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//! This crate provides a mechanism for interrupting a `Stream`. //! //! Any stream can be wrapped in a [`Valved`], which enables it to be remotely terminated through //! an associated [`ValveHandle`]. This can be useful to implement graceful shutdown on "infinite" //! streams like a `TcpListener`. Once [`ValveHandle::close`] is called on the handle for a given //! stream's [`Valved`], the stream will yield `None` to indicate that it has terminated. //! //! ``` //! # extern crate stream_cancel; //! extern crate tokio; //! //! use stream_cancel::Valved; //! use tokio::prelude::*; //! use std::thread; //! //! let listener = tokio::net::TcpListener::bind(&"0.0.0.0:0".parse().unwrap()).unwrap(); //! let (exit, incoming) = Valved::new(listener.incoming()); //! //! let server = thread::spawn(move || { //! // start a tokio echo server //! tokio::run( //! incoming //! .map_err(|e| eprintln!("accept failed = {:?}", e)) //! .for_each(|sock| { //! let (reader, writer) = sock.split(); //! tokio::spawn( //! tokio::io::copy(reader, writer) //! .map(|amt| println!("wrote {:?} bytes", amt)) //! .map_err(|err| eprintln!("IO error {:?}", err)), //! ) //! }), //! ) //! }); //! //! // the server thread will normally never exit, since more connections //! // can always arrive. however, with a Valved, we can turn off the //! // stream of incoming connections to initiate a graceful shutdown //! exit.close(); //! server.join().unwrap(); //! ``` //! //! You can share the same [`ValveHandle`] between multiple streams by first creating a [`Valve`], //! and then wrapping multiple streams using [`Valve::Wrap`]: //! //! ``` //! # extern crate stream_cancel; //! extern crate tokio; //! //! use stream_cancel::Valve; //! use tokio::prelude::*; //! //! let (exit, valve) = Valve::new(); //! let listener1 = tokio::net::TcpListener::bind(&"0.0.0.0:0".parse().unwrap()).unwrap(); //! let listener2 = tokio::net::TcpListener::bind(&"0.0.0.0:0".parse().unwrap()).unwrap(); //! let incoming1 = valve.wrap(listener1.incoming()); //! let incoming2 = valve.wrap(listener2.incoming()); //! //! let mut rt = tokio::runtime::Runtime::new().unwrap(); //! rt.spawn( //! incoming1 //! .select(incoming2) //! .map_err(|e| eprintln!("accept failed = {:?}", e)) //! .for_each(|sock| { //! let (reader, writer) = sock.split(); //! tokio::spawn( //! tokio::io::copy(reader, writer) //! .map(|amt| println!("wrote {:?} bytes", amt)) //! .map_err(|err| eprintln!("IO error {:?}", err)), //! ) //! }), //! ); //! //! // the runtime will not become idle until both incoming1 and incoming2 have stopped (due to //! // the select). this checks that they are indeed both interrupted when the valve is closed. //! exit.close(); //! rt.shutdown_on_idle().wait().unwrap(); //! ``` #![deny(missing_docs)] extern crate futures; #[cfg(test)] extern crate tokio; use futures::{future::Shared, sync::oneshot, Async, Future, Poll, Stream}; /// A `Valved` is wrapper around a `Stream` that enables the stream to be turned off remotely to /// initiate a graceful shutdown. When a new `Valved` is created with [`Valved::new`], a handle to /// that `Valved` is also produced; when [`ValveHandle::close`] is called on that handle, the /// wrapped stream will immediately yield `None` to indicate that it has completed. #[derive(Clone, Debug)] pub struct Valved<S> { stream: S, valve: Shared<oneshot::Receiver<()>>, free: bool, } impl<S> Valved<S> { /// Make the given stream cancellable. /// /// To cancel the stream, call [`ValveHandle::close`] on the returned handle. pub fn new(stream: S) -> (ValveHandle, Self) { let (vh, v) = Valve::new(); (vh, v.wrap(stream)) } } /// A `Valve` is associated with a [`ValveHandle`], and can be used to wrap one or more /// asynchronous streams. All streams wrapped by a