use std::{
io::{self, Cursor},
pin::pin,
sync::Arc,
task::Poll,
};
use data_encoding::HEXLOWER;
use fastcdc::v2020::AsyncStreamCDC;
use futures::Future;
use object_store::{path::Path, ObjectStore};
use pin_project_lite::pin_project;
use prost::Message;
use tokio::io::{AsyncRead, AsyncWrite, AsyncWriteExt};
use tokio_stream::StreamExt;
use tonic::async_trait;
use tracing::{debug, instrument, trace, Level};
use url::Url;
use crate::{
proto::{stat_blob_response::ChunkMeta, StatBlobResponse},
B3Digest, B3HashingReader,
};
use super::{BlobReader, BlobService, BlobWriter, ChunkedReader};
#[derive(Clone)]
pub struct ObjectStoreBlobService {
object_store: Arc<dyn ObjectStore>,
base_path: Path,
/// Average chunk size for FastCDC, in bytes.
/// min value is half, max value double of that number.
avg_chunk_size: u32,
}
/// Uses any object storage supported by the [object_store] crate to provide a
/// tvix-castore [BlobService].
///
/// # Data format
/// Data is organized in "blobs" and "chunks".
/// Blobs don't hold the actual data, but instead contain a list of more
/// granular chunks that assemble to the contents requested.
/// This allows clients to seek, and not download chunks they already have
/// locally, as it's referred to from other files.
/// Check `rpc_blobstore` and more general BlobStore docs on that.
///
/// ## Blobs
/// Stored at `${base_path}/blobs/b3/$digest_key`. They contains the serialized
/// StatBlobResponse for the blob with the digest.
///
/// ## Chunks
/// Chunks are stored at `${base_path}/chunks/b3/$digest_key`. They contain
/// the literal contents of the chunk, but are zstd-compressed.
///
/// ## Digest key sharding
/// The blake3 digest encoded in lower hex, and sharded after the second
/// character.
/// The blob for "Hello World" is stored at
/// `${base_path}/blobs/b3/41/41f8394111eb713a22165c46c90ab8f0fd9399c92028fd6d288944b23ff5bf76`.
///
/// This reduces the number of files in the same directory, which would be a
/// problem at least when using [object_store::local::LocalFileSystem].
///
/// # Future changes
/// There's no guarantees about this being a final format yet.
/// Once object_store gets support for additional metadata / content-types,
/// we can eliminate some requests (small blobs only consisting of a single
/// chunk can be stored as-is, without the blob index file).
/// It also allows signalling any compression of chunks in the content-type.
/// Migration *should* be possible by simply adding the right content-types to
/// all keys stored so far, but no promises ;-)
impl ObjectStoreBlobService {
/// Constructs a new [ObjectStoreBlobService] from a [Url] supported by
/// [object_store].
/// Any path suffix becomes the base path of the object store.
/// additional options, the same as in [object_store::parse_url_opts] can
/// be passed.
pub fn parse_url_opts<I, K, V>(url: &Url, options: I) -> Result<Self, object_store::Error>
where
I: IntoIterator<Item = (K, V)>,
K: AsRef<str>,
V: Into<String>,
{
let (object_store, path) = object_store::parse_url_opts(url, options)?;
Ok(Self {
object_store: Arc::new(object_store),
base_path: path,
avg_chunk_size: 256 * 1024,
})
}
/// Like [Self::parse_url_opts], except without the options.
pub fn parse_url(url: &Url) -> Result<Self, object_store::Error> {
Self::parse_url_opts(url, Vec::<(String, String)>::new())
}
}
#[instrument(level=Level::TRACE, skip_all,fields(base_path=%base_path,blob.digest=%digest),ret(Display))]
fn derive_blob_path(base_path: &Path, digest: &B3Digest) -> Path {
base_path
.child("blobs")
.child("b3")
.child(HEXLOWER.encode(&digest.as_slice()[..2]))
.child(HEXLOWER.encode(digest.as_slice()))
}
#[instrument(level=Level::TRACE, skip_all,fields(base_path=%base_path,chunk.digest=%digest),ret(Display))]
fn derive_chunk_path(base_path: &Path, digest: &B3Digest) -> Path {
base_path
.child("chunks")
.child("b3")
.child(HEXLOWER.encode(&digest.as_slice()[..2]))
.child(HEXLOWER.encode(digest.as_slice()))
}
#[async_trait]
impl BlobService for ObjectStoreBlobService {
#[instrument(skip_all, ret, err, fields(blob.digest=%digest))]
async fn has(&self, digest: &B3Digest) -> io::Result<bool> {
// TODO: clarify if this should work for chunks or not, and explicitly
// document in the proto docs.
