Event-driven servers

For many purposes threads are great, especially because we can still program in the familiar procedural, blocking-IO style. But they suffer from the drawback that they struggle when managing large numbers of connections simultaneously, because they are required to maintain a thread for each connection. Each thread consumes memory, and switching between threads incurs a type of CPU overhead called context switching. Although these aren't a problem for small numbers of threads, they can impact performance when there are many threads to manage. Multiprocessing suffers from similar problems.

An alternative to threading and multiprocessing is using the event-driven model. In this model, instead of having the OS automatically switch between active threads or processes for us, we use a single thread which registers blocking objects, such as sockets, with the OS. When these objects become ready to leave the blocking state, for example a socket receives some data, the OS notifies...