Preparatory pageserver async conversions (neondatabase#4773)

In neondatabase#4743, we'd like to convert the read path to use `async` rust. In
preparation of that, this PR switches some functions that are calling
lower level functions like `BlockReader::read_blk`,
`BlockCursor::read_blob`, etc into `async`. The PR does not switch all
functions however, and only focuses on the ones which are easy to
switch.

This leaves around some async functions that are (currently)
unnecessarily `async`, but on the other hand it makes future changes
smaller in diff.

Part of neondatabase#4743 (but does not completely address it).

pageserver/ctl/Cargo.toml

@@ -13,6 +13,7 @@ clap = { workspace = true, features = ["string"] }
 git-version.workspace = true
 pageserver = { path = ".." }
 postgres_ffi.workspace = true
+tokio.workspace = true
 utils.workspace = true
 svg_fmt.workspace = true
 workspace_hack.workspace = true

pageserver/ctl/src/layer_map_analyzer.rs

@@ -95,7 +95,7 @@ pub(crate) fn parse_filename(name: &str) -> Option<LayerFile> {
 }
 
 // Finds the max_holes largest holes, ignoring any that are smaller than MIN_HOLE_LENGTH"
-fn get_holes(path: &Path, max_holes: usize) -> Result<Vec<Hole>> {
+async fn get_holes(path: &Path, max_holes: usize) -> Result<Vec<Hole>> {
     let file = FileBlockReader::new(VirtualFile::open(path)?);
     let summary_blk = file.read_blk(0)?;
     let actual_summary = Summary::des_prefix(summary_blk.as_ref())?;
@@ -129,7 +129,7 @@ fn get_holes(path: &Path, max_holes: usize) -> Result<Vec<Hole>> {
     Ok(holes)
 }
 
-pub(crate) fn main(cmd: &AnalyzeLayerMapCmd) -> Result<()> {
+pub(crate) async fn main(cmd: &AnalyzeLayerMapCmd) -> Result<()> {
     let storage_path = &cmd.path;
     let max_holes = cmd.max_holes.unwrap_or(DEFAULT_MAX_HOLES);
 
@@ -160,7 +160,7 @@ pub(crate) fn main(cmd: &AnalyzeLayerMapCmd) -> Result<()> {
                     parse_filename(&layer.file_name().into_string().unwrap())
                 {
                     if layer_file.is_delta {
-                        layer_file.holes = get_holes(&layer.path(), max_holes)?;
+                        layer_file.holes = get_holes(&layer.path(), max_holes).await?;
                         n_deltas += 1;
                     }
                     layers.push(layer_file);

pageserver/ctl/src/layers.rs

@@ -43,8 +43,7 @@ pub(crate) enum LayerCmd {
     },
 }
 
-fn read_delta_file(path: impl AsRef<Path>) -> Result<()> {
-    use pageserver::tenant::blob_io::BlobCursor;
+async fn read_delta_file(path: impl AsRef<Path>) -> Result<()> {
     use pageserver::tenant::block_io::BlockReader;
 
     let path = path.as_ref();
@@ -78,7 +77,7 @@ fn read_delta_file(path: impl AsRef<Path>) -> Result<()> {
     Ok(())
 }
 
-pub(crate) fn main(cmd: &LayerCmd) -> Result<()> {
+pub(crate) async fn main(cmd: &LayerCmd) -> Result<()> {
     match cmd {
         LayerCmd::List { path } => {
             for tenant in fs::read_dir(path.join("tenants"))? {
@@ -153,7 +152,7 @@ pub(crate) fn main(cmd: &LayerCmd) -> Result<()> {
                         );
 
                         if layer_file.is_delta {
-                            read_delta_file(layer.path())?;
+                            read_delta_file(layer.path()).await?;
                         } else {
                             anyhow::bail!("not supported yet :(");
                         }

pageserver/ctl/src/main.rs

@@ -72,12 +72,13 @@ struct AnalyzeLayerMapCmd {
     max_holes: Option<usize>,
 }
 