let p = derive_blob_path(&self.base_path, digest);
match self.object_store.head(&p).await {
Ok(_) => Ok(true),
Err(object_store::Error::NotFound { .. }) => {
let p = derive_chunk_path(&self.base_path, digest);
match self.object_store.head(&p).await {
Ok(_) => Ok(true),
Err(object_store::Error::NotFound { .. }) => Ok(false),
Err(e) => Err(e)?,
}
}
Err(e) => Err(e)?,
}
}
#[instrument(skip_all, err, fields(blob.digest=%digest))]
async fn open_read(&self, digest: &B3Digest) -> io::Result<Option<Box<dyn BlobReader>>> {
// handle reading the empty blob.
if digest.as_slice() == blake3::hash(b"").as_bytes() {
return Ok(Some(Box::new(Cursor::new(b"")) as Box<dyn BlobReader>));
}
match self
.object_store
.get(&derive_chunk_path(&self.base_path, digest))
.await
{
Ok(res) => {
// handle reading blobs that are small enough to fit inside a single chunk:
// fetch the entire chunk into memory, decompress, ensure the b3 digest matches,
// and return a io::Cursor over that data.
// FUTUREWORK: use zstd::bulk to prevent decompression bombs
let chunk_raw_bytes = res.bytes().await?;
let chunk_contents = zstd::stream::decode_all(Cursor::new(chunk_raw_bytes))?;
if *digest != blake3::hash(&chunk_contents).as_bytes().into() {
Err(io::Error::other("chunk contents invalid"))?;
}
Ok(Some(Box::new(Cursor::new(chunk_contents))))
}
Err(object_store::Error::NotFound { .. }) => {
// NOTE: For public-facing things, we would want to stop here.
// Clients should fetch granularly, so they can make use of
// chunks they have locally.
// However, if this is used directly, without any caches, do the
// assembly here.
// This is subject to change, once we have store composition.
// TODO: make this configurable, and/or clarify behaviour for
// the gRPC server surface (explicitly document behaviour in the
// proto docs)
if let Some(chunks) = self.chunks(digest).await? {
let chunked_reader = ChunkedReader::from_chunks(
chunks.into_iter().map(|chunk| {
(
chunk.digest.try_into().expect("invalid b3 digest"),
chunk.size,
)
}),
Arc::new(self.clone()) as Arc<dyn BlobService>,
);
Ok(Some(Box::new(chunked_reader)))
} else {
// This is neither a chunk nor a blob, return None.
Ok(None)
}
}
Err(e) => Err(e.into()),
}
}
#[instrument(skip_all)]
async fn open_write(&self) -> Box<dyn BlobWriter> {
// ObjectStoreBlobWriter implements AsyncWrite, but all the chunking
// needs an AsyncRead, so we create a pipe here.
// In its `AsyncWrite` implementation, `ObjectStoreBlobWriter` delegates
// writes to w. It periodically polls the future that's reading from the
// other side.
let (w, r) = tokio::io::duplex(self.avg_chunk_size as usize * 10);
Box::new(ObjectStoreBlobWriter {
writer: Some(w),
fut: Some(Box::pin(chunk_and_upload(
r,
self.object_store.clone(),
self.base_path.clone(),
self.avg_chunk_size / 2,
self.avg_chunk_size,
self.avg_chunk_size * 2,
))),
fut_output: None,
})
}
#[instrument(skip_all, err, fields(blob.digest=%digest))]
async fn chunks(&self, digest: &B3Digest) -> io::Result<Option<Vec<ChunkMeta>>> {
match self
.object_store
.get(&derive_blob_path(&self.base_path, digest))
.await
{
Ok(get_result) => {
// fetch the data at the blob path
let blob_data = get_result.bytes().await?;
// parse into StatBlobResponse
let stat_blob_response: StatBlobResponse = StatBlobResponse::decode(blob_data)?;
debug!(
chunk.count = stat_blob_response.chunks.len(),
blob.size = stat_blob_response
.chunks
.iter()
.map(|x| x.size)
.sum::<u64>(),
"found more granular chunks"
);
Ok(Some(stat_blob_response.chunks))
}
Err(object_store::Error::NotFound { .. }) => {
// If there's only a chunk, we must return the empty vec here, rather than None.
match self
.object_store
.head(&derive_chunk_path(&self.base_path, digest))
.await
{
Ok(_) => {
// present, but no more chunks available
debug!("found a single chunk");
Ok(Some(vec![]))
}
Err(object_store::Error::NotFound { .. }) => {
// Neither blob nor single chunk found
debug!("not found");
Ok(None)
}
// error checking for chunk
Err(e) => Err(e.into()),
}
}
// error checking for blob
Err(err) => Err(err.into()),
}
}
}
/// Reads blob contents from a AsyncRead, chunks and uploads them.
