feat(katana-tasks): task manager

Cargo.toml

@@ -199,7 +199,7 @@ strum_macros = "0.25"
 tempfile = "3.9.0"
 test-log = "0.2.11"
 thiserror = "1.0.32"
-tokio = { version = "1.32.0", features = [ "full" ] }
+tokio = { version = "1.39.2", features = [ "full" ] }
 toml = "0.8"
 tower = "0.4.13"
 tower-http = "0.4.4"

crates/katana/tasks/Cargo.toml

@@ -10,3 +10,6 @@ futures.workspace = true
 rayon.workspace = true
 thiserror.workspace = true
 tokio.workspace = true
+tokio-metrics = "0.3.1"
+tokio-util = { version = "0.7.11", features = [ "rt" ] }
+tracing.workspace = true

crates/katana/tasks/src/lib.rs

@@ -1,3 +1,8 @@
+#![cfg_attr(not(test), warn(unused_crate_dependencies))]
+
+mod manager;
+mod task;
+
 use std::any::Any;
 use std::future::Future;
 use std::panic::{self, AssertUnwindSafe};
@@ -6,7 +11,9 @@ use std::sync::Arc;
 use std::task::Poll;
 
 use futures::channel::oneshot;
+pub use manager::*;
 use rayon::ThreadPoolBuilder;
+pub use task::*;
 use tokio::runtime::Handle;
 use tokio::task::JoinHandle;
 

crates/katana/tasks/src/manager.rs

@@ -0,0 +1,175 @@
+use std::future::Future;
+
+use tokio::runtime::Handle;
+use tokio::task::JoinHandle;
+use tokio_util::sync::CancellationToken;
+use tokio_util::task::TaskTracker;
+
+use crate::task::{TaskBuilder, TaskResult};
+
+pub type TaskHandle<T> = JoinHandle<TaskResult<T>>;
+
+/// Usage for this task manager is mainly to spawn tasks that can be cancelled, and captures
+/// panicked tasks (which in the context of the task manager - a critical task) for graceful
+/// shutdown.
+#[derive(Debug, Clone)]
+pub struct TaskManager {
+    /// A handle to the Tokio runtime.
+    handle: Handle,
+    /// Keep track of currently running tasks.
+    tracker: TaskTracker,
+    /// Used to cancel all running tasks.
+    ///
+    /// This is passed to all the tasks spawned by the manager.
+    pub(crate) on_cancel: CancellationToken,
+}
+
+impl TaskManager {
+    /// Create a new [`TaskManager`] from the given Tokio runtime handle.
+    pub fn new(handle: Handle) -> Self {
+        Self { handle, tracker: TaskTracker::new(), on_cancel: CancellationToken::new() }
+    }
+
+    pub fn current() -> Self {
+        Self::new(Handle::current())
+    }
+
+    pub fn spawn<F>(&self, fut: F) -> TaskHandle<F::Output>
+    where
+        F: Future + Send + 'static,
+        F::Output: Send + 'static,
+    {
+        self.spawn_inner(fut)
+    }
+
+    /// Wait until all spawned tasks are completed.
+    pub async fn wait(&self) {
+        // need to close the tracker first before waiting
+        let _ = self.tracker.close();
+        self.tracker.wait().await;
+        // reopen the tracker for spawning future tasks
+        let _ = self.tracker.reopen();
+    }
+
+    /// Consumes the manager and wait until all tasks are finished, either due to completion or
+    /// cancellation.
+    pub async fn wait_shutdown(self) {
+        // need to close the tracker first before waiting
+        let _ = self.tracker.close();
+        let _ = self.on_cancel.cancelled().await;
+        self.tracker.wait().await;
+    }
+
+    /// Return the handle to the Tokio runtime that the manager is associated with.
+    pub fn handle(&self) -> &Handle {
+        &self.handle
+    }
+
+    /// Returns a new [`TaskBuilder`] for building a task to be spawned on this manager.
+    pub fn build_task(&self) -> TaskBuilder<'_> {
+        TaskBuilder::new(self)
+    }
+
+    fn spawn_inner<F>(&self, task: F) -> TaskHandle<F::Output>
+    where
+        F: Future + Send + 'static,
+        F::Output: Send + 'static,
+    {
+        let task = self.make_cancellable(task);
+        let task = self.tracker.track_future(task);
+        self.handle.spawn(task)
+    }
+
+    fn make_cancellable<F>(&self, fut: F) -> impl Future<Output = TaskResult<F::Output>>
+    where
+        F: Future,
+    {
+        let ct = self.on_cancel.clone();
+        async move {
+            tokio::select! {
+                _ = ct.cancelled() => {
+                    TaskResult::Cancelled
+                },
+                res = fut => {
+                    TaskResult::Completed(res)
+                },
+            }
+        }
+    }
+}
+
+impl Drop for TaskManager {
+    fn drop(&mut self) {
+        self.on_cancel.cancel();
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use futures::future;
+    use tokio::time::{self, Duration};
+
+    use super::*;
+
+    #[tokio::test]
+    async fn normal_tasks() {
+        let manager = TaskManager::current();
+
+        manager.spawn(time::sleep(Duration::from_secs(1)));
+        manager.spawn(time::sleep(Duration::from_secs(1)));
+        manager.spawn(time::sleep(Duration::from_secs(1)));
+
+        // 3 tasks should be spawned on the manager
+        assert_eq!(manager.tracker.len(), 3);
+
+        // wait until all task spawned to the manager have been completed
+        manager.wait().await;
+
+        assert!(
+            !manager.on_cancel.is_cancelled(),
+            "cancellation signal shouldn't be sent on normal task completion"
+        )
+    }
+
+    #[tokio::test]
+    async fn task_with_graceful_shutdown() {
+        let manager = TaskManager::current();
+
+        // mock long running normal task and a task with graceful shutdown
+        manager.build_task().spawn(async {
+            loop {
+                time::sleep(Duration::from_secs(1)).await
+            }
+        });
+
+        manager.build_task().spawn(async {
+            loop {
+                time::sleep(Duration::from_secs(1)).await
+            }
+        });
+
+        // assert that 2 tasks should've been spawned
+        assert_eq!(manager.tracker.len(), 2);
+
+        // Spawn a task with graceful shuwdown that finish immediately.
+        // The long running task should be cancelled due to the graceful shutdown.
+        manager.build_task().graceful_shutdown().spawn(future::ready(()));
+
+        // wait until all task spawned to the manager have been completed
+        manager.wait_shutdown().await;
+    }
+
+    #[tokio::test]
+    async fn critical_task_implicit_graceful_shutdown() {
+        let manager = TaskManager::current();
+        manager.build_task().critical().spawn(future::ready(()));
+        manager.wait_shutdown().await;
+    }
+
+    #[tokio::test]
+    async fn critical_task_graceful_shudown_on_panicked() {
+        let manager = TaskManager::current();
+        manager.build_task().critical().spawn(async { panic!("panicking") });
+        manager.wait_shutdown().await;
+    }
+}