The fix of #2650. (#2686)

* Wrappers and drop implementations for image and delta layer writers.
* Two regression tests for the image and delta layer files.

pageserver/src/tenant/delta_layer.rs

@@ -610,9 +610,9 @@ impl DeltaLayer {
 ///
 /// 3. Call `finish`.
 ///
-pub struct DeltaLayerWriter {
+struct DeltaLayerWriterInner {
     conf: &'static PageServerConf,
-    path: PathBuf,
+    pub path: PathBuf,
     timeline_id: TimelineId,
     tenant_id: TenantId,
 
@@ -624,17 +624,17 @@ pub struct DeltaLayerWriter {
     blob_writer: WriteBlobWriter<BufWriter<VirtualFile>>,
 }
 
-impl DeltaLayerWriter {
+impl DeltaLayerWriterInner {
     ///
     /// Start building a new delta layer.
     ///
-    pub fn new(
+    fn new(
         conf: &'static PageServerConf,
         timeline_id: TimelineId,
         tenant_id: TenantId,
         key_start: Key,
         lsn_range: Range<Lsn>,
-    ) -> Result<DeltaLayerWriter> {
+    ) -> anyhow::Result<Self> {
         // Create the file initially with a temporary filename. We don't know
         // the end key yet, so we cannot form the final filename yet. We will
         // rename it when we're done.
@@ -653,7 +653,7 @@ impl DeltaLayerWriter {
         let block_buf = BlockBuf::new();
         let tree_builder = DiskBtreeBuilder::new(block_buf);
 
-        Ok(DeltaLayerWriter {
+        Ok(Self {
             conf,
             path,
             timeline_id,
@@ -670,17 +670,17 @@ impl DeltaLayerWriter {
     ///
     /// The values must be appended in key, lsn order.
     ///
-    pub fn put_value(&mut self, key: Key, lsn: Lsn, val: Value) -> Result<()> {
+    fn put_value(&mut self, key: Key, lsn: Lsn, val: Value) -> anyhow::Result<()> {
         self.put_value_bytes(key, lsn, &Value::ser(&val)?, val.will_init())
     }
 
-    pub fn put_value_bytes(
+    fn put_value_bytes(
         &mut self,
         key: Key,
         lsn: Lsn,
         val: &[u8],
         will_init: bool,
-    ) -> Result<()> {
+    ) -> anyhow::Result<()> {
         assert!(self.lsn_range.start <= lsn);
 
         let off = self.blob_writer.write_blob(val)?;
@@ -693,14 +693,14 @@ impl DeltaLayerWriter {
         Ok(())
     }
 
-    pub fn size(&self) -> u64 {
+    fn size(&self) -> u64 {
         self.blob_writer.size() + self.tree.borrow_writer().size()
     }
 
     ///
     /// Finish writing the delta layer.
     ///
-    pub fn finish(self, key_end: Key) -> anyhow::Result<DeltaLayer> {
+    fn finish(self, key_end: Key) -> anyhow::Result<DeltaLayer> {
         let index_start_blk =
             ((self.blob_writer.size() + PAGE_SZ as u64 - 1) / PAGE_SZ as u64) as u32;
 
