refactor: wal pipeline will exit task on drop

Signed-off-by: bsbds <69835502+bsbds@users.noreply.github.com>

crates/curp/src/server/storage/wal/pipeline.rs

@@ -6,6 +6,7 @@ use std::{
         Arc,
     },
     task::Poll,
+    thread::JoinHandle,
 };
 
 use clippy_utilities::OverflowArithmetic;
@@ -28,14 +29,16 @@ pub(super) struct FilePipeline {
     ///
     /// As tokio::fs is generally slower than std::fs, we use synchronous file allocation.
     /// Please also refer to the issue discussed on the tokio repo: https://github.com/tokio-rs/tokio/issues/3664
-    file_iter: flume::IntoIter<LockedFile>,
+    file_iter: Option<flume::IntoIter<LockedFile>>,
     /// Stopped flag
     stopped: Arc<AtomicBool>,
+    /// Join handle of the allocation task
+    file_alloc_task_handle: Option<JoinHandle<()>>,
 }
 
 impl FilePipeline {
     /// Creates a new `FilePipeline`
-    pub(super) fn new(dir: PathBuf, file_size: u64) -> io::Result<Self> {
+    pub(super) fn new(dir: PathBuf, file_size: u64) -> Self {
         if let Err(e) = Self::clean_up(&dir) {
             error!("Failed to clean up tmp files: {e}");
         }
@@ -46,61 +49,74 @@ impl FilePipeline {
         let stopped_c = Arc::clone(&stopped);
 
         #[cfg(not(madsim))]
-        let _ignore = std::thread::spawn(move || {
-            let mut file_count = 0;
-            loop {
-                match Self::alloc(&dir_c, file_size, &mut file_count) {
-                    Ok(file) => {
-                        if file_tx.send(file).is_err() {
-                            // The receiver is already dropped, stop this task
-                            break;
-                        }
-                        if stopped_c.load(Ordering::Relaxed) {
-                            if let Err(e) = Self::clean_up(&dir_c) {
-                                error!("failed to clean up pipeline temp files: {e}");
+        {
+            let file_alloc_task_handle = std::thread::spawn(move || {
+                let mut file_count = 0;
+                loop {
+                    match Self::alloc(&dir_c, file_size, &mut file_count) {
+                        Ok(file) => {
+                            if file_tx.send(file).is_err() {
+                                // The receiver is already dropped, stop this task
+                                break;
                             }
+                            if stopped_c.load(Ordering::Relaxed) {
+                                if let Err(e) = Self::clean_up(&dir_c) {
+                                    error!("failed to clean up pipeline temp files: {e}");
+                                }
+                                break;
+                            }
+                        }
+                        Err(e) => {
+                            error!("failed to allocate file: {e}");
                             break;
                         }
                     }
-                    Err(e) => {
-                        error!("failed to allocate file: {e}");
-                        break;
-                    }
                 }
+            });
+
+            Self {
+                dir,
+                file_size,
+                file_iter: Some(file_rx.into_iter()),
+                stopped,
+                file_alloc_task_handle: Some(file_alloc_task_handle),
             }
-        });
+        }
 
         #[cfg(madsim)]
-        let _ignore = tokio::spawn(async move {
-            let mut file_count = 0;
-            loop {
-                match Self::alloc(&dir_c, file_size, &mut file_count) {
-                    Ok(file) => {
-                        if file_tx.send_async(file).await.is_err() {
-                            // The receiver is already dropped, stop this task
-                            break;
-                        }
-                        if stopped_c.load(Ordering::Relaxed) {
-                            if let Err(e) = Self::clean_up(&dir_c) {
-                                error!("failed to clean up pipeline temp files: {e}");
+        {
+            let _ignore = tokio::spawn(async move {
+                let mut file_count = 0;
+                loop {
+                    match Self::alloc(&dir_c, file_size, &mut file_count) {
+                        Ok(file) => {
+                            if file_tx.send_async(file).await.is_err() {
+                                // The receiver is already dropped, stop this task
+                                break;
+                            }
+                            if stopped_c.load(Ordering::Relaxed) {
+                                if let Err(e) = Self::clean_up(&dir_c) {
+                                    error!("failed to clean up pipeline temp files: {e}");
+                                }
+                                break;
                             }
+                        }
+                        Err(e) => {
+                            error!("failed to allocate file: {e}");
                             break;
                         }
                     }
-                    Err(e) => {
-                        error!("failed to allocate file: {e}");
-                        break;
-                    }
                 }
+            });
+
+            Self {
+                dir,
+                file_size,
+                file_iter: Some(file_rx.into_iter()),
+                stopped,
+                file_alloc_task_handle: None,
             }
-        });
-
-        Ok(Self {
-            dir,
-            file_size,
-            file_iter: file_rx.into_iter(),
-            stopped,
-        })
+        }
     }
 
     /// Stops the pipeline
@@ -134,6 +150,11 @@ impl FilePipeline {
 impl Drop for FilePipeline {
     fn drop(&mut self) {
         self.stop();
+        // Drops the file rx so that the allocation task could exit
+        drop(self.file_iter.take());
+        if let Some(Err(e)) = self.file_alloc_task_handle.take().map(JoinHandle::join) {
+            error!("failed to join file allocation task: {e:?}");
+        }
     }
 }
 
@@ -144,7 +165,11 @@ impl Iterator for FilePipeline {
         if self.stopped.load(Ordering::Relaxed) {
             return None;
         }
-        self.file_iter.next().map(Ok)
+        self.file_iter
+            .as_mut()
+            .unwrap_or_else(|| unreachable!("Option is always `Some`"))
+            .next()
+            .map(Ok)
     }
 }
 
@@ -166,7 +191,7 @@ mod tests {
     async fn file_pipeline_is_ok() {
         let file_size = 1024;
         let dir = tempfile::tempdir().unwrap();
-        let mut pipeline = FilePipeline::new(dir.as_ref().into(), file_size).unwrap();
+        let mut pipeline = FilePipeline::new(dir.as_ref().into(), file_size);
 
         let check_size = |mut file: LockedFile| {
             let file = file.into_std();