Feature: Spawning jobs/tasks to a target thread #31
Description
One feature that has added a notable amount of the complexity to bevy_tasks is how !Send constraints within Bevy's ECS are handled. These resources force the task to only be run from a specific thread, but may be scheduled from any other thread. bevy_tasks addresses this by creating a thread-local ThreadExecutor and then weaving it in Scope tasks' polling. This is further refined in bevyengine/bevy#20331 into a dedicated per-thread queue that is separately polled by every thread when looking for new work.
For Forte to be viable as a replacement for bevy_tasks, there needs to be some support for this feature, ideally with a API as follows:
// `thread_id` may denote a Worker or even a temporary worker that periodically joins the ThreadPool.
// This function should panic if a non-worker thread is provided.
impl Worker {
pub fn spawn_to_thread<F: FnOnce()>(thread_id: ThreadId, f: F);
pub fn spawn_future_to_thread<T, Fut: Future<Output = T>>(thread_id: ThreadId, future: Fut) -> Task<T>;
}
impl<'a> Scope<'a> {
pub fn spawn_to_thread<F: FnOnce(Scope<'a>)>(thread_id: ThreadId, f: F) -> Task<T>;
pub fn spawn_future_to_thread<T, Fut: Future<Output = T>>(thread_id: ThreadId, future: Fut) -> Task<T>;
}Since these jobs can only be run on the target thread, these jobs ideally should be prioritized over other Send jobs that end up in the same thread's queue.