Compaction: unify key and value reference vecs

pageserver/src/tenant/storage_layer/delta_layer.rs

@@ -549,25 +549,10 @@ impl DeltaLayer {
             &self.layer_name(),
         )
     }
-
-    /// Obtains all keys and value references stored in the layer
+    /// Loads all keys stored in the layer. Returns key, lsn, value size and value reference.
     ///
     /// The value can be obtained via the [`ValueRef::load`] function.
-    pub async fn load_val_refs(
-        &self,
-        ctx: &RequestContext,
-    ) -> Result<Vec<(Key, Lsn, ValueRef<Arc<DeltaLayerInner>>)>> {
-        let inner = self
-            .load(LayerAccessKind::Iter, ctx)
-            .await
-            .context("load delta layer")?;
-        DeltaLayerInner::load_val_refs(inner)
-            .await
-            .context("Layer index is corrupted")
-    }
-
-    /// Loads all keys stored in the layer. Returns key, lsn and value size.
-    pub async fn load_keys(&self, ctx: &RequestContext) -> Result<Vec<(Key, Lsn, u64)>> {
+    pub async fn load_keys(&self, ctx: &RequestContext) -> Result<Vec<DeltaEntry>> {
         let inner = self
             .load(LayerAccessKind::KeyIter, ctx)
             .await
@@ -711,6 +696,17 @@ impl DeltaLayerWriterInner {
             .metadata()
             .context("get file metadata to determine size")?;
 
+        // 5GB limit for objects without multipart upload (which we don't want to use)
+        // Make it a little bit below to account for differing GB units
+        // https://docs.aws.amazon.com/AmazonS3/latest/userguide/upload-objects.html
+        const S3_UPLOAD_LIMIT: u64 = 4_500_000_000;
+        ensure!(
+            metadata.len() <= S3_UPLOAD_LIMIT,
+            "Created delta layer file at {} of size {} above limit {S3_UPLOAD_LIMIT}!",
+            file.path.display(),
+            metadata.len()
+        );
+
         // Note: Because we opened the file in write-only mode, we cannot
         // reuse the same VirtualFile for reading later. That's why we don't
         // set inner.file here. The first read will have to re-open it.
@@ -955,15 +951,17 @@ impl DeltaLayerInner {
         }
     }
 
-    pub(super) async fn load_val_refs<T: AsRef<DeltaLayerInner> + Clone>(
+    pub(super) async fn load_keys<T: AsRef<DeltaLayerInner> + Clone>(
         this: &T,
-    ) -> Result<Vec<(Key, Lsn, ValueRef<T>)>> {
+    ) -> Result<Vec<DeltaEntry>> {
         let dl = this.as_ref();
         let file = &dl.file;
+
         let tree_reader =
             DiskBtreeReader::<_, DELTA_KEY_SIZE>::new(dl.index_start_blk, dl.index_root_blk, file);
 
-        let mut all_offsets = Vec::<(Key, Lsn, ValueRef<T>)>::new();
+        let mut all_keys: Vec<DeltaEntry> = Vec::new();
+
         tree_reader
             .visit(
                 &[0u8; DELTA_KEY_SIZE],
@@ -972,56 +970,45 @@ impl DeltaLayerInner {
                     let delta_key = DeltaKey::from_slice(key);
                     let val_ref = ValueRef {
                         blob_ref: BlobRef(value),
-                        reader: BlockCursor::new(Adapter(this.clone())),
+                        reader: BlockCursor::new(Adapter(dl)),
                     };
-                    all_offsets.push((delta_key.key(), delta_key.lsn(), val_ref));
-                    true
-                },
-            )
-            .await?;
-
-        Ok(all_offsets)
-    }
-
-    pub(super) async fn load_keys(&self) -> Result<Vec<(Key, Lsn, u64)>> {
-        let file = &self.file;
-        let tree_reader = DiskBtreeReader::<_, DELTA_KEY_SIZE>::new(
-            self.index_start_blk,
-            self.index_root_blk,
-            file,
-        );
-
-        let mut all_keys: Vec<(Key, Lsn, u64)> = Vec::new();
-        tree_reader
-            .visit(
-                &[0u8; DELTA_KEY_SIZE],
-                VisitDirection::Forwards,
-                |key, value| {
-                    let delta_key = DeltaKey::from_slice(key);
                     let pos = BlobRef(value).pos();
                     if let Some(last) = all_keys.last_mut() {
-                        if last.0 == delta_key.key() {
-                            return true;
-                        } else {
-                            // subtract offset of new key BLOB and first blob of this key
-                            // to get total size if values associated with this key
-                            let first_pos = last.2;
-                            last.2 = pos - first_pos;
-                        }
+                        // subtract offset of the current and last entries to get the size
+                        // of the value associated with this (key, lsn) tuple
+                        let first_pos = last.size;
+                        last.size = pos - first_pos;
                     }
-                    all_keys.push((delta_key.key(), delta_key.lsn(), pos));
+                    let entry = DeltaEntry {
+                        key: delta_key.key(),
+                        lsn: delta_key.lsn(),
+                        size: pos,
+                        val: val_ref,
+                    };
+                    all_keys.push(entry);
                     true
                 },
             )
             .await?;
         if let Some(last) = all_keys.last_mut() {
-            // Last key occupies all space till end of layer
-            last.2 = std::fs::metadata(&file.file.path)?.len() - last.2;
+            // Last key occupies all space till end of value storage,
+            // which corresponds to beginning of the index
+            last.size = dl.index_start_blk as u64 * PAGE_SZ as u64 - last.size;
         }
         Ok(all_keys)
     }
 }
 
