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docs(tvix/castore/blobsvc): fix doc comments on trait

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The readers implement AsyncRead/AsyncSeek, not their sync counterparts.
Also update expectations around chunks.

Change-Id: Ic266688039d80d16d33f651b96ce2bcdedecfa00
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10734
Autosubmit: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
Reviewed-by: Connor Brewster <cbrewster@hey.com>
This commit is contained in:
Florian Klink 2024-02-02 17:36:22 +02:00 committed by clbot
parent 5f0f4ea374
commit 1157eea710
1 changed files with 14 additions and 10 deletions
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24
tvix/castore/src/blobservice/mod.rs
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@ -24,19 +24,22 @@ pub use self::sled::SledBlobService;
/// The base trait all BlobService services need to implement.
/// It provides functions to check whether a given blob exists,
/// a way to get a [io::Read] to a blob, and a method to initiate writing a new
/// Blob, which will return something implmenting io::Write, and providing a
/// close funtion, to finalize a blob and get its digest.
/// a way to read (and seek) a blob, and a method to create a blobwriter handle,
/// which will implement a writer interface, and also provides a close funtion,
/// to finalize a blob and get its digest.
#[async_trait]
pub trait BlobService: Send + Sync {
/// Check if the service has the blob, by its content hash.
/// On implementations returning chunks, this must also work for chunks.
async fn has(&self, digest: &B3Digest) -> io::Result<bool>;
/// Request a blob from the store, by its content hash.
/// On implementations returning chunks, this must also work for chunks.
async fn open_read(&self, digest: &B3Digest) -> io::Result<Option<Box<dyn BlobReader>>>;
/// Insert a new blob into the store. Returns a [BlobWriter], which
/// implements [io::Write] and a [BlobWriter::close].
/// implements [tokio::io::AsyncWrite] and a [BlobWriter::close] to finalize
/// the blob and get its digest.
async fn open_write(&self) -> Box<dyn BlobWriter>;
/// Return a list of chunks for a given blob.
@ -44,20 +47,21 @@ pub trait BlobService: Send + Sync {
/// The former return value is sent in case the blob is not present at all,
/// while the second one is sent in case there's no more granular chunks (or
/// the backend does not support chunking).
/// A default implementation signalling the backend does not support
/// chunking is provided.
/// A default implementation checking for existence and then returning it
/// does not have more granular chunks available is provided.
async fn chunks(&self, digest: &B3Digest) -> io::Result<Option<Vec<ChunkMeta>>> {
if !self.has(digest).await? {
return Ok(None);
} else {
// default implementation, signalling the backend does not support chunking.
// default implementation, signalling the backend does not have more
// granular chunks available.
return Ok(Some(vec![]));
}
}
}
/// A [tokio::io::AsyncWrite] that you need to close() afterwards, and get back
/// the digest of the written blob.
/// A [tokio::io::AsyncWrite] that the user needs to close() afterwards for persist.
/// On success, it returns the digest of the written blob.
#[async_trait]
pub trait BlobWriter: tokio::io::AsyncWrite + Send + Sync + Unpin + 'static {
/// Signal there's no more data to be written, and return the digest of the
@ -67,7 +71,7 @@ pub trait BlobWriter: tokio::io::AsyncWrite + Send + Sync + Unpin + 'static {
async fn close(&mut self) -> io::Result<B3Digest>;
}
/// A [tokio::io::AsyncRead] that also allows seeking.
/// BlobReader is a [tokio::io::AsyncRead] that also allows seeking.
pub trait BlobReader: tokio::io::AsyncRead + tokio::io::AsyncSeek + Send + Unpin + 'static {}
/// A [`io::Cursor<Vec<u8>>`] can be used as a BlobReader.