Mason Protter (Feb 28 2024 at 14:25): Mason Protter (Feb 28 2024 at 14:25):Anyone know how to deal with this? I'm trying to use remote_call (or any other form of distributed computing) from within a package and I just can't get it to work because it complains about not being able to find the package.
Here's a MWE:
julia> module Foos
struct Foo end
using Distributed
f() = let p = only(addprocs(1))
x = remotecall_fetch(p) do
Foo()
end
rmprocs([p])
x
end
end
Main.Foos
julia> Foos.f()
ERROR: On worker 2:
UndefVarError: `Foos` not defined
Stacktrace:
[1] deserialize_module
@ ~/julia-1.10/usr/share/julia/stdlib/v1.10/Serialization/src/Serialization.jl:997
[2] handle_deserialize
@ ~/julia-1.10/usr/share/julia/stdlib/v1.10/Serialization/src/Serialization.jl:896
You defined Foo in your process (1), but not the newly added process. Since Julia is nominally typed, and its full name is Foos.Foo, you'll get an error.
Sergio Vargas (Feb 28 2024 at 14:46):You'd have to import shared types with @everywhere
Mason Protter (Feb 28 2024 at 14:51):I don't think that's right. Notice that the error isn't that Foo isn't defined, it's that Foos is not defined
Mason Protter (Feb 28 2024 at 14:58):Let's step away from the REPL version with a local module and do a package:
> cat Foos/src/Foos.jl
module Foos
using Distributed
f() = let p = only(addprocs(1))
x = remotecall_fetch(p) do
1
end
rmprocs([p])
x
end
end # module Foos
> cat Foos/Project.toml
name = "Foos"
uuid = "378b42d5-b922-4ee0-b574-33ae726347f8"
version = "0.1.0"
[deps]
Distributed = "8ba89e20-285c-5b6f-9357-94700520ee1b"
i.e. a very simple little package that just creates a process, runs a function that does nothing but return 1, and then deletes that process.
Now here's what I see if I try to use it:
> julia -q --project=./Foos
julia> using Foos
julia> Foos.f()
ERROR: On worker 2:
KeyError: key Foos [378b42d5-b922-4ee0-b574-33ae726347f8] not found
Stacktrace:
[1] getindex
@ ./dict.jl:498 [inlined]
[2] macro expansion
@ ./lock.jl:267 [inlined]
[3] root_module
@ ./loading.jl:1878
[4] deserialize_module
@ ~/julia-1.10/usr/share/julia/stdlib/v1.10/Serialization/src/Serialization.jl:994
[5] handle_deserialize
@ ~/julia-1.10/usr/share/julia/stdlib/v1.10/Serialization/src/Serialization.jl:896
[...]
Maybe you need to do using Foos on the worker first?
Sukera (Feb 28 2024 at 15:11):both your REPL & package MWE share that the name Foos already exists; in the REPL example because it's in Main, in the package example because you have using Foos first
Mason Protter (Feb 28 2024 at 15:15):Changing the function to
f() = let p = only(addprocs(1))
x = remotecall_fetch(p) do
eval(:(using Foos))
1
end
rmprocs([p])
x
end
doesn't seem to eliminate the error
Mason Protter (Feb 28 2024 at 15:27):Hm, okay, so I managed to get my actual usecase working by using what feels like an excessive amount of indirection. I did something like this:
module Foos
using Distributed
struct Foo
x
end
function _f(foo)
Foo(foo.x + 1)
end
f(foo) = let p = only(addprocs(1))
Distributed.remotecall_eval(
Main, p, :(using Foos))
x =Distributed.remotecall_eval(Main, p, :(Foos._f($foo)))
rmprocs([p])
x
end
end # module Foos
Without all that indirection, I guess it was unhappy about me passing around structs that were defined in Foos, in particular, I needed totally separate calls to remotecall_eval to make it work.
Mason Protter (Feb 28 2024 at 15:27):very weird
Notification Bot (Feb 28 2024 at 15:35):Mason Protter has marked this topic as resolved.
Sukera (Feb 28 2024 at 15:40):yeah, that's what I was thinking of; you need the additional remotecall_eval for world age purposes, I think
Last updated: Nov 01 2025 at 04:39 UTC