Network Programming with Perl

By Lincoln  D.  Stein

Slots : 1

Chapter 15. Preforking and Prethreading

Chapters 9 through 12 demonstrated several techniques for handling concurrent incoming connections to a server application:

1. Serial The server processes connections one at a time. This is typical of UDP servers, because each transaction is short-lived, but it is distinctly uncommon for connection-oriented servers.

2. Accept-and-fork The server accepts connections and forks a new child process to handle each one. This is the most common server design on UNIX systems and includes servers launched by the inetd super daemon.

3. Accept-and-thread The server accepts connections and creates new threads of execution to handle each one. This can have better performance than accept-and-fork because the system overhead to launch new threads is often less than it would be to launch new processes.

4. Multiplexed The server uses select() and its own session state maintenance logic to interweave the processing of multiple connections. This has excellent performance because there's no process-launching overhead, but there is the cost of increased code complexity, particularly if nonblocking I/O is used.

In most cases, one of these four architectures will meet your requirements. However, in certain circumstances, particularly those in which the server must manage a heavy load, you should consider more esoteric designs. This chapter discusses two additional server architectures: preforking and prethreading.