| use crate::runtime::blocking::{BlockingTask, NoopSchedule}; |
| use crate::runtime::task::{self, JoinHandle}; |
| use crate::runtime::{blocking, context, driver, Spawner}; |
| use crate::util::error::CONTEXT_MISSING_ERROR; |
| |
| use std::future::Future; |
| use std::{error, fmt}; |
| |
| /// Handle to the runtime. |
| /// |
| /// The handle is internally reference-counted and can be freely cloned. A handle can be |
| /// obtained using the [`Runtime::handle`] method. |
| /// |
| /// [`Runtime::handle`]: crate::runtime::Runtime::handle() |
| #[derive(Debug, Clone)] |
| pub struct Handle { |
| pub(super) spawner: Spawner, |
| |
| /// Handles to the I/O drivers |
| pub(super) io_handle: driver::IoHandle, |
| |
| /// Handles to the signal drivers |
| pub(super) signal_handle: driver::SignalHandle, |
| |
| /// Handles to the time drivers |
| pub(super) time_handle: driver::TimeHandle, |
| |
| /// Source of `Instant::now()` |
| pub(super) clock: driver::Clock, |
| |
| /// Blocking pool spawner |
| pub(super) blocking_spawner: blocking::Spawner, |
| } |
| |
| /// Runtime context guard. |
| /// |
| /// Returned by [`Runtime::enter`] and [`Handle::enter`], the context guard exits |
| /// the runtime context on drop. |
| /// |
| /// [`Runtime::enter`]: fn@crate::runtime::Runtime::enter |
| #[derive(Debug)] |
| #[must_use = "Creating and dropping a guard does nothing"] |
| pub struct EnterGuard<'a> { |
| handle: &'a Handle, |
| guard: context::EnterGuard, |
| } |
| |
| impl Handle { |
| /// Enter the runtime context. This allows you to construct types that must |
| /// have an executor available on creation such as [`Sleep`] or [`TcpStream`]. |
| /// It will also allow you to call methods such as [`tokio::spawn`]. |
| /// |
| /// [`Sleep`]: struct@crate::time::Sleep |
| /// [`TcpStream`]: struct@crate::net::TcpStream |
| /// [`tokio::spawn`]: fn@crate::spawn |
| pub fn enter(&self) -> EnterGuard<'_> { |
| EnterGuard { |
| handle: self, |
| guard: context::enter(self.clone()), |
| } |
| } |
| |
| /// Returns a `Handle` view over the currently running `Runtime` |
| /// |
| /// # Panic |
| /// |
| /// This will panic if called outside the context of a Tokio runtime. That means that you must |
| /// call this on one of the threads **being run by the runtime**. Calling this from within a |
| /// thread created by `std::thread::spawn` (for example) will cause a panic. |
| /// |
| /// # Examples |
| /// |
| /// This can be used to obtain the handle of the surrounding runtime from an async |
| /// block or function running on that runtime. |
| /// |
| /// ``` |
| /// # use std::thread; |
| /// # use tokio::runtime::Runtime; |
| /// # fn dox() { |
| /// # let rt = Runtime::new().unwrap(); |
| /// # rt.spawn(async { |
| /// use tokio::runtime::Handle; |
| /// |
| /// // Inside an async block or function. |
| /// let handle = Handle::current(); |
| /// handle.spawn(async { |
| /// println!("now running in the existing Runtime"); |
| /// }); |
| /// |
| /// # let handle = |
| /// thread::spawn(move || { |
| /// // Notice that the handle is created outside of this thread and then moved in |
| /// handle.spawn(async { /* ... */ }) |
| /// // This next line would cause a panic |
| /// // let handle2 = Handle::current(); |
| /// }); |
| /// # handle.join().unwrap(); |
| /// # }); |
| /// # } |
| /// ``` |
| pub fn current() -> Self { |
| context::current().expect(CONTEXT_MISSING_ERROR) |
| } |
| |
| /// Returns a Handle view over the currently running Runtime |
| /// |
| /// Returns an error if no Runtime has been started |