-fn main() -> anyhow::Result<()> {
+#[tokio::main]
+async fn main() -> anyhow::Result<()> {
     let cli = CliOpts::parse();
 
     match cli.command {
         Commands::Layer(cmd) => {
-            layers::main(&cmd)?;
+            layers::main(&cmd).await?;
         }
         Commands::Metadata(cmd) => {
             handle_metadata(&cmd)?;
@@ -86,15 +87,15 @@ fn main() -> anyhow::Result<()> {
             draw_timeline_dir::main()?;
         }
         Commands::AnalyzeLayerMap(cmd) => {
-            layer_map_analyzer::main(&cmd)?;
+            layer_map_analyzer::main(&cmd).await?;
         }
         Commands::PrintLayerFile(cmd) => {
             if let Err(e) = read_pg_control_file(&cmd.path) {
                 println!(
                     "Failed to read input file as a pg control one: {e:#}\n\
                     Attempting to read it as layer file"
                 );
-                print_layerfile(&cmd.path)?;
+                print_layerfile(&cmd.path).await?;
             }
         }
     };
@@ -113,12 +114,12 @@ fn read_pg_control_file(control_file_path: &Path) -> anyhow::Result<()> {
     Ok(())
 }
 
-fn print_layerfile(path: &Path) -> anyhow::Result<()> {
+async fn print_layerfile(path: &Path) -> anyhow::Result<()> {
     // Basic initialization of things that don't change after startup
     virtual_file::init(10);
     page_cache::init(100);
     let ctx = RequestContext::new(TaskKind::DebugTool, DownloadBehavior::Error);
-    dump_layerfile_from_path(path, true, &ctx)
+    dump_layerfile_from_path(path, true, &ctx).await
 }
 
 fn handle_metadata(

pageserver/src/tenant.rs

@@ -3210,7 +3210,7 @@ impl Drop for Tenant {
     }
 }
 /// Dump contents of a layer file to stdout.
-pub fn dump_layerfile_from_path(
+pub async fn dump_layerfile_from_path(
     path: &Path,
     verbose: bool,
     ctx: &RequestContext,
@@ -3224,8 +3224,16 @@ pub fn dump_layerfile_from_path(
     file.read_exact_at(&mut header_buf, 0)?;
 
     match u16::from_be_bytes(header_buf) {
-        crate::IMAGE_FILE_MAGIC => ImageLayer::new_for_path(path, file)?.dump(verbose, ctx)?,
-        crate::DELTA_FILE_MAGIC => DeltaLayer::new_for_path(path, file)?.dump(verbose, ctx)?,
+        crate::IMAGE_FILE_MAGIC => {
+            ImageLayer::new_for_path(path, file)?
+                .dump(verbose, ctx)
+                .await?
+        }
+        crate::DELTA_FILE_MAGIC => {
+            DeltaLayer::new_for_path(path, file)?
+                .dump(verbose, ctx)
+                .await?
+        }
         magic => bail!("unrecognized magic identifier: {:?}", magic),
     }
 

pageserver/src/tenant/blob_io.rs

@@ -16,29 +16,19 @@ use crate::tenant::block_io::{BlockCursor, BlockReader};
 use std::cmp::min;
 use std::io::{Error, ErrorKind};
 
-/// For reading
-pub trait BlobCursor {
+impl<R> BlockCursor<R>
+where
+    R: BlockReader,
+{
     /// Read a blob into a new buffer.
-    fn read_blob(&mut self, offset: u64) -> Result<Vec<u8>, std::io::Error> {
+    pub fn read_blob(&mut self, offset: u64) -> Result<Vec<u8>, std::io::Error> {
         let mut buf = Vec::new();
         self.read_blob_into_buf(offset, &mut buf)?;
         Ok(buf)
     }
-
     /// Read blob into the given buffer. Any previous contents in the buffer
     /// are overwritten.
-    fn read_blob_into_buf(
-        &mut self,
-        offset: u64,
-        dstbuf: &mut Vec<u8>,
-    ) -> Result<(), std::io::Error>;
-}
-
-impl<R> BlobCursor for BlockCursor<R>
-where
-    R: BlockReader,
-{
-    fn read_blob_into_buf(
+    pub fn read_blob_into_buf(
         &mut self,
         offset: u64,
         dstbuf: &mut Vec<u8>,

