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, 2 insertions, 1 deletions

diff --git a/tvix/store/Cargo.toml b/tvix/store/Cargo.toml
index dece06be8fb4..3fabf4f84bd5 100644
--- a/tvix/store/Cargo.toml
+++ b/tvix/store/Cargo.toml
@@ -17,7 +17,7 @@ sha2 = "0.10.6"
 sled = { version = "0.34.7", features = ["compression"] }
 thiserror = "1.0.38"
 tokio-stream = "0.1.14"
-tokio = { version = "1.28.0", features = ["net", "rt-multi-thread", "signal"] }
+tokio = { version = "1.28.0", features = ["fs", "net", "rt-multi-thread", "signal"] }
 tonic = "0.8.2"
 tracing = "0.1.37"
 tracing-subscriber = { version = "0.3.16", features = ["json"] }
@@ -29,6 +29,7 @@ bytes = "1.4.0"
 smol_str = "0.2.0"
 serde_json = "1.0"
 url = "2.4.0"
+pin-project-lite = "0.2.13"
 
 [dependencies.fuser]
 optional = true