@@ -768,6 +768,102 @@ impl DeltaLayerWriter {
     }
 }
 
+/// A builder object for constructing a new delta layer.
+///
+/// Usage:
+///
+/// 1. Create the DeltaLayerWriter by calling DeltaLayerWriter::new(...)
+///
+/// 2. Write the contents by calling `put_value` for every page
+///    version to store in the layer.
+///
+/// 3. Call `finish`.
+///
+/// # Note
+///
+/// As described in https://github.com/neondatabase/neon/issues/2650, it's
+/// possible for the writer to drop before `finish` is actually called. So this
+/// could lead to odd temporary files in the directory, exhausting file system.
+/// This structure wraps `DeltaLayerWriterInner` and also contains `Drop`
+/// implementation that cleans up the temporary file in failure. It's not
+/// possible to do this directly in `DeltaLayerWriterInner` since `finish` moves
+/// out some fields, making it impossible to implement `Drop`.
+///
+#[must_use]
+pub struct DeltaLayerWriter {
+    inner: Option<DeltaLayerWriterInner>,
+}
+
+impl DeltaLayerWriter {
+    ///
+    /// Start building a new delta layer.
+    ///
+    pub fn new(
+        conf: &'static PageServerConf,
+        timeline_id: TimelineId,
+        tenant_id: TenantId,
+        key_start: Key,
+        lsn_range: Range<Lsn>,
+    ) -> anyhow::Result<Self> {
+        Ok(Self {
+            inner: Some(DeltaLayerWriterInner::new(
+                conf,
+                timeline_id,
+                tenant_id,
+                key_start,
+                lsn_range,
+            )?),
+        })
+    }
+
+    ///
+    /// Append a key-value pair to the file.
+    ///
+    /// The values must be appended in key, lsn order.
+    ///
+    pub fn put_value(&mut self, key: Key, lsn: Lsn, val: Value) -> anyhow::Result<()> {
+        self.inner.as_mut().unwrap().put_value(key, lsn, val)
+    }
+
+    pub fn put_value_bytes(
+        &mut self,
+        key: Key,
+        lsn: Lsn,
+        val: &[u8],
+        will_init: bool,
+    ) -> anyhow::Result<()> {
+        self.inner
+            .as_mut()
+            .unwrap()
+            .put_value_bytes(key, lsn, val, will_init)
+    }
+
+    pub fn size(&self) -> u64 {
+        self.inner.as_ref().unwrap().size()
+    }
+
+    ///
+    /// Finish writing the delta layer.
+    ///
+    pub fn finish(mut self, key_end: Key) -> anyhow::Result<DeltaLayer> {
+        self.inner.take().unwrap().finish(key_end)
+    }
+}
+
+impl Drop for DeltaLayerWriter {
+    fn drop(&mut self) {
+        if let Some(inner) = self.inner.take() {
+            match inner.blob_writer.into_inner().into_inner() {
+                Ok(vfile) => vfile.remove(),
+                Err(err) => warn!(
+                    "error while flushing buffer of image layer temporary file: {}",
+                    err
+                ),
+            }
+        }
+    }
+}
+
 ///
 /// Iterator over all key-value pairse stored in a delta layer
 ///

pageserver/src/tenant/image_layer.rs

@@ -411,7 +411,7 @@ impl ImageLayer {
 ///
 /// 3. Call `finish`.
 ///
-pub struct ImageLayerWriter {
+struct ImageLayerWriterInner {
     conf: &'static PageServerConf,
     path: PathBuf,
     timeline_id: TimelineId,
@@ -423,14 +423,17 @@ pub struct ImageLayerWriter {
     tree: DiskBtreeBuilder<BlockBuf, KEY_SIZE>,
 }
 
-impl ImageLayerWriter {
-    pub fn new(
+impl ImageLayerWriterInner {
+    ///
+    /// Start building a new image layer.
+    ///
+    fn new(
         conf: &'static PageServerConf,
         timeline_id: TimelineId,
         tenant_id: TenantId,
         key_range: &Range<Key>,
         lsn: Lsn,
-    ) -> anyhow::Result<ImageLayerWriter> {
+    ) -> anyhow::Result<Self> {
         // Create the file initially with a temporary filename.
         // We'll atomically rename it to the final name when we're done.
         let path = ImageLayer::temp_path_for(
@@ -455,7 +458,7 @@ impl ImageLayerWriter {
         let block_buf = BlockBuf::new();
         let tree_builder = DiskBtreeBuilder::new(block_buf);
 
-        let writer = ImageLayerWriter {
+        let writer = Self {
             conf,
             path,
             timeline_id,
@@ -474,7 +477,7 @@ impl ImageLayerWriter {
     ///
     /// The page versions must be appended in blknum order.
     ///
-    pub fn put_image(&mut self, key: Key, img: &[u8]) -> Result<()> {
+    fn put_image(&mut self, key: Key, img: &[u8]) -> anyhow::Result<()> {
         ensure!(self.key_range.contains(&key));
         let off = self.blob_writer.write_blob(img)?;
 
