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Diffstat (limited to 'tvix/castore/src/import/blobs.rs')
| -rw-r--r-- | tvix/castore/src/import/blobs.rs | 190 |
1 files changed, 190 insertions, 0 deletions
diff --git a/tvix/castore/src/import/blobs.rs b/tvix/castore/src/import/blobs.rs new file mode 100644 index 000000000000..f71ee1e63768 --- /dev/null +++ b/tvix/castore/src/import/blobs.rs @@ -0,0 +1,190 @@ +use std::{ + io::{Cursor, Write}, + sync::Arc, +}; + +use tokio::{ + io::AsyncRead, + sync::Semaphore, + task::{JoinError, JoinSet}, +}; +use tokio_util::io::InspectReader; + +use crate::{blobservice::BlobService, B3Digest, Path, PathBuf}; + +/// Files smaller than this threshold, in bytes, are uploaded to the [BlobService] in the +/// background. +/// +/// This is a u32 since we acquire a weighted semaphore using the size of the blob. +/// [Semaphore::acquire_many_owned] takes a u32, so we need to ensure the size of +/// the blob can be represented using a u32 and will not cause an overflow. +const CONCURRENT_BLOB_UPLOAD_THRESHOLD: u32 = 1024 * 1024; + +/// The maximum amount of bytes allowed to be buffered in memory to perform async blob uploads. +const MAX_BUFFER_SIZE: usize = 128 * 1024 * 1024; + +#[derive(Debug, thiserror::Error)] +pub enum Error { + #[error("unable to read blob contents for {0}: {1}")] + BlobRead(PathBuf, std::io::Error), + + #[error("unable to check whether blob at {0} already exists: {1}")] + BlobCheck(PathBuf, std::io::Error), + + // FUTUREWORK: proper error for blob finalize + #[error("unable to finalize blob {0}: {1}")] + BlobFinalize(PathBuf, std::io::Error), + + #[error("unexpected size for {path} wanted: {wanted} got: {got}")] + UnexpectedSize { + path: PathBuf, + wanted: u64, + got: u64, + }, + + #[error("blob upload join error: {0}")] + JoinError(#[from] JoinError), +} + +/// The concurrent blob uploader provides a mechanism for concurrently uploading small blobs. +/// This is useful when ingesting from sources like tarballs and archives which each blob entry +/// must be read sequentially. Ingesting many small blobs sequentially becomes slow due to +/// round trip time with the blob service. The concurrent blob uploader will buffer small +/// blobs in memory and upload them to the blob service in the background. +/// +/// Once all blobs have been uploaded, make sure to call [ConcurrentBlobUploader::join] to wait +/// for all background jobs to complete and check for any errors. +pub struct ConcurrentBlobUploader<BS> { + blob_service: BS, + upload_tasks: JoinSet<Result<(), Error>>, + upload_semaphore: Arc<Semaphore>, +} + +impl<BS> ConcurrentBlobUploader<BS> +where + BS: BlobService + Clone + 'static, +{ + /// Creates a new concurrent blob uploader which uploads blobs to the provided + /// blob service. + pub fn new(blob_service: BS) -> Self { + Self { + blob_service, + upload_tasks: JoinSet::new(), + upload_semaphore: Arc::new(Semaphore::new(MAX_BUFFER_SIZE)), + } + } + + /// Uploads a blob to the blob service. If the blob is small enough it will be read to a buffer + /// and uploaded in the background. + /// This will read the entirety of the provided reader unless an error occurs, even if blobs + /// are uploaded in the background.. + pub async fn upload<R>( + &mut self, + path: &Path, + expected_size: u64, + mut r: R, + ) -> Result<B3Digest, Error> + where + R: AsyncRead + Unpin, + { + if expected_size < CONCURRENT_BLOB_UPLOAD_THRESHOLD as u64 { + let mut buffer = Vec::with_capacity(expected_size as usize); + let mut hasher = blake3::Hasher::new(); + let mut reader = InspectReader::new(&mut r, |bytes| { + hasher.write_all(bytes).unwrap(); + }); + + let permit = self + .upload_semaphore + .clone() + // This cast is safe because ensure the header_size is less than + // CONCURRENT_BLOB_UPLOAD_THRESHOLD which is a u32. + .acquire_many_owned(expected_size as u32) + .await + .unwrap(); + let size = tokio::io::copy(&mut reader, &mut buffer) + .await + .map_err(|e| Error::BlobRead(path.into(), e))?; + let digest: B3Digest = hasher.finalize().as_bytes().into(); + + if size != expected_size { + return Err(Error::UnexpectedSize { + path: path.into(), + wanted: expected_size, + got: size, + }); + } + + self.upload_tasks.spawn({ + let blob_service = self.blob_service.clone(); + let expected_digest = digest.clone(); + let path = path.to_owned(); + let r = Cursor::new(buffer); + async move { + // We know the blob digest already, check it exists before sending it. + if blob_service + .has(&expected_digest) + .await + .map_err(|e| Error::BlobCheck(path.clone(), e))? + { + drop(permit); + return Ok(()); + } + + let digest = upload_blob(&blob_service, &path, expected_size, r).await?; + + assert_eq!(digest, expected_digest, "Tvix bug: blob digest mismatch"); + + // Make sure we hold the permit until we finish writing the blob + // to the [BlobService]. + drop(permit); + Ok(()) + } + }); + + return Ok(digest); + } + + upload_blob(&self.blob_service, path, expected_size, r).await + } + + /// Waits for all background upload jobs to complete, returning any upload errors. + pub async fn join(mut self) -> Result<(), Error> { + while let Some(result) = self.upload_tasks.join_next().await { + result??; + } + Ok(()) + } +} + +async fn upload_blob<BS, R>( + blob_service: &BS, + path: &Path, + expected_size: u64, + mut r: R, +) -> Result<B3Digest, Error> +where + BS: BlobService, + R: AsyncRead + Unpin, +{ + let mut writer = blob_service.open_write().await; + + let size = tokio::io::copy(&mut r, &mut writer) + .await + .map_err(|e| Error::BlobRead(path.into(), e))?; + + let digest = writer + .close() + .await + .map_err(|e| Error::BlobFinalize(path.into(), e))?; + + if size != expected_size { + return Err(Error::UnexpectedSize { + path: path.into(), + wanted: expected_size, + got: size, + }); + } + + Ok(digest) +} |