cancel on drop

src/common/runtime/src/lib.rs

@@ -10,7 +10,7 @@ use std::{
 use common_error::{DaftError, DaftResult};
 use futures::FutureExt;
 use lazy_static::lazy_static;
-use tokio::{runtime::RuntimeFlavor, task::JoinHandle};
+use tokio::{runtime::RuntimeFlavor, task::JoinError};
 
 lazy_static! {
     static ref NUM_CPUS: usize = std::thread::available_parallelism().unwrap().get();
@@ -41,7 +41,6 @@ impl Runtime {
         Arc::new(Self { runtime, pool_type })
     }
 
-    // TODO: figure out a way to cancel the Future if this output is dropped.
     async fn execute_task<F>(future: F, pool_type: PoolType) -> DaftResult<F::Output>
     where
         F: Future + Send + 'static,
@@ -81,36 +80,25 @@ impl Runtime {
         rx.recv().expect("Spawned task transmitter dropped")
     }
 
-    /// Spawn a task on the runtime and await on it.
-    /// You should use this when you are spawning compute or IO tasks from the Executor.
-    pub async fn await_on<F>(&self, future: F) -> DaftResult<F::Output>
-    where
-        F: Future + Send + 'static,
-        F::Output: Send + 'static,
-    {
-        let (tx, rx) = oneshot::channel();
-        let pool_type = self.pool_type;
-        let _join_handle = self.spawn(async move {
-            let task_output = Self::execute_task(future, pool_type).await;
-            if tx.send(task_output).is_err() {
-                log::warn!("Spawned task output ignored: receiver dropped");
-            }
-        });
-        rx.await.expect("Spawned task transmitter dropped")
-    }
-
     /// Blocks current thread to compute future. Can not be called in tokio runtime context
     ///
     pub fn block_on_current_thread<F: Future>(&self, future: F) -> F::Output {
         self.runtime.block_on(future)
     }
 
-    pub fn spawn<F>(&self, future: F) -> JoinHandle<F::Output>
+    // Spawn a task on the runtime
+    pub fn spawn<F>(
+        &self,
+        future: F,
+    ) -> impl Future<Output = Result<F::Output, JoinError>> + Send + 'static
     where
         F: Future + Send + 'static,
         F::Output: Send + 'static,
     {
-        self.runtime.spawn(future)
+        // Spawn it on a joinset on the runtime, such that if the future gets dropped, the task is cancelled
+        let mut joinset = tokio::task::JoinSet::new();
+        joinset.spawn_on(future, self.runtime.handle());
+        async move { joinset.join_next().await.expect("just spawned task") }.boxed()
     }
 }
 
@@ -183,3 +171,34 @@ pub fn get_io_pool_num_threads() -> Option<usize> {
         Err(_) => None,
     }
 }
+
+mod tests {
+
+    #[tokio::test]
+    async fn test_spawned_task_cancelled_when_dropped() {
+        use super::*;
+
+        let runtime = get_compute_runtime();
+        let ptr = Arc::new(AtomicUsize::new(0));
+        let ptr_clone = ptr.clone();
+
+        // Spawn a task that just does work in a loop
+        // The task should own a reference to the Arc, so the strong count should be 2
+        let task = async move {
+            loop {
+                tokio::time::sleep(std::time::Duration::from_secs(1)).await;
+                ptr_clone.fetch_add(1, Ordering::SeqCst);
+            }
+        };
+        let fut = runtime.spawn(task);
+        assert!(Arc::strong_count(&ptr) == 2);
+
+        // Drop the future, which should cancel the task
+        drop(fut);
+
+        // Wait for a while so that the task can be aborted
+        tokio::time::sleep(std::time::Duration::from_secs(2)).await;
+        // The strong count should be 1 now
+        assert!(Arc::strong_count(&ptr) == 1);
+    }
+}

src/daft-local-execution/src/intermediate_ops/intermediate_op.rs

@@ -4,14 +4,15 @@ use common_display::tree::TreeDisplay;
 use common_error::DaftResult;
 use common_runtime::get_compute_runtime;
 use daft_micropartition::MicroPartition;
+use snafu::ResultExt;
 use tracing::{info_span, instrument};
 
