refactor(tvix/store/blobsvc): make BlobStore async r/6606

We previously kept the trait of a BlobService sync.

This however had some annoying consequences:

 - It became more and more complicated to track when we're in a context
   with an async runtime in the context or not, producing bugs like
   https://b.tvl.fyi/issues/304
 - The sync trait shielded away async clients from async worloads,
   requiring manual block_on code inside the gRPC client code, and
   spawn_blocking calls in consumers of the trait, even if they were
   async (like the gRPC server)
 - We had to write our own custom glue code (SyncReadIntoAsyncRead)
   to convert a sync io::Read into a tokio::io::AsyncRead, which already
   existed in tokio internally, but upstream ia hesitant to expose.

This now makes the BlobService trait async (via the async_trait macro,
like we already do in various gRPC parts), and replaces the sync readers
and writers with their async counterparts.

Tests interacting with a BlobService now need to have an async runtime
available, the easiest way for this is to mark the test functions
with the tokio::test macro, allowing us to directly .await in the test
function.

In places where we don't have an async runtime available from context
(like tvix-cli), we can pass one down explicitly.

Now that we don't provide a sync interface anymore, the (sync) FUSE
library now holds a pointer to a tokio runtime handle, and needs to at
least have 2 threads available when talking to a blob service (which is
why some of the tests now use the multi_thread flavor).

The FUSE tests got a bit more verbose, as we couldn't use the
setup_and_mount function accepting a callback anymore. We can hopefully
move some of the test fixture setup to rstest in the future to make this
less repetitive.

Co-Authored-By: Connor Brewster <cbrewster@hey.com>
Change-Id: Ia0501b606e32c852d0108de9c9016b21c94a3c05
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9329
Reviewed-by: Connor Brewster <cbrewster@hey.com>
Tested-by: BuildkiteCI
Reviewed-by: raitobezarius <tvl@lahfa.xyz>

1 files changed, 21 insertions, 32 deletions

diff --git a/tvix/store/src/proto/grpc_blobservice_wrapper.rs b/tvix/store/src/proto/grpc_blobservice_wrapper.rs
index 2d8c396539d8..8bd3083c17ad 100644
--- a/tvix/store/src/proto/grpc_blobservice_wrapper.rs
+++ b/tvix/store/src/proto/grpc_blobservice_wrapper.rs
@@ -1,4 +1,6 @@
-use crate::{blobservice::BlobService, proto::sync_read_into_async_read::SyncReadIntoAsyncRead};
+use crate::blobservice::BlobService;
+use core::pin::pin;
+use futures::TryFutureExt;
 use std::{
     collections::VecDeque,
     io,
@@ -6,7 +8,6 @@ use std::{
     pin::Pin,
     sync::Arc,
 };
-use tokio::task;
 use tokio_stream::StreamExt;
 use tokio_util::io::ReaderStream;
 use tonic::{async_trait, Request, Response, Status, Streaming};
@@ -103,7 +104,7 @@ impl super::blob_service_server::BlobService for GRPCBlobServiceWrapper {
             return Err(Status::internal("not implemented"));
         }
 
-        match self.blob_service.has(&req_digest) {
+        match self.blob_service.has(&req_digest).await {
             Ok(true) => Ok(Response::new(super::BlobMeta::default())),
             Ok(false) => Err(Status::not_found(format!("blob {} not found", &req_digest))),
             Err(e) => Err(e.into()),
@@ -122,13 +123,8 @@ impl super::blob_service_server::BlobService for GRPCBlobServiceWrapper {
             .try_into()
             .map_err(|_e| Status::invalid_argument("invalid digest length"))?;
 
-        match self.blob_service.open_read(&req_digest) {
+        match self.blob_service.open_read(&req_digest).await {
             Ok(Some(reader)) => {
-                let async_reader: SyncReadIntoAsyncRead<
-                    _,
-                    BytesMutWithDefaultCapacity<{ 100 * 1024 }>,
-                > = reader.into();
-
                 fn stream_mapper(
                     x: Result<bytes::Bytes, io::Error>,
                 ) -> Result<super::BlobChunk, Status> {
@@ -138,7 +134,7 @@ impl super::blob_service_server::BlobService for GRPCBlobServiceWrapper {
                     }
                 }
 
-                let chunks_stream = ReaderStream::new(async_reader).map(stream_mapper);
+                let chunks_stream = ReaderStream::new(reader).map(stream_mapper);
                 Ok(Response::new(Box::pin(chunks_stream)))
             }
             Ok(None) => Err(Status::not_found(format!("blob {} not found", &req_digest))),
@@ -158,35 +154,28 @@ impl super::blob_service_server::BlobService for GRPCBlobServiceWrapper {
                 .map_err(|e| std::io::Error::new(std::io::ErrorKind::InvalidInput, e))
         });
 
-        let data_reader = tokio_util::io::StreamReader::new(data_stream);
-
-        // prepare a writer, which we'll use in the blocking task below.
-        let mut writer = self.blob_service.open_write();
+        let mut data_reader = tokio_util::io::StreamReader::new(data_stream);
 
-        let result = task::spawn_blocking(move || -> Result<super::PutBlobResponse, Status> {
-            // construct a sync reader to the data
-            let mut reader = tokio_util::io::SyncIoBridge::new(data_reader);
+        let mut blob_writer = pin!(self.blob_service.open_write().await);
 
-            io::copy(&mut reader, &mut writer).map_err(|e| {
+        tokio::io::copy(&mut data_reader, &mut blob_writer)
+            .await
+            .map_err(|e| {
                 warn!("error copying: {}", e);
                 Status::internal("error copying")
             })?;
 
-            let digest = writer
-                .close()
-                .map_err(|e| {
-                    warn!("error closing stream: {}", e);
-                    Status::internal("error closing stream")
-                })?
-                .to_vec();
-
-            Ok(super::PutBlobResponse {
-                digest: digest.into(),
+        let digest = blob_writer
+            .close()
+            .map_err(|e| {
+                warn!("error closing stream: {}", e);
+                Status::internal("error closing stream")
             })
-        })
-        .await
-        .map_err(|_| Status::internal("failed to wait for task"))??;
+            .await?
+            .to_vec();
 
-        Ok(Response::new(result))
+        Ok(Response::new(super::PutBlobResponse {
+            digest: digest.into(),
+        }))
     }
 }