given `Valve` (or its clones) will be /// interrupted when [`ValveHandle::close`] is called on the valve's associated handle. #[derive(Clone, Debug)] pub struct Valve(Shared<oneshot::Receiver<()>>); impl Valve { /// Make a new `Valve` and an associated [`ValveHandle`]. pub fn new() -> (ValveHandle, Self) { let (tx, rx) = oneshot::channel(); (ValveHandle(tx), Valve(rx.shared())) } /// Wrap the given `stream` with this `Valve`. /// /// When [`ValveHandle::close`] is called on the handle associated with this valve, the given /// stream will immediately yield `None`. pub fn wrap<S>(&self, stream: S) -> Valved<S> { Valved { stream, valve: self.0.clone(), free: false, } } } /// A handle to a wrapped stream. /// /// If the `ValveHandle` is dropped without calling `close`, any streams wrapped by associated /// valves will *not* be interrupted. #[derive(Debug)] pub struct ValveHandle(oneshot::Sender<()>); impl ValveHandle { /// Close the valve for the associated stream, and make it immediately yield `None`. pub fn close(self) { self.0.send(()).unwrap(); } } impl<S> Stream for Valved<S> where S: Stream, { type Item = S::Item; type Error = S::Error; fn poll(&mut self) -> Poll<Option<Self::Item>, Self::Error> { if !self.free { match self.valve.poll() { Ok(Async::Ready(_)) => { // valve closed -- terminate stream return Ok(Async::Ready(None)); } Err(_) => { // valve handle was dropped -- let the stream go forever self.free = true; } Ok(Async::NotReady) => {} } } self.stream.poll() } } #[cfg(test)] mod tests { use super::*; use tokio::prelude::*; #[test] fn tokio_run() { use std::thread; let listener = tokio::net::TcpListener::bind(&"0.0.0.0:0".parse().unwrap()).unwrap(); let (exit, incoming) = Valved::new(listener.incoming()); let server = thread::spawn(move || { // start a tokio echo server tokio::run( incoming .map_err(|e| eprintln!("accept failed = {:?}", e)) .for_each(|sock| { let (reader, writer) = sock.split(); tokio::spawn( tokio::io::copy(reader, writer) .map(|amt| println!("wrote {:?} bytes", amt)) .map_err(|err| eprintln!("IO error {:?}", err)), ) }), ) }); // the server thread will normally never exit, since more connections // can always arrive. however, with a Valved, we can turn off the // stream of incoming connections to initiate a graceful shutdown exit.close(); server.join().unwrap(); } #[test] fn tokio_rt_on_idle() { let listener = tokio::net::TcpListener::bind(&"0.0.0.0:0".parse().unwrap()).unwrap(); let (exit, incoming) = Valved::new(listener.incoming()); let mut rt = tokio::runtime::Runtime::new().unwrap(); rt.spawn( incoming .map_err(|e| eprintln!("accept failed = {:?}", e)) .for_each(|sock| { let (reader, writer) = sock.split(); tokio::spawn( tokio::io::copy(reader, writer) .map(|amt| println!("wrote {:?} bytes", amt)) .map_err(|err| eprintln!("IO error {:?}", err)), ) }), ); exit.close(); rt.shutdown_on_idle().wait().unwrap(); } #[test] fn multi_interrupt() { let (exit, valve) = Valve::new(); let listener1 = tokio::net::TcpListener::bind(&"0.0.0.0:0".parse().unwrap()).unwrap(); let listener2 = tokio::net::TcpListener::bind(&"0.0.0.0:0".parse().unwrap()).unwrap(); let incoming1 = valve.wrap(listener1.incoming()); let incoming2 = valve.wrap(listener2.incoming()); let mut rt = tokio::runtime::Runtime::new().unwrap(); rt.spawn( incoming1 .select(incoming2) .map_err(|e| eprintln!("accept failed = {:?}", e)) .for_each(|sock| { let (reader, writer) = sock.split(); tokio::spawn( tokio::io::copy(reader, writer) .map(|amt| println!("wrote {:?} bytes", amt)) .map_err(|err| eprintln!("IO error {:?}", err)), ) }), ); // the runtime will not become idle until both incoming1 and incoming2 have stopped (due to // the select). this checks that they are indeed both interrupted when the valve is closed. exit.close(); rt.shutdown_on_idle().wait().unwrap(); } }