Malt.jl

Malt is a multiprocessing package for Julia. It is used by Pluto.jl to manage the Julia process that notebook code is executed in, as a replacement to Distributed.

You can find more information on the documentation.

julia> import Malt

julia> worker = Malt.Worker();

julia> Malt.remote_eval_fetch(worker, :(1 + 1))
2

julia> Malt.remote_eval_fetch(worker, :(rand(5))) |> sum
3.0618168580350966

Example of running code asynchonously, and interrupting the process:

julia> task = Malt.remote_eval(worker, :(sleep(100)))
Task (runnable) @0x0000023539e7f460

julia> Malt.interrupt(worker)

julia> wait(task)
ERROR: TaskFailedException
Stacktrace:
 ...
    nested task error: Remote exception from Malt.Worker on port 9584 with PID 17584:

    InterruptException:
    Stacktrace:
      ...

julia> Malt.stop(worker);

julia> Malt.isrunning(worker)
false

Malt.jl vs Distributed

Malt.jl is inspired by the Distributed standard library, but with a focus on process sandboxing, not distributed computing. Important differences are:

API changes

Malt.jl has different function names, see our documentation.

One important addition is public API for evaluating an Expr:

worker = Malt.Worker()
Malt.remote_eval_fetch(worker, :(sqrt(123)))

Nested use

With Malt.jl, any worker process can also be a host process to its own workers.

In Distributed, only "process 1 can add or remove workers". Malt.jl does not have this limiation. This means that Malt.jl workers can use Distributed (and Malt.jl) like a regular Julia process.

Process isolation

Malt.jl worker processes do not inherit ENV variables, command-line arguments or the Pkg environment from their host.

Interrupt on Windows

Malt.jl supports interrupting a worker process on Windows, not just on UNIX.

Homogenous computing

Malt.jl does not have API like @everywhere or Distributed.procs: Malt is not the right tool for homogenous computing.

Exception handling

Exceptions in Malt.jl workers are converted to plaintext before being rethrown in the host.

The original exception object is only available to the worker. In Distributed, the original exception object is serialized and rethrown to the host.

Faster launch

Malt.jl launches workers >50% faster.

julia> @time Distributed.addprocs(1);
  2.064801 seconds (11.63 k allocations: 1.093 MiB, 1.08% compilation time)

julia> @time Malt.Worker();
  0.964955 seconds (537 allocations: 308.734 KiB)

Limitations

In contrast to Distributed.jl, Malt.jl currently does not support launching workers on another machine (e.g. SSH remote workers).

Sponsors

Development of Malt.jl is sponsored by:

	JuliaHub enables the creation and editing of Pluto notebooks on the cloud!
	Google Summer of Code 2022 allowed Sergio A. Vargas to join us for a summer to develop Malt.jl! More details here.