Re: [Caml-list] Question about Lwt/Async

[Malcolm Matalka <mmatalka@gmail.com>]

Yotam Barnoy <yotambarnoy@gmail.com> writes:

> Hi all
>
> I'm thinking about my next project in OCaml, and I'm wondering how many
> users of OCaml currently use Lwt or Async regularly.
>
> One of the advantages of OCaml over Haskell (which I'm not crazy about) is
> the fact that you don't have to constantly be stuck inside a monad.
> However, once you want to use these user-level threading libraries, you're
> essentially tied to a monad. It also means that the usage of any other
> monad from Lwt/Async code is out -- OCaml doesn't have the monad
> transformer infrastructure to layer monads easily as far as I can tell (am
> I wrong?). I mean, even in Haskell using Monad Transformers is a pain (IMO).
>
> Also, what happens to general utility functions that aren't rewritten for
> Async/Lwt -- as far as I can tell, being in non-monadic code, they will
> always starve other threads, since they cannot yield to another Async/Lwt
> thread. Is this perception correct? If so, this seems to imply that you
> either write your code to cooperate within these frameworks and suffer the
> monad, or don't, and make it near-impossible for Lwt/Async users to make
> use of your code.
>
> I would like to get an idea of the usage level of these libraries, as well
> as the burden of writing compatible code, any difficulties etc. Also, I'd
> like to get a sense of the domains that benefit from these libraries. Some
> domains (such as gaming) traditionally involve a continuous main loop, and
> would thus only suffer from the additional overhead of queuing in these
> libraries.
>
> -Yotam

I mostly use Async.  However, I think most usage of Lwt or Async
requires doing as little as possible in these frameworks and using them
to orchestrate other functions.  For example, I usually try to separate
parsing of a network protocol from the reading and writing of the bytes.