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d456706528
## Motivation In many cases, it is desirable to spawn a set of tasks associated with keys, with the ability to cancel them by key. As an example use case for this sort of thing, see Tower's [`ReadyCache` type][1]. Now that PR #4530 adds a way of cancelling tasks in a `tokio::task::JoinSet`, we can implement a map-like API based on the same `IdleNotifiedSet` primitive. ## Solution This PR adds an implementation of a `JoinMap` type to `tokio_util::task`, using the `JoinSet` type from `tokio::task`, the `AbortHandle` type added in #4530, and the new task IDs added in #4630. Individual tasks can be aborted by key using the `JoinMap::abort` method, and a set of tasks whose key match a given predicate can be aborted using `JoinMap::abort_matching`. When tasks complete, `JoinMap::join_one` returns their associated key alongside the output from the spawned future, or the key and the `JoinError` if the task did not complete successfully. Overall, I think the way this works is pretty straightforward; much of this PR is just API boilerplate to implement the union of applicable APIs from `JoinSet` and `HashMap`. Unlike previous iterations on the `JoinMap` API (e.g. #4538), this version is implemented entirely in `tokio_util`, using only public APIs from the `tokio` crate. Currently, the required `tokio` APIs are unstable, but implementing `JoinMap` in `tokio-util` means we will never have to make stability commitments for the `JoinMap` API itself. [1]: https://github.com/tower-rs/tower/blob/master/tower/src/ready_cache/cache.rs Signed-off-by: Eliza Weisman <eliza@buoyant.io>
tokio-util
Utilities for working with Tokio.
License
This project is licensed under the MIT license.
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Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in Tokio by you, shall be licensed as MIT, without any additional terms or conditions.