| /// |
| /// Contrary to `current`, this never panics |
| pub fn try_current() -> Result<Self, TryCurrentError> { |
| context::current().ok_or(TryCurrentError(())) |
| } |
| |
| /// Spawn a future onto the Tokio runtime. |
| /// |
| /// This spawns the given future onto the runtime's executor, usually a |
| /// thread pool. The thread pool is then responsible for polling the future |
| /// until it completes. |
| /// |
| /// See [module level][mod] documentation for more details. |
| /// |
| /// [mod]: index.html |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use tokio::runtime::Runtime; |
| /// |
| /// # fn dox() { |
| /// // Create the runtime |
| /// let rt = Runtime::new().unwrap(); |
| /// // Get a handle from this runtime |
| /// let handle = rt.handle(); |
| /// |
| /// // Spawn a future onto the runtime using the handle |
| /// handle.spawn(async { |
| /// println!("now running on a worker thread"); |
| /// }); |
| /// # } |
| /// ``` |
| #[cfg_attr(tokio_track_caller, track_caller)] |
| pub fn spawn<F>(&self, future: F) -> JoinHandle<F::Output> |
| where |
| F: Future + Send + 'static, |
| F::Output: Send + 'static, |
| { |
| #[cfg(all(tokio_unstable, feature = "tracing"))] |
| let future = crate::util::trace::task(future, "task", None); |
| self.spawner.spawn(future) |
| } |
| |
| /// Run the provided function on an executor dedicated to blocking |
| /// operations. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use tokio::runtime::Runtime; |
| /// |
| /// # fn dox() { |
| /// // Create the runtime |
| /// let rt = Runtime::new().unwrap(); |
| /// // Get a handle from this runtime |
| /// let handle = rt.handle(); |
| /// |
| /// // Spawn a blocking function onto the runtime using the handle |
| /// handle.spawn_blocking(|| { |
| /// println!("now running on a worker thread"); |
| /// }); |
| /// # } |
| #[cfg_attr(tokio_track_caller, track_caller)] |
| pub fn spawn_blocking<F, R>(&self, func: F) -> JoinHandle<R> |
| where |
| F: FnOnce() -> R + Send + 'static, |
| R: Send + 'static, |
| { |
| self.spawn_blocking_inner(func, None) |
| } |
| |
| #[cfg_attr(tokio_track_caller, track_caller)] |
| pub(crate) fn spawn_blocking_inner<F, R>(&self, func: F, name: Option<&str>) -> JoinHandle<R> |
| where |
| F: FnOnce() -> R + Send + 'static, |
| R: Send + 'static, |
| { |
| let fut = BlockingTask::new(func); |
| |
| #[cfg(all(tokio_unstable, feature = "tracing"))] |
| let fut = { |
| use tracing::Instrument; |
| #[cfg(tokio_track_caller)] |
| let location = std::panic::Location::caller(); |
| #[cfg(tokio_track_caller)] |
| let span = tracing::trace_span!( |
| target: "tokio::task", |
| "task", |
| kind = %"blocking", |
| function = %std::any::type_name::<F>(), |
| task.name = %name.unwrap_or_default(), |
| spawn.location = %format_args!("{}:{}:{}", location.file(), location.line(), location.column()), |
| ); |
| #[cfg(not(tokio_track_caller))] |
| let span = tracing::trace_span!( |
| target: "tokio::task", |
| "task", |
| kind = %"blocking", |
| task.name = %name.unwrap_or_default(), |
| function = %std::any::type_name::<F>(), |
| ); |
| fut.instrument(span) |
| }; |
| |
| #[cfg(not(all(tokio_unstable, feature = "tracing")))] |
| let _ = name; |
| |
| let (task, handle) = task::unowned(fut, NoopSchedule); |
| let _ = self.blocking_spawner.spawn(task, self); |
| handle |
| } |
| |
| /// Run a future to completion on this `Handle`'s associated `Runtime`. |
| /// |
| /// This runs the given future on the current thread, blocking until it is |
