Strategies for Cancelling Long-Running Rayon Tasks in Rust via RabbitMQ

I’m developing an executor in Rust to handle compute-intensive tasks as part of a larger web application. The executor receives jobs from RabbitMQ (using lapin) and processes various CPU-bound operations, which include some that internally utilize rayon. I’m aware that async can complicate rayon’s usage. Post-computation or task cancellation, it communicates results or cancellation status back to RabbitMQ.

The operations in question are out of my control, consisting mainly of long-running, parallel graph algorithms. I’m exploring strategies to cancel these tasks reactively through a separate RabbitMQ cancellation queue without rewriting the underlying libraries due to their (to my understanding) non-compatibility with async patterns and the general lack of built-in task cancellation support for safety reasons.

I’ve prototyped an executor using tokio, only to recognize the potential issues with rayon after the fact. The current cancellation strategy is based on tokio oneshot channels, which inefficiently drop tasks without liberating CPU resources. I am looking for advice on crafting an idiomatic executor that enables effective task cancellation and conforms to Rust’s safety guarantees.

Edit: I‘ll try to be more specific: Essentially, I am looking for a strategy to cancel (long-running, blocking, CPU-bound) tasks from another thread, effectively aborting the computation and freeing up the CPU. Gracefully signaling shutdown using a mechanism such as tokio‘s oneshot channel is not an option since I don‘t have control over the implementation of the long running operation.