/// On success, returns a [StatBlobResponse] pointing to the individual chunks.
#[instrument(skip_all, fields(base_path=%base_path, min_chunk_size, avg_chunk_size, max_chunk_size), err)]
async fn chunk_and_upload<R: AsyncRead + Unpin>(
r: R,
object_store: Arc<dyn ObjectStore>,
base_path: Path,
min_chunk_size: u32,
avg_chunk_size: u32,
max_chunk_size: u32,
) -> io::Result<B3Digest> {
// wrap reader with something calculating the blake3 hash of all data read.
let mut b3_r = B3HashingReader::from(r);
// set up a fastcdc chunker
let mut chunker =
AsyncStreamCDC::new(&mut b3_r, min_chunk_size, avg_chunk_size, max_chunk_size);
/// This really should just belong into the closure at
/// `chunker.as_stream().then(|_| { … })``, but if we try to, rustc spits
/// higher-ranked lifetime errors at us.
async fn fastcdc_chunk_uploader(
resp: Result<fastcdc::v2020::ChunkData, fastcdc::v2020::Error>,
base_path: Path,
object_store: Arc<dyn ObjectStore>,
) -> std::io::Result<ChunkMeta> {
let chunk_data = resp?;
let chunk_digest: B3Digest = blake3::hash(&chunk_data.data).as_bytes().into();
let chunk_path = derive_chunk_path(&base_path, &chunk_digest);
upload_chunk(object_store, chunk_digest, chunk_path, chunk_data.data).await
}
// Use the fastcdc chunker to produce a stream of chunks, and upload these
// that don't exist to the backend.
let chunks = chunker
.as_stream()
.then(|resp| fastcdc_chunk_uploader(resp, base_path.clone(), object_store.clone()))
.collect::<io::Result<Vec<ChunkMeta>>>()
.await?;
let stat_blob_response = StatBlobResponse {
chunks,
bao: "".into(), // still todo
};
// check for Blob, if it doesn't exist, persist.
let blob_digest: B3Digest = b3_r.digest().into();
let blob_path = derive_blob_path(&base_path, &blob_digest);
match object_store.head(&blob_path).await {
// blob already exists, nothing to do
Ok(_) => {
trace!(
blob.digest = %blob_digest,
blob.path = %blob_path,
"blob already exists on backend"
);
}
// chunk does not yet exist, upload first
Err(object_store::Error::NotFound { .. }) => {
debug!(
blob.digest = %blob_digest,
blob.path = %blob_path,
"uploading blob"
);
object_store
.put(&blob_path, stat_blob_response.encode_to_vec().into())
.await?;
}
Err(err) => {
// other error
Err(err)?
}
}
Ok(blob_digest)
}
/// upload chunk if it doesn't exist yet.
#[instrument(skip_all, fields(chunk.digest = %chunk_digest, chunk.size = chunk_data.len(), chunk.path = %chunk_path), err)]
async fn upload_chunk(
object_store: Arc<dyn ObjectStore>,
chunk_digest: B3Digest,
chunk_path: Path,
chunk_data: Vec<u8>,
) -> std::io::Result<ChunkMeta> {
let chunk_size = chunk_data.len();
match object_store.head(&chunk_path).await {
// chunk already exists, nothing to do
Ok(_) => {
debug!("chunk already exists");
}
// chunk does not yet exist, compress and upload.
Err(object_store::Error::NotFound { .. }) => {
let chunk_data_compressed =
zstd::encode_all(Cursor::new(chunk_data), zstd::DEFAULT_COMPRESSION_LEVEL)?;
debug!(chunk.compressed_size=%chunk_data_compressed.len(), "uploading chunk");
object_store
.as_ref()
.put(&chunk_path, chunk_data_compressed.into())
.await?;
}
// other error
Err(err) => Err(err)?,
}
Ok(ChunkMeta {
digest: chunk_digest.into(),
size: chunk_size as u64,
})
}
pin_project! {
/// Takes care of blob uploads.
/// All writes are relayed to self.writer, and we continuously poll the
/// future (which will internally read from the other side of the pipe and
/// upload chunks).
/// Our BlobWriter::close() needs to drop self.writer, so the other side
/// will read EOF and can finalize the blob.
