fix(streaming): drop subtask on another blocking thread (#8672)

Signed-off-by: Bugen Zhao <i@bugenzhao.com>

src/compute/src/rpc/service/stream_service.rs

@@ -108,7 +108,7 @@ impl StreamService for StreamServiceImpl {
     ) -> std::result::Result<Response<DropActorsResponse>, Status> {
         let req = request.into_inner();
         let actors = req.actor_ids;
-        self.mgr.drop_actor(&actors).await?;
+        self.mgr.drop_actors(&actors).await?;
         Ok(Response::new(DropActorsResponse {
             request_id: req.request_id,
             status: None,

src/stream/src/executor/subtask.rs

@@ -19,7 +19,8 @@ use tokio::sync::mpsc::error::SendError;
 use tokio_stream::wrappers::ReceiverStream;
 
 use super::actor::spawn_blocking_drop_stream;
-use super::{BoxedExecutor, Executor, ExecutorInfo, MessageStreamItem};
+use super::{BoxedExecutor, Executor, ExecutorInfo, Message, MessageStreamItem};
+use crate::task::ActorId;
 
 /// Handle used to drive the subtask.
 pub type SubtaskHandle = impl Future<Output = ()> + Send + 'static;
@@ -60,7 +61,7 @@ impl Executor for SubtaskRxExecutor {
 /// Used when there're multiple stateful executors in an actor. These subtasks can be concurrently
 /// executed to improve the I/O performance, while the computing resource can be still bounded to a
 /// single thread.
-pub fn wrap(input: BoxedExecutor) -> (SubtaskHandle, SubtaskRxExecutor) {
+pub fn wrap(input: BoxedExecutor, actor_id: ActorId) -> (SubtaskHandle, SubtaskRxExecutor) {
     let (tx, rx) = mpsc::channel(1);
     let rx_executor = SubtaskRxExecutor {
         info: ExecutorInfo {
@@ -72,7 +73,18 @@ pub fn wrap(input: BoxedExecutor) -> (SubtaskHandle, SubtaskRxExecutor) {
 
     let handle = async move {
         let mut input = input.execute();
+
         while let Some(item) = input.next().await {
+            // Decide whether to stop the subtask. We explicitly do this instead of relying on the
+            // termination of the input stream, because we don't want to exhaust the stream, which
+            // causes the stream dropped in the scope of the current async task and blocks other
+            // actors. See `spawn_blocking_drop_stream` for more details.
+            let to_stop = match &item {
+                Ok(Message::Barrier(barrier)) => barrier.is_stop_or_update_drop_actor(actor_id),
+                Ok(_) => false,
+                Err(_) => true,
+            };
+
             // It's possible that the downstream itself yields an error (e.g. from remote input) and
             // finishes, so we may fail to send the message. In this case, we can simply ignore the
             // send error and exit as well. If the message itself is another error, log it.
@@ -85,7 +97,12 @@ pub fn wrap(input: BoxedExecutor) -> (SubtaskHandle, SubtaskRxExecutor) {
                 }
                 break;
             }
+
+            if to_stop {
+                break;
+            }
         }
+
         spawn_blocking_drop_stream(input).await;
     }
     .instrument_await("Subtask");

src/stream/src/task/stream_manager.rs

@@ -310,18 +310,19 @@ impl LocalStreamManager {
         Ok(())
     }
 
-    pub async fn drop_actor(&self, actors: &[ActorId]) -> StreamResult<()> {
+    /// Drop the resources of the given actors.
+    pub async fn drop_actors(&self, actors: &[ActorId]) -> StreamResult<()> {
         let mut core = self.core.lock().await;
-        for id in actors {
-            core.drop_actor(*id);
+        for &id in actors {
+            core.drop_actor(id);
         }
         tracing::debug!(actors = ?actors, "drop actors");
         Ok(())
     }
 
-    /// Force stop all actors on this worker.
+    /// Force stop all actors on this worker, and then drop their resources.
     pub async fn stop_all_actors(&self) -> StreamResult<()> {
-        self.core.lock().await.drop_all_actors().await;
+        self.core.lock().await.stop_all_actors().await;
         // Clear shared buffer in storage to release memory
         self.clear_storage_buffer().await;
         self.clear_all_senders_and_collect_rx();
@@ -557,7 +558,7 @@ impl LocalStreamManagerCore {
 
         // If there're multiple stateful executors in this actor, we will wrap it into a subtask.
         let executor = if has_stateful && is_stateful {
-            let (subtask, executor) = subtask::wrap(executor);
+            let (subtask, executor) = subtask::wrap(executor, actor_context.id);
             subtasks.push(subtask);
             executor.boxed()
         } else {
@@ -781,14 +782,16 @@ impl LocalStreamManagerCore {
             .inspect(|handle| handle.abort());
         self.context.actor_infos.write().remove(&actor_id);
         self.actors.remove(&actor_id);
-        // Task should have already stopped when this method is invoked.
-        self.handles
-            .remove(&actor_id)
-            .inspect(|handle| handle.abort());
+
+        // Task should have already stopped when this method is invoked. There might be some
+        // clean-up work left (like dropping in-memory data structures), but we don't have to wait
+        // for them to finish, in order to make this request non-blocking.
+        self.handles.remove(&actor_id);
     }
 
-    /// `drop_all_actors` is invoked by meta node via RPC for recovery purpose.
-    async fn drop_all_actors(&mut self) {
+    /// `stop_all_actors` is invoked by meta node via RPC for recovery purpose. Different from the
+    /// `drop_actor`, the execution of the actors will be aborted.
+    async fn stop_all_actors(&mut self) {
         for (actor_id, handle) in &self.handles {
             tracing::debug!("force stopping actor {}", actor_id);
             handle.abort();