Design And Development Of Concurrent Computing For Web Application Servers

Web servers, integrated with the traditional middleware, have been playing an important role in the advancement of the Internet. Because a web server needs to handle a large number of concurrent requests form the distributed applications, its concurrent computing environment, being an essential component of the web server, is responsible for scheduling requests and balancing loads, as well as providing programmable asynchronous multithreading interfaces to the developers of distributed applications. In the meantime, web servers should provide complicated QoS guarantees to various commercial websites, presenting a new requirement to the concurrent computing environment.Conventionally, the concurrency of web servers is implemented individually, and each module manages its own thread pools. No or few multithreading programming interface is available. Obviously, it cannot satisfy the increasingly complicated service demands. Since CommonJ provides a multithreading programming model based on WorkManager and this model supports concurrent scheduling, improving the efficiency and security performance of the system, it brings forward an opportunity to implement a brand new concurrent computing environment for web servers.A three layer concurrent computing framework, OnceAs Work Manager (OWM), is proposed on the basis of WorkManager. The middle layer of the web server uniformly manages all applications and concurrent tasks submitted by components and roles. This framework provides complete asynchronous programming interfaces to web server and application developers, as well as realize the maximum/minimum concurrent threading restrictions on demand, multiple priority constraints, role constraints in context and system load control. The above functionalities support the QoS requirements.The proposal has been applied in web server OnceAs. The functional and performance tests for this server demonstrate that the designed concurrent environment is able to satisfy the performance requirements of web server OnceAs, and provide various QoS guarantees.