pageserver/src/tenant/ephemeral_file.rs

@@ -328,7 +328,7 @@ fn to_io_error(e: anyhow::Error, context: &str) -> io::Error {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::tenant::blob_io::{BlobCursor, BlobWriter};
+    use crate::tenant::blob_io::BlobWriter;
     use crate::tenant::block_io::BlockCursor;
     use rand::{seq::SliceRandom, thread_rng, RngCore};
     use std::fs;

pageserver/src/tenant/layer_map.rs

@@ -626,17 +626,17 @@ impl LayerMap {
 
     /// debugging function to print out the contents of the layer map
     #[allow(unused)]
-    pub fn dump(&self, verbose: bool, ctx: &RequestContext) -> Result<()> {
+    pub async fn dump(&self, verbose: bool, ctx: &RequestContext) -> Result<()> {
         println!("Begin dump LayerMap");
 
         println!("open_layer:");
         if let Some(open_layer) = &self.open_layer {
-            open_layer.dump(verbose, ctx)?;
+            open_layer.dump(verbose, ctx).await?;
         }
 
         println!("frozen_layers:");
         for frozen_layer in self.frozen_layers.iter() {
-            frozen_layer.dump(verbose, ctx)?;
+            frozen_layer.dump(verbose, ctx).await?;
         }
 
         println!("historic_layers:");

pageserver/src/tenant/storage_layer.rs

@@ -338,7 +338,8 @@ impl LayerAccessStats {
 /// All layers should implement a minimal `std::fmt::Debug` without tenant or
 /// timeline names, because those are known in the context of which the layers
 /// are used in (timeline).
-pub trait Layer: std::fmt::Debug + std::fmt::Display + Send + Sync {
+#[async_trait::async_trait]
+pub trait Layer: std::fmt::Debug + std::fmt::Display + Send + Sync + 'static {
     /// Range of keys that this layer covers
     fn get_key_range(&self) -> Range<Key>;
 
@@ -368,7 +369,7 @@ pub trait Layer: std::fmt::Debug + std::fmt::Display + Send + Sync {
     /// is available. If this returns ValueReconstructResult::Continue, look up
     /// the predecessor layer and call again with the same 'reconstruct_data' to
     /// collect more data.
-    fn get_value_reconstruct_data(
+    async fn get_value_reconstruct_data(
         &self,
         key: Key,
         lsn_range: Range<Lsn>,
@@ -377,7 +378,7 @@ pub trait Layer: std::fmt::Debug + std::fmt::Display + Send + Sync {
     ) -> Result<ValueReconstructResult>;
 
     /// Dump summary of the contents of the layer to stdout
-    fn dump(&self, verbose: bool, ctx: &RequestContext) -> Result<()>;
+    async fn dump(&self, verbose: bool, ctx: &RequestContext) -> Result<()>;
 }
 
 /// Returned by [`PersistentLayer::iter`]

pageserver/src/tenant/storage_layer/delta_layer.rs

@@ -31,7 +31,7 @@ use crate::config::PageServerConf;
 use crate::context::RequestContext;
 use crate::page_cache::{PageReadGuard, PAGE_SZ};
 use crate::repository::{Key, Value, KEY_SIZE};
-use crate::tenant::blob_io::{BlobCursor, BlobWriter, WriteBlobWriter};
+use crate::tenant::blob_io::{BlobWriter, WriteBlobWriter};
 use crate::tenant::block_io::{BlockBuf, BlockCursor, BlockReader, FileBlockReader};
 use crate::tenant::disk_btree::{DiskBtreeBuilder, DiskBtreeReader, VisitDirection};
 use crate::tenant::storage_layer::{
@@ -223,9 +223,10 @@ impl std::fmt::Debug for DeltaLayerInner {
     }
 }
 
+#[async_trait::async_trait]
 impl Layer for DeltaLayer {
     /// debugging function to print out the contents of the layer
-    fn dump(&self, verbose: bool, ctx: &RequestContext) -> Result<()> {
+    async fn dump(&self, verbose: bool, ctx: &RequestContext) -> Result<()> {
         println!(
             "----- delta layer for ten {} tli {} keys {}-{} lsn {}-{} size {} ----",
             self.desc.tenant_id,
@@ -300,7 +301,7 @@ impl Layer for DeltaLayer {
         Ok(())
     }
 