+/// A set of data associated with a delta layer key and its value
+pub struct DeltaEntry<'a> {
+    pub key: Key,
+    pub lsn: Lsn,
+    /// Size of the stored value
+    pub size: u64,
+    /// Reference to the on-disk value
+    pub val: ValueRef<&'a DeltaLayerInner>,
+}
+
 /// Reference to an on-disk value
 pub struct ValueRef<T: AsRef<DeltaLayerInner>> {
     blob_ref: BlobRef,

pageserver/src/tenant/timeline.rs

@@ -39,6 +39,7 @@ use crate::context::{
     AccessStatsBehavior, DownloadBehavior, RequestContext, RequestContextBuilder,
 };
 use crate::tenant::remote_timeline_client::{self, index::LayerFileMetadata};
+use crate::tenant::storage_layer::delta_layer::DeltaEntry;
 use crate::tenant::storage_layer::{
     DeltaFileName, DeltaLayerWriter, ImageFileName, ImageLayerWriter, InMemoryLayer,
     LayerAccessStats, LayerFileName, RemoteLayer,
@@ -3312,10 +3313,10 @@ struct CompactLevel0Phase1StatsBuilder {
     timeline_id: Option<TimelineId>,
     read_lock_acquisition_micros: DurationRecorder,
     read_lock_held_spawn_blocking_startup_micros: DurationRecorder,
+    read_lock_held_key_sort_micros: DurationRecorder,
     read_lock_held_prerequisites_micros: DurationRecorder,
     read_lock_held_compute_holes_micros: DurationRecorder,
     read_lock_drop_micros: DurationRecorder,
-    prepare_iterators_micros: DurationRecorder,
     write_layer_files_micros: DurationRecorder,
     level0_deltas_count: Option<usize>,
     new_deltas_count: Option<usize>,
@@ -3332,10 +3333,10 @@ struct CompactLevel0Phase1Stats {
     timeline_id: TimelineId,
     read_lock_acquisition_micros: RecordedDuration,
     read_lock_held_spawn_blocking_startup_micros: RecordedDuration,
+    read_lock_held_key_sort_micros: RecordedDuration,
     read_lock_held_prerequisites_micros: RecordedDuration,
     read_lock_held_compute_holes_micros: RecordedDuration,
     read_lock_drop_micros: RecordedDuration,
-    prepare_iterators_micros: RecordedDuration,
     write_layer_files_micros: RecordedDuration,
     level0_deltas_count: usize,
     new_deltas_count: usize,
@@ -3362,6 +3363,10 @@ impl TryFrom<CompactLevel0Phase1StatsBuilder> for CompactLevel0Phase1Stats {
                 .read_lock_held_spawn_blocking_startup_micros
                 .into_recorded()
                 .ok_or_else(|| anyhow!("read_lock_held_spawn_blocking_startup_micros not set"))?,
+            read_lock_held_key_sort_micros: value
+                .read_lock_held_key_sort_micros
+                .into_recorded()
+                .ok_or_else(|| anyhow!("read_lock_held_key_sort_micros not set"))?,
             read_lock_held_prerequisites_micros: value
                 .read_lock_held_prerequisites_micros
                 .into_recorded()
@@ -3374,10 +3379,6 @@ impl TryFrom<CompactLevel0Phase1StatsBuilder> for CompactLevel0Phase1Stats {
                 .read_lock_drop_micros
                 .into_recorded()
                 .ok_or_else(|| anyhow!("read_lock_drop_micros not set"))?,
-            prepare_iterators_micros: value
-                .prepare_iterators_micros
-                .into_recorded()
-                .ok_or_else(|| anyhow!("prepare_iterators_micros not set"))?,
             write_layer_files_micros: value
                 .write_layer_files_micros
                 .into_recorded()
@@ -3547,28 +3548,24 @@ impl Timeline {
         let mut heap: BinaryHeap<Hole> = BinaryHeap::with_capacity(max_holes + 1);
         let mut prev: Option<Key> = None;
 
-        let mut all_value_refs = Vec::new();
         let mut all_keys = Vec::new();
 
