From: "Ara.T.Howard" <Ara.T.Howard@...>
Date: 2005-10-04T22:40:28+09:00
Subject: Re: state of blocking/nonblocking I/O

On Tue, 4 Oct 2005, Tanaka Akira wrote:

> In article <3qctcuFecn8gU1@individual.net>,
>  "Robert Klemme" <bob.news@gmx.net> writes:
>
>> I have one question on this matter which I still don't understand (I'm not
>> so deep into C stdlib IO variants so please bear with me): why would anybody
>> want to use nonblocking IO (on the Ruby level, e.g. IO#read might not have
>> read anything on return even if the stream is not closed) in the light of
>> Ruby threads?  I mean, with that one would have to build the multiplexing in
>> Ruby which is already present in the interpreter with multiple Ruby threads?
>> Are there situations that I'm not aware of where this is useful / needed?
>
> It is an interesting question I also have.
>
> I asked it several times, so I know some answers.
>
> 1. GUI framework has its own event driven framework.
>
>  If a callback blocks, it blocks entire GUI.  It is not
>  acceptable.
>
> 2. High performance network server has its own event driven
>   framework.
>
>  Some high performance network servers use an application
>  level event driven framework.  If an event handler blocks,
>  it blocks entire application.  It is not acceptable.
>
>  However I'm not sure that it is appropriate to implement
>  a high performance server in Ruby.
>
> If an application level event driven framework is used,
> application level nonblocking I/O operations are required.
>
> If there are other usages, I'd like to know.

it's sort of the same thing as 2, but network intense clients might me written
more easily too...  i've written code that was managing 100s of ssh connection
for example.  i could have used threads but it was easier/more responsive to
just have an array of pipes and non-blocking reads.

the only other thing i can think of is any time you may actually be fine
blocking on a read, but wish to remain aware of time - eg. you don't want to
block too long - and here something like readpartial is great.

-a
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