14. Synchronous and Asynchronous Calls

• If a caller sends a synchronous message...

  • ...the caller must wait until the message is done.

  • For example: invoking a subroutine.

• If a caller sends an asynchronous message...

  • ...the caller can continue processing: no need to wait for a response.

  • For example: multithreaded applications and message-oriented middleware.

• Asynchrony

  • gives better responsiveness

  • reduces coupling

  • but is much harder to debug.