/// The future should then resolve and return the blob digest.
pub struct ObjectStoreBlobWriter<W, Fut>
where
W: AsyncWrite,
Fut: Future,
{
#[pin]
writer: Option<W>,
#[pin]
fut: Option<Fut>,
fut_output: Option<io::Result<B3Digest>>
}
}
impl<W, Fut> tokio::io::AsyncWrite for ObjectStoreBlobWriter<W, Fut>
where
W: AsyncWrite + Send + Unpin,
Fut: Future,
{
fn poll_write(
self: std::pin::Pin<&mut Self>,
cx: &mut std::task::Context<'_>,
buf: &[u8],
) -> std::task::Poll<Result<usize, io::Error>> {
let this = self.project();
// poll the future.
let fut = this.fut.as_pin_mut().expect("not future");
let fut_p = fut.poll(cx);
// if it's ready, the only way this could have happened is that the
// upload failed, because we're only closing `self.writer` after all
// writes happened.
if fut_p.is_ready() {
return Poll::Ready(Err(io::Error::other("upload failed")));
}
// write to the underlying writer
this.writer
.as_pin_mut()
.expect("writer must be some")
.poll_write(cx, buf)
}
fn poll_flush(
self: std::pin::Pin<&mut Self>,
cx: &mut std::task::Context<'_>,
) -> std::task::Poll<Result<(), io::Error>> {
let this = self.project();
// poll the future.
let fut = this.fut.as_pin_mut().expect("not future");
let fut_p = fut.poll(cx);
// if it's ready, the only way this could have happened is that the
// upload failed, because we're only closing `self.writer` after all
// writes happened.
if fut_p.is_ready() {
return Poll::Ready(Err(io::Error::other("upload failed")));
}
// Call poll_flush on the writer
this.writer
.as_pin_mut()
.expect("writer must be some")
.poll_flush(cx)
}
fn poll_shutdown(
self: std::pin::Pin<&mut Self>,
_cx: &mut std::task::Context<'_>,
) -> std::task::Poll<Result<(), io::Error>> {
// There's nothing to do on shutdown. We might have written some chunks
// that are nowhere else referenced, but cleaning them up here would be racy.
std::task::Poll::Ready(Ok(()))
}
}
#[async_trait]
impl<W, Fut> BlobWriter for ObjectStoreBlobWriter<W, Fut>
where
W: AsyncWrite + Send + Unpin,
Fut: Future<Output = io::Result<B3Digest>> + Send + Unpin,
{
async fn close(&mut self) -> io::Result<B3Digest> {
match self.writer.take() {
Some(mut writer) => {
// shut down the writer, so the other side will read EOF.
writer.shutdown().await?;
// take out the future.
let fut = self.fut.take().expect("fut must be some");
// await it.
let resp = pin!(fut).await;
match resp.as_ref() {
// In the case of an Ok value, we store it in self.fut_output,
// so future calls to close can return that.
Ok(b3_digest) => {
self.fut_output = Some(Ok(b3_digest.clone()));
}
Err(e) => {
// for the error type, we need to cheat a bit, as
// they're not clone-able.
// Simply store a sloppy clone, with the same ErrorKind and message there.
self.fut_output = Some(Err(std::io::Error::new(e.kind(), e.to_string())))
}
}
resp
}
None => {
// called a second time, return self.fut_output.
match self.fut_output.as_ref().unwrap() {
Ok(ref b3_digest) => Ok(b3_digest.clone()),
Err(e) => Err(std::io::Error::new(e.kind(), e.to_string())),
}
}
}
}
}
#[cfg(test)]
mod test {
use super::chunk_and_upload;
use crate::{
blobservice::{BlobService, ObjectStoreBlobService},
fixtures::{BLOB_A, BLOB_A_DIGEST},
};
use std::{io::Cursor, sync::Arc};
use url::Url;
/// Tests chunk_and_upload directly, bypassing the BlobWriter at open_write().
#[tokio::test]
async fn test_chunk_and_upload() {
let blobsvc = Arc::new(
ObjectStoreBlobService::parse_url(&Url::parse("memory:///").unwrap()).unwrap(),
);
let blob_digest = chunk_and_upload(
&mut Cursor::new(BLOB_A.to_vec()),
blobsvc.object_store.clone(),
object_store::path::Path::from("/"),
1024 / 2,
1024,
1024 * 2,
)
.await
.expect("chunk_and_upload succeeds");
assert_eq!(BLOB_A_DIGEST.clone(), blob_digest);
// Now we should have the blob
assert!(blobsvc.has(&BLOB_A_DIGEST).await.unwrap());
}
}
