Module Duppy

module Duppy: sig .. end

Advanced scheduler and monad for server-oriented programming.

The bars could not hold me; Force could not control me now. They try to keep me down, yeah! But Jah put I around. (...) Let me tell you this - I'm a duppy conqueror !

Lee "Scratch" Perry & Bob Marley - Duppy conqueror

Duppy task scheduler for OCaml.

Duppy is a task scheduler for ocaml. It implements a wrapper around Unix.select.

Using Duppy.Task, the programmer can easily submit tasks that need to wait on a socket even, or for a given timeout (possibly zero).

With Duppy.Async, one can use a scheduler to submit asynchronous tasks.

Duppy.Io implements recursive easy reading and writing to a Unix.file_descr

Finally, Duppy.Monad and Duppy.Monad.Io provide a monadic interface to program server code that with an implicit return/reply execution flow.

The scheduler can use several queues running concurently, each queue processing ready tasks. Of course, a queue should run in its own thread.

type 'a scheduler

A scheduler is a device for processing tasks. Several queues might run in different threads, processing one scheduler's tasks.

'a is the type of objects used for priorities.

exception Panic of exn

Panic exception is raised when duppy's event loops has crashed. This exception should be considered a MAJOR FAILURE. All current non-ready tasks registered for the calling scheduler are dropped. You may restart Duppy's queues after it is raised but it should only be used to terminate the process diligently!!

val create : ?compare:('a -> 'a -> int) -> unit -> 'a scheduler

Initiate a new scheduler

compare : the comparison function used to sort tasks according to priorities. Works as in List.sort

val queue : ?log:(string -> unit) ->
       ?priorities:('a -> bool) -> 'a scheduler -> string -> unit

queue ~log ~priorities s name starts a queue, on the scheduler s only processing priorities p for which priorities p returns true.

Raises Panic exception if exception was raised while executing the main event loop.

Several queues can be run concurrently against s.

log : Logging function. Default: Printf.printf "queue %s: %s\n" name

priorities : Predicate specifying which priority to process. Default: fun _ -> _ -> true

val stop : 'a scheduler -> unit

Stop all queues running on that scheduler, causing them to return.

module Task: sig .. end

Core task registration.

module Async: sig .. end

Asynchronous task module

module Io: sig .. end

Easy parsing of Unix.file_descr.

module Monad: sig .. end

Monadic interface to Duppy.Io.

Some culture..

Duppy is a Caribbean patois word of West African origin meaning ghost or spirit. Much of Caribbean folklore revolves around duppies. Duppies are generally regarded as malevolent spirits. They are said to come out and haunt people at night mostly, and people from the islands claim to have seen them. The 'Rolling Calf', 'Three footed horse' or 'Old Higue' are examples of the more malicious spirits.

http://en.wikipedia.org/wiki/Duppy