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Module Netmcore_process

module Netmcore_process: sig .. end
Statically typed processes

This module provides a slightly higher-level view on processes, but is also a bit more restricted than the primitives in Netmcore.

Please read Netmcore_basics for an introduction into using this module. There is also Netmcore_tut with more advanced techniques.

type 'a fork_point 
A fork point can start a new process with argument 'a
type 'b join_point 
A join point can wait until a process finishes with a result 'b
val def_process : ('a -> 'b) -> 'a fork_point * 'b join_point
let (fp,jp) = def_process proc: Defines a process (which must happen in the master process), so that:

  • let pid = start fp arg: Starts the new process and passes the argument arg to it. The process runs proc arg which will finally result in a value r
  • let r_opt = join jp pid: Waits until the process identified by pid finishes, and returns the result as r_opt = Some r. On error, it returns None.
def_process should be called at module initialization time before any process is started. This interface is not designed for calling def_process later.
val start : ?inherit_resources:Netmcore.inherit_request ->
'a fork_point -> 'a -> Netmcore.process_id
let pid = start fp arg: Starts a new process at the fork point fp with argument arg. This means that the process is forked from the master process, and that the value of arg is sent to it using Marshal. The returned process ID is Netmulticore's own ID and not to be confused with the ID assigned by the operating system.

Option inherit_resources: Certain resources are only accessible by the process when they are inherited to it. This is the case for `Posix_shm_preallocated. This can be set to `All to inherit all inheritable resources, or to `Resources l to only inherit the resources of l. By default, no resources are inherited.

val join : 'b join_point -> Netmcore.process_id -> 'b option
let r_opt = join jp pid: Waits until the process pid finishes, and uses the join point jp to extract the result. The result is returned as Some r on success, and None on error. Result values are transmitted from the joining process to this function using Marshal. Errors include uncaught exceptions as well as unexpected process termination (exit, signal).

If the process referenced by pid is not an instance that belongs to jp, the function will fail.

This function must not be called from the master process (which is not allowed to block until a result is available).

val join_nowait : 'b join_point -> Netmcore.process_id -> 'b option
Like join, but it is not waited for the termination of the process. If the process is not yet done, this function returns None. It also returns None if the process terminated with an error or did not set a result value for other reasons.

Unlike join, this function can be called in the master process.

val release_fork_point : 'a fork_point -> unit
Releases a fork point so it is deleted from the internal resource table.
val release_join_point : 'b join_point -> unit
Releases a join point so it is deleted from the internal resource table.
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