| /// complete, and yielding its resolved result. Any tasks or timers which |
| /// the future spawns internally will be executed on the runtime. |
| /// |
| /// When this is used on a `current_thread` runtime, only the |
| /// [`Runtime::block_on`] method can drive the IO and timer drivers, but the |
| /// `Handle::block_on` method cannot drive them. This means that, when using |
| /// this method on a current_thread runtime, anything that relies on IO or |
| /// timers will not work unless there is another thread currently calling |
| /// [`Runtime::block_on`] on the same runtime. |
| /// |
| /// # If the runtime has been shut down |
| /// |
| /// If the `Handle`'s associated `Runtime` has been shut down (through |
| /// [`Runtime::shutdown_background`], [`Runtime::shutdown_timeout`], or by |
| /// dropping it) and `Handle::block_on` is used it might return an error or |
| /// panic. Specifically IO resources will return an error and timers will |
| /// panic. Runtime independent futures will run as normal. |
| /// |
| /// # Panics |
| /// |
| /// This function panics if the provided future panics, if called within an |
| /// asynchronous execution context, or if a timer future is executed on a |
| /// runtime that has been shut down. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use tokio::runtime::Runtime; |
| /// |
| /// // Create the runtime |
| /// let rt = Runtime::new().unwrap(); |
| /// |
| /// // Get a handle from this runtime |
| /// let handle = rt.handle(); |
| /// |
| /// // Execute the future, blocking the current thread until completion |
| /// handle.block_on(async { |
| /// println!("hello"); |
| /// }); |
| /// ``` |
| /// |
| /// Or using `Handle::current`: |
| /// |
| /// ``` |
| /// use tokio::runtime::Handle; |
| /// |
| /// #[tokio::main] |
| /// async fn main () { |
| /// let handle = Handle::current(); |
| /// std::thread::spawn(move || { |
| /// // Using Handle::block_on to run async code in the new thread. |
| /// handle.block_on(async { |
| /// println!("hello"); |
| /// }); |
| /// }); |
| /// } |
| /// ``` |
| /// |
| /// [`JoinError`]: struct@crate::task::JoinError |
| /// [`JoinHandle`]: struct@crate::task::JoinHandle |
| /// [`Runtime::block_on`]: fn@crate::runtime::Runtime::block_on |
| /// [`Runtime::shutdown_background`]: fn@crate::runtime::Runtime::shutdown_background |
| /// [`Runtime::shutdown_timeout`]: fn@crate::runtime::Runtime::shutdown_timeout |
| /// [`spawn_blocking`]: crate::task::spawn_blocking |
| /// [`tokio::fs`]: crate::fs |
| /// [`tokio::net`]: crate::net |
| /// [`tokio::time`]: crate::time |
| pub fn block_on<F: Future>(&self, future: F) -> F::Output { |
| // Enter the **runtime** context. This configures spawning, the current I/O driver, ... |
| let _rt_enter = self.enter(); |
| |
| // Enter a **blocking** context. This prevents blocking from a runtime. |
| let mut blocking_enter = crate::runtime::enter(true); |
| |
| // Block on the future |
| blocking_enter |
| .block_on(future) |
| .expect("failed to park thread") |
| } |
| |
| pub(crate) fn shutdown(mut self) { |
| self.spawner.shutdown(); |
| } |
| } |
| |
| /// Error returned by `try_current` when no Runtime has been started |
| pub struct TryCurrentError(()); |
| |
| impl fmt::Debug for TryCurrentError { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| f.debug_struct("TryCurrentError").finish() |
| } |
| } |
| |
| impl fmt::Display for TryCurrentError { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| f.write_str(CONTEXT_MISSING_ERROR) |
| } |
| } |
| |
| impl error::Error for TryCurrentError {} |