-        for l in deltas_to_compact.iter() {
+        let downcast_deltas: Vec<_> = deltas_to_compact
+            .iter()
+            .map(|l| l.clone().downcast_delta_layer().expect("delta layer"))
+            .collect();
+        for dl in downcast_deltas.iter() {
             // TODO: replace this with an await once we fully go async
-            let delta = l.clone().downcast_delta_layer().expect("delta layer");
-            Handle::current().block_on(async {
-                all_value_refs.extend(delta.load_val_refs(ctx).await?);
-                all_keys.extend(delta.load_keys(ctx).await?);
-                anyhow::Ok(())
-            })?;
+            all_keys.extend(Handle::current().block_on(DeltaLayer::load_keys(dl, ctx))?);
         }
 
         // The current stdlib sorting implementation is designed in a way where it is
         // particularly fast where the slice is made up of sorted sub-ranges.
-        all_value_refs.sort_by_key(|(key, lsn, _value_ref)| (*key, *lsn));
+        all_keys.sort_by_key(|DeltaEntry { key, lsn, .. }| (*key, *lsn));
 
-        // The current stdlib sorting implementation is designed in a way where it is
-        // particularly fast where the slice is made up of sorted sub-ranges.
-        all_keys.sort_by_key(|(key, lsn, _size)| (*key, *lsn));
+        stats.read_lock_held_key_sort_micros = stats.read_lock_held_prerequisites_micros.till_now();
 
-        for (next_key, _next_lsn, _size) in all_keys.iter() {
+        for DeltaEntry { key: next_key, .. } in all_keys.iter() {
             let next_key = *next_key;
             if let Some(prev_key) = prev {
                 // just first fast filter
@@ -3592,8 +3589,7 @@ impl Timeline {
             }
             prev = Some(next_key.next());
         }
-        stats.read_lock_held_compute_holes_micros =
-            stats.read_lock_held_prerequisites_micros.till_now();
+        stats.read_lock_held_compute_holes_micros = stats.read_lock_held_key_sort_micros.till_now();
         drop_rlock(guard);
         stats.read_lock_drop_micros = stats.read_lock_held_compute_holes_micros.till_now();
         let mut holes = heap.into_vec();
@@ -3602,12 +3598,26 @@ impl Timeline {
 
         // This iterator walks through all key-value pairs from all the layers
         // we're compacting, in key, LSN order.
-        let all_values_iter = all_value_refs.into_iter();
+        let all_values_iter = all_keys.iter();
 
         // This iterator walks through all keys and is needed to calculate size used by each key
-        let mut all_keys_iter = all_keys.into_iter();
-
-        stats.prepare_iterators_micros = stats.read_lock_drop_micros.till_now();
+        let mut all_keys_iter = all_keys
+            .iter()
+            .map(|DeltaEntry { key, lsn, size, .. }| (*key, *lsn, *size))
+            .coalesce(|mut prev, cur| {
+                // Coalesce keys that belong to the same key pair.
+                // This ensures that compaction doesn't put them
+                // into different layer files.
+                // Still limit this by the target file size,
+                // so that we keep the size of the files in
+                // check.
+                if prev.0 == cur.0 && prev.2 < target_file_size {
+                    prev.2 += cur.2;
+                    Ok(prev)
+                } else {
+                    Err((prev, cur))
+                }
+            });
 
         // Merge the contents of all the input delta layers into a new set
         // of delta layers, based on the current partitioning.
@@ -3662,8 +3672,11 @@ impl Timeline {
 
         // TODO remove this block_on wrapper once we fully go async
         Handle::current().block_on(async {
-            for (key, lsn, value_ref) in all_values_iter {
-                let value = value_ref.load().await?;
+            for &DeltaEntry {
+                key, lsn, ref val, ..
+            } in all_values_iter
+            {
+                let value = val.load().await?;
                 let same_key = prev_key.map_or(false, |prev_key| prev_key == key);
                 // We need to check key boundaries once we reach next key or end of layer with the same key
                 if !same_key || lsn == dup_end_lsn {
@@ -3764,6 +3777,16 @@ impl Timeline {
 
         // Sync layers
         if !new_layers.is_empty() {
+            // Print a warning if the created layer is larger than double the target size
+            let warn_limit = target_file_size * 2;
+            for layer in new_layers.iter() {
+                if layer.desc.file_size > warn_limit {
+                    warn!(
+                        %layer,
+                        "created delta file of size {} larger than double of target of {target_file_size}", layer.desc.file_size
+                    );
+                }
+            }
             let mut layer_paths: Vec<PathBuf> = new_layers.iter().map(|l| l.path()).collect();
 
             // Fsync all the layer files and directory using multiple threads to
@@ -3776,12 +3799,10 @@ impl Timeline {
             layer_paths.pop().unwrap();
         }
 
-        stats.write_layer_files_micros = stats.prepare_iterators_micros.till_now();
+        stats.write_layer_files_micros = stats.read_lock_drop_micros.till_now();
         stats.new_deltas_count = Some(new_layers.len());
         stats.new_deltas_size = Some(new_layers.iter().map(|l| l.desc.file_size).sum());
 
-        drop(all_keys_iter); // So that deltas_to_compact is no longer borrowed
-
         match TryInto::<CompactLevel0Phase1Stats>::try_into(stats)
             .and_then(|stats| serde_json::to_string(&stats).context("serde_json::to_string"))
         {