An Object Behavioral Pattern for Demultiplexing and Dispatching Handlers for Asynchronous Events

Modern operating systems provide multiple mechanisms for developing concurrent applications. Synchronous multithreading is a popular mechanism for developing applications that perform multiple operations simultaneously. However, threads often have high performance overhead and require deep knowledge of synchronization patterns and principles. Therefore, an increasing number of operating systems support asynchronous mechanisms that provide the benefits of concurrency while alleviating much of the overhead and complexity of multi-threading. The Proactor pattern presented in this paper describes how to structure applications and systems that effectively utilize asynchronous mechanisms supported by operating systems. When an application invokes an asynchronous operation, the OS performs the operation on behalf of the application. This allows the application to have multiple operations running simultaneously without requiring the application to have a corresponding number of threads. Therefore, the Proactor pattern simplifies concurrent programming and improves performance by requiring fewer threads and leveraging OS support for asynchronous operations.