Queuing network
WAS contains interrelated components that must be harmoniously tuned to support the custom needs of your end-to-end e-business application. These adjustments help the system achieve maximum throughput while maintaining the overall stability of the system.
This group of interconnected components is known as a queuing network. These queues or components include...
- Network
- Web server
- Web container
- EJB container
- data source
- Connection manager to a custom back-end system
Each of these resources represents a queue of requests waiting to use that resource.
Various queue settings include:
IBM HTTP Server MaxClients for operating systems such as AIX or Linux and ThreadsPerChild for Windows NT and Windows 2000 systems Web container Maximum size described in Thread pool settings, MaxKeepAliveConnections and MaxKeepAliveRequests Object Request Brokers Tuning appservers. Data source connection pooling Connection pooling. Statement cache size
Most of the queues that make up the queuing network are closed queues. A closed queue places a limit on the maximum number of requests present in the queue, while an open queue has no limit. A closed queue supports tight management of system resources. For example, the Web container thread pool setting controls the size of the Web container queue. If the average servlet running in a Web container creates 10 MB of objects during each request, a value of 100 for thread pools limits the memory consumed by the Web container to 1 GB.
In a closed queue, requests can be active or waiting. An active request is doing work or waiting for a response from a downstream queue. For example, an active request in the Web server is doing work, such as retrieving static HTML, or waiting for a request to complete in the Web container. A waiting request is waiting to become active. The request remains in the waiting state until one of the active requests leaves the queue.
All Web servers supported by WAS are closed queues, as are data sources. You can configure Web containers as open or closed queues. In general, it is best to make them closed queues. EJB containers are open queues. If there are no threads available in the pool, a new one is created for the duration of the request.
If enterprise beans are called by servlets, the Web container limits the number of total concurrent requests into an EJB container, because the Web container also has a limit. The Web container limits the number of total concurrent requests only if enterprise beans are called from the servlet thread of execution. Nothing prevents you from creating threads and bombarding the EJB container with requests. Therefore, servlets should not create their own work threads.
Sub-topics
Queuing and clustering considerations
Queue configuration best practices
Related tasks
Manage Object Request BrokersTuning the application serving environment