-    fn get_value_reconstruct_data(
+    async fn get_value_reconstruct_data(
         &self,
         key: Key,
         lsn_range: Range<Lsn>,

pageserver/src/tenant/storage_layer/image_layer.rs

@@ -27,7 +27,7 @@ use crate::config::PageServerConf;
 use crate::context::RequestContext;
 use crate::page_cache::PAGE_SZ;
 use crate::repository::{Key, KEY_SIZE};
-use crate::tenant::blob_io::{BlobCursor, BlobWriter, WriteBlobWriter};
+use crate::tenant::blob_io::{BlobWriter, WriteBlobWriter};
 use crate::tenant::block_io::{BlockBuf, BlockReader, FileBlockReader};
 use crate::tenant::disk_btree::{DiskBtreeBuilder, DiskBtreeReader, VisitDirection};
 use crate::tenant::storage_layer::{
@@ -155,9 +155,10 @@ impl std::fmt::Debug for ImageLayerInner {
     }
 }
 
+#[async_trait::async_trait]
 impl Layer for ImageLayer {
     /// debugging function to print out the contents of the layer
-    fn dump(&self, verbose: bool, ctx: &RequestContext) -> Result<()> {
+    async fn dump(&self, verbose: bool, ctx: &RequestContext) -> Result<()> {
         println!(
             "----- image layer for ten {} tli {} key {}-{} at {} is_incremental {} size {} ----",
             self.desc.tenant_id,
@@ -189,7 +190,7 @@ impl Layer for ImageLayer {
     }
 
     /// Look up given page in the file
-    fn get_value_reconstruct_data(
+    async fn get_value_reconstruct_data(
         &self,
         key: Key,
         lsn_range: Range<Lsn>,

pageserver/src/tenant/storage_layer/inmemory_layer.rs

@@ -7,7 +7,7 @@
 use crate::config::PageServerConf;
 use crate::context::RequestContext;
 use crate::repository::{Key, Value};
-use crate::tenant::blob_io::{BlobCursor, BlobWriter};
+use crate::tenant::blob_io::BlobWriter;
 use crate::tenant::block_io::BlockReader;
 use crate::tenant::ephemeral_file::EphemeralFile;
 use crate::tenant::storage_layer::{ValueReconstructResult, ValueReconstructState};
@@ -110,6 +110,7 @@ impl InMemoryLayer {
     }
 }
 
+#[async_trait::async_trait]
 impl Layer for InMemoryLayer {
     fn get_key_range(&self) -> Range<Key> {
         Key::MIN..Key::MAX
@@ -132,7 +133,7 @@ impl Layer for InMemoryLayer {
     }
 
     /// debugging function to print out the contents of the layer
-    fn dump(&self, verbose: bool, _ctx: &RequestContext) -> Result<()> {
+    async fn dump(&self, verbose: bool, _ctx: &RequestContext) -> Result<()> {
         let inner = self.inner.read().unwrap();
 
         let end_str = inner
@@ -183,7 +184,7 @@ impl Layer for InMemoryLayer {
     }
 
     /// Look up given value in the layer.
-    fn get_value_reconstruct_data(
+    async fn get_value_reconstruct_data(
         &self,
         key: Key,
         lsn_range: Range<Lsn>,

pageserver/src/tenant/storage_layer/remote_layer.rs

@@ -65,8 +65,9 @@ impl std::fmt::Debug for RemoteLayer {
     }
 }
 
+#[async_trait::async_trait]
 impl Layer for RemoteLayer {
-    fn get_value_reconstruct_data(
+    async fn get_value_reconstruct_data(
         &self,
         _key: Key,
         _lsn_range: Range<Lsn>,
@@ -77,7 +78,7 @@ impl Layer for RemoteLayer {
     }
 
     /// debugging function to print out the contents of the layer
-    fn dump(&self, _verbose: bool, _ctx: &RequestContext) -> Result<()> {
+    async fn dump(&self, _verbose: bool, _ctx: &RequestContext) -> Result<()> {
         println!(
             "----- remote layer for ten {} tli {} keys {}-{} lsn {}-{} is_delta {} is_incremental {} size {} ----",
             self.desc.tenant_id,