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This refactors I/O registration in a few ways: - Cleans up the cached readiness in `PollEvented`. This cache used to be helpful when readiness was a linked list of `*mut Node`s in `Registration`. Previous refactors have turned `Registration` into just an `AtomicUsize` holding the current readiness, so the cache is just extra work and complexity. Gone. - Polling the `Registration` for readiness now gives a `ReadyEvent`, which includes the driver tick. This event must be passed back into `clear_readiness`, so that the readiness is only cleared from `Registration` if the tick hasn't changed. Previously, it was possible to clear the readiness even though another thread had *just* polled the driver and found the socket ready again. - Registration now also contains an `async fn readiness`, which stores wakers in an instrusive linked list. This allows an unbounded number of tasks to register for readiness (previously, only 1 per direction (read and write)). By using the intrusive linked list, there is no concern of leaking the storage of the wakers, since they are stored inside the `async fn` and released when the future is dropped. - Registration retains a `poll_readiness(Direction)` method, to support `AsyncRead` and `AsyncWrite`. They aren't able to use `async fn`s, and so there are 2 reserved slots for those methods. - IO types where it makes sense to have multiple tasks waiting on them now take advantage of this new `async fn readiness`, such as `UdpSocket` and `UnixDatagram`. Additionally, this makes the `io-driver` "feature" internal-only (no longer documented, not part of public API), and adds a second internal-only feature, `io-readiness`, to group together linked list part of registration that is only used by some of the IO types. After a bit of discussion, changing stream-based transports (like `TcpStream`) to have `async fn read(&self)` is punted, since that is likely too easy of a footgun to activate. Refs: #2779, #2728
Examples of how to use Tokio
This directory contains a number of examples showcasing various capabilities of
the tokio crate.
All examples can be executed with:
cargo run --example $name
A good starting point for the examples would be hello_world
and echo. Additionally the tokio website contains
additional guides for some of the examples.
For a larger "real world" example, see the mini-redis repository.
If you've got an example you'd like to see here, please feel free to open an issue. Otherwise if you've got an example you'd like to add, please feel free to make a PR!