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Oliver Gould
4236b5a668
`tokio::task` enforces a cooperative scheduling regime that can cause `oneshot::Receiver::poll` to return pending after the sender has sent an update. `ReadyCache` uses a oneshot to notify pending services that they should not become ready. When a cancelation is not observed, the ready cache return service instances that should have been canceled, which breaks assumptions and causes an invalid state. This branch replaces the use of `tokio::sync::oneshot` for canceling pending futures with a custom cancelation handle using an `AtomicBool` and `futures::task::AtomicWaker`. This ensures that canceled `Pending` services are always woken even when the task's budget is exceeded. Additionally, cancelation status is now always known to the `Pending` future, by checking the `AtomicBool` immediately on polls, even in cases where the canceled `Pending` future was woken by the inner `Service` becoming ready, rather than by the cancelation. Fixes #415 Signed-off-by: Oliver Gould <ver@buoyant.io> Co-authored-by: Eliza Weisman <eliza@buoyant.io>