@@ -485,7 +488,10 @@ impl ImageLayerWriter {
         Ok(())
     }
 
-    pub fn finish(self) -> anyhow::Result<ImageLayer> {
+    ///
+    /// Finish writing the image layer.
+    ///
+    fn finish(self) -> anyhow::Result<ImageLayer> {
         let index_start_blk =
             ((self.blob_writer.size() + PAGE_SZ as u64 - 1) / PAGE_SZ as u64) as u32;
 
@@ -552,3 +558,76 @@ impl ImageLayerWriter {
         Ok(layer)
     }
 }
+
+/// A builder object for constructing a new image layer.
+///
+/// Usage:
+///
+/// 1. Create the ImageLayerWriter by calling ImageLayerWriter::new(...)
+///
+/// 2. Write the contents by calling `put_page_image` for every key-value
+///    pair in the key range.
+///
+/// 3. Call `finish`.
+///
+/// # Note
+///
+/// As described in https://github.com/neondatabase/neon/issues/2650, it's
+/// possible for the writer to drop before `finish` is actually called. So this
+/// could lead to odd temporary files in the directory, exhausting file system.
+/// This structure wraps `ImageLayerWriterInner` and also contains `Drop`
+/// implementation that cleans up the temporary file in failure. It's not
+/// possible to do this directly in `ImageLayerWriterInner` since `finish` moves
+/// out some fields, making it impossible to implement `Drop`.
+///
+#[must_use]
+pub struct ImageLayerWriter {
+    inner: Option<ImageLayerWriterInner>,
+}
+
+impl ImageLayerWriter {
+    ///
+    /// Start building a new image layer.
+    ///
+    pub fn new(
+        conf: &'static PageServerConf,
+        timeline_id: TimelineId,
+        tenant_id: TenantId,
+        key_range: &Range<Key>,
+        lsn: Lsn,
+    ) -> anyhow::Result<ImageLayerWriter> {
+        Ok(Self {
+            inner: Some(ImageLayerWriterInner::new(
+                conf,
+                timeline_id,
+                tenant_id,
+                key_range,
+                lsn,
+            )?),
+        })
+    }
+
+    ///
+    /// Write next value to the file.
+    ///
+    /// The page versions must be appended in blknum order.
+    ///
+    pub fn put_image(&mut self, key: Key, img: &[u8]) -> anyhow::Result<()> {
+        self.inner.as_mut().unwrap().put_image(key, img)
+    }
+
+    ///
+    /// Finish writing the image layer.
+    ///
+    pub fn finish(mut self) -> anyhow::Result<ImageLayer> {
+        self.inner.take().unwrap().finish()
+    }
+}
+
+impl Drop for ImageLayerWriter {
+    fn drop(&mut self) {
+        if let Some(inner) = self.inner.take() {
+            inner.blob_writer.into_inner().remove();
+        }
+    }
+}

pageserver/src/tenant/timeline.rs

@@ -1541,6 +1541,10 @@ impl Timeline {
                     lsn,
                 )?;
 
+                fail_point!("image-layer-writer-fail-before-finish", |_| {
+                    anyhow::bail!("failpoint image-layer-writer-fail-before-finish");
+                });
+
                 for range in &partition.ranges {
                     let mut key = range.start;
                     while key < range.end {
@@ -1835,6 +1839,11 @@ impl Timeline {
                     },
                 )?);
             }
+
+            fail_point!("delta-layer-writer-fail-before-finish", |_| {
+                anyhow::bail!("failpoint delta-layer-writer-fail-before-finish");
+            });
+
             writer.as_mut().unwrap().put_value(key, lsn, value)?;
             prev_key = Some(key);
         }

pageserver/src/virtual_file.rs

@@ -319,6 +319,12 @@ impl VirtualFile {
 
         Ok(result)
     }
+
+    pub fn remove(self) {
+        let path = self.path.clone();
+        drop(self);
+        std::fs::remove_file(path).expect("failed to remove the virtual file");
+    }
 }
 
 impl Drop for VirtualFile {