The programming model of vibe.d

The key to the scalability of vibe.d is the use of asynchronous I/O in combination with fibers.

What is a fiber?

Modern operating systems implement preemptive multitasking. A thread runs until its time slice is exhausted or it must wait for an I/O operation. Then the kernel chooses a different thread to run. Ultimately, the scheduler in the kernel controls the threads.

In contrast, fibers are a form of cooperative multitasking. As the name implies, cooperative multitasking requires some help from the user functions. A function runs up to a point where the developer decides would be a good place to run another task. Usually, a library function named yield() is called, which continues the execution of another function. This is best shown with an example. Here is a simplified version of the classic producer-consumer pattern:

import std.stdio;
import std.math;
import core.thread;

private int goods;
private bool exit;

void producerFiber()
{
  foreach (i; 0..3)
 ...