CODEWITHSUNDEEP
multithreadingrust
ElefEnt
ElefEnt

Reputation: 2127

How do I share handlers between threads?

I am writing a multithreaded webserver and basically I need to copy a Vec<Handler> of user-provided handler objects across multiple threads on server startup. I tried several approaches:

1) Define Handler as a trait with a fn process(&mut self, Request) -> Response method. Users would implement it for each handler struct. This approach is very common in languages like C++ or python. The problem is that rust doesn't allow me to copy or clone a trait object as it would imply the Sized bound on it which is forbidden on trait objects.

2) Define Handler as a Box<FnMut(Request) -> Response>. This doesn't work as closures are not copyable.

3) I could share the same objects between threads but this makes very little sense to me as I would need a mutex which would introduce useless contention when I actually just need separate copies across threads.

How can I implement this properly?

Upvotes: 1

Views: 111

Answers (1)

Matthieu M.
Matthieu M.

Reputation: 299890

The simplest solution is to request the user to define a clone method.

trait Handler {
    fn process(&mut self, r: Request) -> Response;
    fn duplicate(&self) -> Box<Handler>;
}

And then you can copy your Vec<Box<Handler>> quite easily.

Upvotes: 1

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