From: Brian Candler <b.candler@...>
Date: 2010-05-19T01:00:57+09:00
Subject: Re: Asynchronous HTTP request

Daniel DeLorme wrote:
> Brian Candler wrote:
>> So you didn't want a Thread, but you'll happily use a Fiber...
> 
> Well, yes, a Fiber is just a coroutine, nothing like a thread.

Except that the semantics of Threads are well defined. You start them, 
they do stuff, you join them.

Are you saying that a Fiber will return control to you when it blocks 
due to lack of data on a socket, as well as when the Fiber explicitly 
"yields"? What value does it return to you in the blocking case?

Testing suggests otherwise.

$ cat ert.rb
p1, p2 = IO.pipe

f = Fiber.new do
  puts "Starting fiber"
  p1.gets
  puts "Ending fiber"
end

sleep 0.5
puts "Point A"
f.resume
puts "Point B"

$ ruby19 ert.rb
Point A
Starting fiber

As far as I can see: the fiber starts processing when f.resume is 
called, but blocks when p1.gets is called.

So AFAICS, your code which thinks it can do work while the the HTTP 
request is running, doesn't. Rather, the HTTP request is not sent at all 
until the Fiber#resume is called, and at that point it will block as 
necessary until the whole response is received.
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