await-tree 0.3.1

Generate accurate and informative tree dumps of asynchronous tasks.
Documentation 
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// Copyright 2023 RisingWave Labs
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// TODO: should we consider exposing `current_registry`
// so that users can not only spawn tasks but also get and collect trees?

use std::future::Future;

use tokio::task::JoinHandle;

use crate::{Key, Registry, Span, ToRootSpan};

impl Registry {
    /// Spawns a new asynchronous task instrumented with the given root [`Span`], returning a
    /// [`JoinHandle`] for it.
    ///
    /// The spawned task will be registered in the this registry.
    pub fn spawn<T>(
        &self,
        key: impl Key,
        root_span: impl Into<Span>,
        future: T,
    ) -> JoinHandle<T::Output>
    where
        T: Future + Send + 'static,
        T::Output: Send + 'static,
    {
        tokio::spawn(self.register(key, root_span).instrument(future))
    }

    /// Spawns a new asynchronous task instrumented with the root span derived from the given key,
    /// returning a [`JoinHandle`] for it.
    ///
    /// The spawned task will be registered in the this registry.
    ///
    /// This is a convenience method for `self.spawn(key, key.to_root_span(), future)`.
    pub fn spawn_derived_root<T>(
        &self,
        key: impl Key + ToRootSpan,
        future: T,
    ) -> JoinHandle<T::Output>
    where
        T: Future + Send + 'static,
        T::Output: Send + 'static,
    {
        let root_span = key.to_root_span();
        self.spawn(key, root_span, future)
    }

    /// Spawns a new asynchronous task instrumented with the given root [`Span`], returning a
    /// [`JoinHandle`] for it.
    ///
    /// The spawned task will be registered in the this registry anonymously.
    pub fn spawn_anonymous<T>(&self, root_span: impl Into<Span>, future: T) -> JoinHandle<T::Output>
    where
        T: Future + Send + 'static,
        T::Output: Send + 'static,
    {
        tokio::spawn(self.register_anonymous(root_span).instrument(future))
    }
}

/// Spawns a new asynchronous task instrumented with the given root [`Span`], returning a
/// [`JoinHandle`] for it.
///
/// The spawned task will be registered in the current [`Registry`](crate::Registry) returned by
/// [`Registry::try_current`] with the given [`Key`], if it exists. Otherwise, this is equivalent to
/// [`tokio::spawn`].
pub fn spawn<T>(key: impl Key, root_span: impl Into<Span>, future: T) -> JoinHandle<T::Output>
where
    T: Future + Send + 'static,
    T::Output: Send + 'static,
{
    if let Some(registry) = Registry::try_current() {
        registry.spawn(key, root_span, future)
    } else {
        tokio::spawn(future)
    }
}

/// Spawns a new asynchronous task instrumented with the root span derived from the given key,
/// returning a [`JoinHandle`] for it.
///
/// The spawned task will be registered in the current [`Registry`](crate::Registry) returned by
/// [`Registry::try_current`] with the given [`Key`], if it exists. Otherwise, this is equivalent to
/// [`tokio::spawn`].
///
/// This is a convenience function for `spawn(key, key.to_root_span(), future)`. See [`spawn`] for
/// more details.
pub fn spawn_derived_root<T>(key: impl Key + ToRootSpan, future: T) -> JoinHandle<T::Output>
where
    T: Future + Send + 'static,
    T::Output: Send + 'static,
{
    let root_span = key.to_root_span();
    spawn(key, root_span, future)
}

/// Spawns a new asynchronous task instrumented with the given root [`Span`], returning a
/// [`JoinHandle`] for it.
///
/// The spawned task will be registered in the current [`Registry`](crate::Registry) returned by
/// [`Registry::try_current`] anonymously, if it exists. Otherwise, this is equivalent to
/// [`tokio::spawn`].
pub fn spawn_anonymous<T>(root_span: impl Into<Span>, future: T) -> JoinHandle<T::Output>
where
    T: Future + Send + 'static,
    T::Output: Send + 'static,
{
    if let Some(registry) = Registry::try_current() {
        registry.spawn_anonymous(root_span, future)
    } else {
        tokio::spawn(future)
    }
}