TaskWorkers.jl

TaskWorkers.jl creates a loop that executes functions or closures sent to it. The main use is ensuring those functions will execute on the Task that the TaskWorker was started on. For example, this could be used to ensure that functions are executed on Julia's root Task.

The main purpose of this package is to facilitate interoperation of Julia with other software that may be confused with Julia's Tasks which do not copy the stack by default.

Installation

This package is currently not registered in the general Julia registry as significant prototyping is underway. To add from the Julia REPL:

]add https://github.com/mkitti/TaskWorkers.jl#master

Quick Usage and Demo

julia> Base.current_task() == Base.roottask
true

julia> using TaskWorkers

julia> TaskWorkers.startworker_and_repl()
               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.5.0 (2020-08-01)
 _/ |\__'_|_|_|\__'_|  |  Official https://julialang.org/ release
|__/                   |

julia> Base.current_task() == Base.roottask
false

julia> taskrun() do
           Base.current_task() == Base.roottask
       end
true

julia>

Extended Usage

Because of Julia's stack conventions for Tasks it may be necessary to ensure certain commands run on a certain Task, in particular the root Task (Base.roottask).

The following will start a new REPL on a new Task and start running a TaskWorker on the root Task:

using TaskWorkers
worker = TaskWorker()
@async(Base.run_main_repl(true,true,true,true,true)); sleep(1); start(worker)

A shortcut for the above is available as TaskWorkers.startworker_and_repl(). Replace Base.run_main_repl with any function which will continue on a new Task. The TaskWorker will take over the current Task with its execution loop.

From the newly created REPL you can then check to see which commands are running on the root Task

julia> Base.current_task() == Base.roottask
false

julia> taskrun(worker) do
           Base.current_task() == Base.roottask
       end
true

If worker is not specified (e.g. taskrun() do ... end), TaskWorkers.worker[] will be used. TaskWorkers.worker is a Ref{TaskWorker} can be populated manually or with these convenience functions:

• TaskWorkers.startworker()
• TaskWorkers.startworker_and_repl()

This is only meant as a convenience. Otherwise, it is recommended that you track your own global references to TaskWorkers.

Applications

This package was developed to help Julia interoperate with other software that depend In particular, this could be useful for use with JavaCall.jl.

Related Julia issues, pull requests, and packages

• JuliaLang/julia#31983 (JuliaLang/julia#31983)
• JuliaLang/julia#35726 (Create a Base.root_task method and document it)
• JuliaLang/julia#35048 (Allow the the REPL backend to run on the root Task; Merged as of Julia 1.5) ** Julia pre-1.5, consider https://github.com/mkitti/RootTaskREPL.jl