 use super::buffer::OperatorBuffer;
 use crate::{
     channel::{create_channel, PipelineChannel, Receiver, Sender},
     pipeline::{PipelineNode, PipelineResultType},
     runtime_stats::{CountingReceiver, CountingSender, RuntimeStatsContext},
-    ExecutionRuntimeHandle, NUM_CPUS,
+    ExecutionRuntimeHandle, JoinSnafu, NUM_CPUS,
 };
 
 pub(crate) trait DynIntermediateOpState: Send + Sync {
@@ -119,7 +120,7 @@ impl IntermediateNode {
                 let fut = async move {
                     rt_context.in_span(&span, || op.execute(idx, &morsel, &state_wrapper))
                 };
-                let result = compute_runtime.await_on(fut).await??;
+                let result = compute_runtime.spawn(fut).await.context(JoinSnafu)??;
                 match result {
                     IntermediateOperatorResult::NeedMoreInput(Some(mp)) => {
                         let _ = sender.send(mp.into()).await;

src/daft-local-execution/src/sinks/blocking_sink.rs

@@ -4,13 +4,14 @@ use common_display::tree::TreeDisplay;
 use common_error::DaftResult;
 use common_runtime::get_compute_runtime;
 use daft_micropartition::MicroPartition;
+use snafu::ResultExt;
 use tracing::info_span;
 
 use crate::{
     channel::PipelineChannel,
     pipeline::{PipelineNode, PipelineResultType},
     runtime_stats::RuntimeStatsContext,
-    ExecutionRuntimeHandle,
+    ExecutionRuntimeHandle, JoinSnafu,
 };
 pub enum BlockingSinkStatus {
     NeedMoreInput,
@@ -102,19 +103,20 @@ impl PipelineNode for BlockingSinkNode {
                         let mut guard = op.lock().await;
                         rt_context.in_span(&span, || guard.sink(val.as_data()))
                     };
-                    let result = compute_runtime.await_on(fut).await??;
+                    let result = compute_runtime.spawn(fut).await.context(JoinSnafu)??;
                     if matches!(result, BlockingSinkStatus::Finished) {
                         break;
                     }
                 }
                 let finalized_result = compute_runtime
-                    .await_on(async move {
+                    .spawn(async move {
                         let mut guard = op.lock().await;
                         rt_context.in_span(&info_span!("BlockingSinkNode::finalize"), || {
                             guard.finalize()
                         })
                     })
-                    .await??;
+                    .await
+                    .context(JoinSnafu)??;
                 if let Some(part) = finalized_result {
                     let _ = destination_sender.send(part).await;
                 }

src/daft-local-execution/src/sinks/streaming_sink.rs

@@ -125,7 +125,7 @@ impl StreamingSinkNode {
                 let fut = async move {
                     rt_context.in_span(&span, || op.execute(idx, &morsel, state_wrapper.as_ref()))
                 };
-                let result = compute_runtime.await_on(fut).await??;
+                let result = compute_runtime.spawn(fut).await.context(JoinSnafu)??;
                 match result {
                     StreamingSinkOutput::NeedMoreInput(mp) => {
                         if let Some(mp) = mp {
@@ -281,12 +281,13 @@ impl PipelineNode for StreamingSinkNode {
 
                 let compute_runtime = get_compute_runtime();
                 let finalized_result = compute_runtime
-                    .await_on(async move {
+                    .spawn(async move {
                         runtime_stats.in_span(&info_span!("StreamingSinkNode::finalize"), || {
                             op.finalize(finished_states)
                         })
                     })
-                    .await??;
+                    .await
+                    .context(JoinSnafu)??;
                 if let Some(res) = finalized_result {
                     let _ = destination_sender.send(res.into()).await;
                 }

src/daft-local-execution/src/sources/scan_task.rs

@@ -139,7 +139,7 @@ async fn get_delete_map(
         .get_io_client_and_runtime()?;
     let scan_tasks = scan_tasks.to_vec();
     runtime
-        .await_on(async move {
+        .spawn(async move {
             let mut delete_map = scan_tasks
                 .iter()
                 .flat_map(|st| st.sources.iter().map(|s| s.get_path().to_string()))
@@ -183,7 +183,8 @@ async fn get_delete_map(
             }
             Ok(Some(delete_map))
         })
-        .await?
+        .await
+        .context(JoinSnafu)?
 }
 
 async fn stream_scan_task(