refactor(tvix/store): Asyncify PathInfoService and DirectoryService r/6623

We've decided to asyncify all of the services to reduce some of the
pains going back and for between sync<->async. The end goal will be for
all the tvix-store internals to be async and then expose a sync
interface for things like tvix eval io.

Change-Id: I97c71f8db1d05a38bd8f625df5087d565705d52d
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9369
Autosubmit: Connor Brewster <cbrewster@hey.com>
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>

1 files changed, 15 insertions, 4 deletions

diff --git a/tvix/store/src/pathinfoservice/mod.rs b/tvix/store/src/pathinfoservice/mod.rs
index 51d3e51115eb..a460c35a0289 100644
--- a/tvix/store/src/pathinfoservice/mod.rs
+++ b/tvix/store/src/pathinfoservice/mod.rs
@@ -3,8 +3,12 @@ mod grpc;
 mod memory;
 mod sled;
 
+use std::pin::Pin;
 use std::sync::Arc;
 
+use futures::Stream;
+use tonic::async_trait;
+
 use crate::blobservice::BlobService;
 use crate::directoryservice::DirectoryService;
 use crate::{proto, Error};
@@ -16,10 +20,12 @@ pub use self::sled::SledPathInfoService;
 
 /// The base trait all PathInfo services need to implement.
 /// This is a simple get and put of [proto::Directory], returning their digest.
+#[async_trait]
 pub trait PathInfoService: Send + Sync {
     /// Create a new instance by passing in a connection URL, as well
     /// as instances of a [PathInfoService] and [DirectoryService] (as the
     /// [PathInfoService] needs to talk to them).
+    /// TODO: check if we want to make this async, instead of lazily connecting
     fn from_url(
         url: &url::Url,
         blob_service: Arc<dyn BlobService>,
@@ -29,18 +35,23 @@ pub trait PathInfoService: Send + Sync {
         Self: Sized;
 
     /// Retrieve a PathInfo message by the output digest.
-    fn get(&self, digest: [u8; 20]) -> Result<Option<proto::PathInfo>, Error>;
+    async fn get(&self, digest: [u8; 20]) -> Result<Option<proto::PathInfo>, Error>;
 
     /// Store a PathInfo message. Implementations MUST call validate and reject
     /// invalid messages.
-    fn put(&self, path_info: proto::PathInfo) -> Result<proto::PathInfo, Error>;
+    async fn put(&self, path_info: proto::PathInfo) -> Result<proto::PathInfo, Error>;
 
     /// Return the nar size and nar sha256 digest for a given root node.
     /// This can be used to calculate NAR-based output paths,
     /// and implementations are encouraged to cache it.
-    fn calculate_nar(&self, root_node: &proto::node::Node) -> Result<(u64, [u8; 32]), Error>;
+    async fn calculate_nar(&self, root_node: &proto::node::Node) -> Result<(u64, [u8; 32]), Error>;
 
     /// Iterate over all PathInfo objects in the store.
     /// Implementations can decide to disallow listing.
-    fn list(&self) -> Box<dyn Iterator<Item = Result<proto::PathInfo, Error>> + Send + '_>;
+    ///
+    /// This returns a pinned, boxed stream. The pinning allows for it to be polled easily,
+    /// and the box allows different underlying stream implementations to be returned since
+    /// Rust doesn't support this as a generic in traits yet. This is the same thing that
+    /// [async_trait] generates, but for streams instead of futures.
+    fn list(&self) -> Pin<Box<dyn Stream<Item = Result<proto::PathInfo, Error>> + Send>>;
 }