because of the Application Server start-up time, it is easier
to administer and provides some security advantages.
Using
the Application Load Manager, the pool service starts servers from
the pool as needed to handle queued jobs. When a job completes, the
server becomes available for new requests until an optional idle time-out
is reached, at which time the server shuts down.