Simplifying Task Scheduling in Tokio with LocalRuntime

Core Problem

Currently, spawning !Send tasks on Tokio requires combining a current-thread runtime and LocalSet, leading to performance overhead and unexpected behavior.

Solution & Analysis

Introducing LocalRuntime

To address the issue, we propose introducing a new type called LocalRuntime. This type behaves like a current-thread Runtime, but with additional features:

struct LocalRuntime {
    // ...
}

impl Runtime for LocalRuntime {
    fn new() -> Self {
        // ...
    }

    // ...
}

impl LocalSet for LocalRuntime {
    // ...
}

Benefits of LocalRuntime

The proposed LocalRuntime has several benefits:

• It is !Send, allowing direct spawning of !Send tasks onto the runtime.
• Within a LocalRuntime, tokio::spawn and spawn_local have identical behavior, making it easier to manage tasks.
• Tasks spawned using spawn_local are scheduled in the same way as normal tokio::spawn tasks.

struct LocalSet {
    runtime: LocalRuntime,
}

impl LocalSet for LocalRuntime {
    fn new() -> Self {
        LocalRuntime { /* ... */ }
    }

    // ...
}

Comparison with Current Implementation

The proposed LocalRuntime provides a more efficient and intuitive way to manage tasks in Tokio. By introducing this new type, we can simplify the task scheduling process and reduce performance overhead.

Conclusion

Replacing the current runtime+local set implementation with LocalRuntime offers several benefits, including improved efficiency, reduced complexity, and enhanced developer experience. This proposal aims to enhance the overall Tokio ecosystem and provide a better foundation for building high-performance asynchronous applications.

Reference

• Source