Add support for typed task Labels. #138

jorajeev · 2024-03-04T01:33:46Z

PR98 added support for associated a single untyped Tag with each task and thread. As we've gained experience with Tags, we've increasingly felt a need to have a mechanism that is both better typed, and allows more than one tag to be associated with tasks. This commit introduces Labels, which are inspired by Extensions in the http crate. Users can attach any set of Labels to a task or thread, with the only caveat being that there can be at most one Label for a given type T. This is not too onerous a restriction, since one can use the common newtype idiom to easily work around this.

For tracing, we also provide a newtype TaskName that can be converted to and from a String. If the TaskName label is set for a task, tracing output will show the TaskName (in addition to the TaskId) to make logs easier to read.

Since the current functionality provided by Tag is superseded by Labels, we also mark Tag as deprecated. They will be removed in a future release.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

src/current.rs

src/runtime/task/labels.rs

tests/basic/labels.rs

src/runtime/task/mod.rs

tests/basic/labels.rs

sarsko · 2024-03-04T21:13:08Z

(discussed with Rajeev, posting here to not forget it / have an entry where it may be discussed)

One thing which is lost from Labels vs Tags is the ability to gain more information than a simple string in the tracing output from Shuttle. There is a question of whether there should be the possibility to have more information logged, for instance by exposing a way to provide a closure with a type signature ala &[Label] -> Debug.

sarsko · 2024-03-04T22:20:54Z

Send + Sync bound can be removed: 9822138

jorajeev · 2024-03-05T01:35:45Z

Summary of changes since the first reviewed version:

renamed LabelFn -> ChildLabelFn, and changed the function signature to Fn(TaskId, &mut Labels), because there are situations where the TaskId is useful
removed Send + Sync requirement for types usable as Labels
removed the clearing of all Labels at the beginning of an execution (the clearing is already done in ExecutionState::cleanup)

jamesbornholt

just docs nits

src/current.rs

src/runtime/task/labels.rs

src/current.rs

src/runtime/task/mod.rs

src/current.rs

src/runtime/task/mod.rs

[PR98](awslabs#98) added support for associated a single untyped `Tag` with each task and thread. As we've gained experience with Tags, we've increasingly felt a need to have a mechanism that is both better typed, and allows more than one tag to be associated with tasks. This commit introduces `Labels`, which are inspired by `Extensions` in [the http crate](https://docs.rs/http/latest/http/struct.Extensions.html). Users can attach any set of Labels to a task or thread, with the only caveat being that there can be at most one Label for a given type T. This is not too onerous a restriction, since one can use the common [newtype idiom](https://doc.rust-lang.org/rust-by-example/generics/new_types.html) to easily work around this. For tracing, we also provide a newtype `TaskName` that can be converted to and from a `String`. If the `TaskName` label is set for a task, tracing output will show the `TaskName` (in addition to the `TaskId`) to make logs easier to read. Since the current functionality provided by `Tag` is superseded by `Labels`, we also mark `Tag` as deprecated. They will be removed in a future release.

jorajeev force-pushed the add-labels branch from 8eaa694 to 31ff5f7 Compare March 4, 2024 01:48