Module Procord_task

module Procord_task: sig .. end

Procord task description.

To use Procord, you must first describe a task.

A task is basically a function to execute, plus some serializing functions for inputs, outputs and exceptions.

Default serializing functions use the Marshal module of the standard library. It should only be used for quick prototyping or if you really know what you are doing.

Tasks, From the Worker Point of View

type ('a, 'b) worker_task

Worker tasks contain the information needed by the worker process.

val make_worker_task : ?read_input:(string -> 'a) ->
       ?write_output:('b -> string) ->
       ?write_exception:(exn -> string) ->
       string -> ('a -> 'b) -> ('a, 'b) worker_task

Make a worker_task.

The worker needs the following information.

read_input : Deserialization function for input values. This should be compatible with the write_input counterpart given to make_delegated_task.

write_output : Serialization function for output values. This should be compatible with the read_output counterpart given to make_delegated_task.

write_exception : Serialization function for exceptions. This should be compatible with the read_exception counterpart given to make_delegated_task. Marshaling is not used: if unspecified, the main program will receive a Worker_unknown_exception error.

The string argument is the name of the task. It should be the same as the one given to make_delegated_task. A given worker cannot run two tasks with the same name.

The last argument is the function that the tasks runs.

If read_input or write_output raises an exception, it will be passed to write_exception for transmission to the main program.

If write_exception raises an exception, it will be serialized as a Worker_unknown_exception using Printexc.

val read_input : ('a, 'b) worker_task -> string -> 'a

Get the input deserialization function of a worker task.

val write_output : ('a, 'b) worker_task -> 'b -> string

Get the output serialization function of a worker task.

val write_exception : ('a, 'b) worker_task -> exn -> string

Get the exception serialization function of a worker task.

val run : ('a, 'b) worker_task -> 'a -> 'b

Get the function that a worker task runs.

val worker_task_name : ('a, 'b) worker_task -> string

Get the name of a worker task.

Tasks, From the Main Program Point of View

type ('a, 'b) delegated_task

Delegated tasks contain the information needed by the main program.

Type parameter 'a is the type of input values, and type parameter 'b is the type of output values.

val make_delegated_task : ?write_input:('a -> string) ->
       ?read_output:(string -> 'b) ->
       ?read_exception:(string -> exn) ->
       string -> ('a, 'b) delegated_task

Make a delegated_task.

The worker needs the following information.

write_input : Serialization function for input values. This should be compatible with the read_input counterpart given to make_worker_task.

read_output : Deserialization function for output values. This should be compatible with the write_output counterpart given to make_worker_task.

read_exception : Deserialization function for exceptions. This should be compatible with the write_exception counterpart given to make_worker_task. If unspecified, received exceptions will be handled as Worker_unknown_exception errors.

The string argument is the name of the task. It should be the same as the one given to make_worker_task.

If write_input or read_output raises an exception, it will result in a Worker_connection_failed error. If read_exception is unspecified or raises an exception, it will result in a Worker_unknown_exception error.

val write_input : ('a, 'b) delegated_task -> 'a -> string

Get the input serialization function of a delegated task.

val read_output : ('a, 'b) delegated_task -> string -> 'b

Get the output deserialization function of a delegated task.

val read_exception : ('a, 'b) delegated_task -> (string -> exn) option

Get the exception deserialization function of a delegated task, if any.

val delegated_task_name : ('a, 'b) delegated_task -> string

Get the name of a delegated task.

Tasks, From Both Points of View

val make : ?read_input:(string -> 'a) ->
       ?write_input:('a -> string) ->
       ?read_output:(string -> 'b) ->
       ?write_output:('b -> string) ->
       ?read_exception:(string -> exn) ->
       ?write_exception:(exn -> string) ->
       string ->
       ('a -> 'b) ->
       ('a, 'b) worker_task * ('a, 'b) delegated_task

Make a worker_task and a delegated_task.

Using this function ensures the task name is the same in the worker_task and in the delegated_task.