use super::{BlobService, BlobWriter};
use crate::{proto, B3Digest};
use futures::sink::{SinkExt, SinkMapErr};
use std::{collections::VecDeque, io};
use tokio::task::JoinHandle;
use tokio_stream::{wrappers::ReceiverStream, StreamExt};
use tokio_util::{
io::{CopyToBytes, SinkWriter, SyncIoBridge},
sync::{PollSendError, PollSender},
};
use tonic::{transport::Channel, Code, Status, Streaming};
use tracing::instrument;
/// Connects to a (remote) tvix-store BlobService over gRPC.
#[derive(Clone)]
pub struct GRPCBlobService {
/// A handle into the active tokio runtime. Necessary to spawn tasks.
tokio_handle: tokio::runtime::Handle,
/// The internal reference to a gRPC client.
/// Cloning it is cheap, and it internally handles concurrent requests.
grpc_client: proto::blob_service_client::BlobServiceClient<Channel>,
}
// TODO: provide some contstructors
impl BlobService for GRPCBlobService {
type BlobReader = Box<dyn io::Read + Send>;
type BlobWriter = GRPCBlobWriter;
#[instrument(skip(self, digest), fields(blob.digest=%digest))]
fn has(&self, digest: &B3Digest) -> Result<bool, crate::Error> {
// Get a new handle to the gRPC client, and copy the digest.
let mut grpc_client = self.grpc_client.clone();
let digest = digest.clone();
let task: tokio::task::JoinHandle<Result<_, Status>> =
self.tokio_handle.spawn(async move {
Ok(grpc_client
.stat(proto::StatBlobRequest {
digest: digest.to_vec(),
..Default::default()
})
.await?
.into_inner())
});
match self.tokio_handle.block_on(task)? {
Ok(_blob_meta) => Ok(true),
Err(e) if e.code() == Code::NotFound => Ok(false),
Err(e) => Err(crate::Error::StorageError(e.to_string())),
}
}
// On success, this returns a Ok(Some(io::Read)), which can be used to read
// the contents of the Blob, identified by the digest.
fn open_read(&self, digest: &B3Digest) -> Result<Option<Self::BlobReader>, crate::Error> {
// Get a new handle to the gRPC client, and copy the digest.
let mut grpc_client = self.grpc_client.clone();
let digest = digest.clone();
// Construct the task that'll send out the request and return the stream
// the gRPC client should use to send [proto::BlobChunk], or an error if
// the blob doesn't exist.
let task: tokio::task::JoinHandle<Result<Streaming<proto::BlobChunk>, Status>> =
self.tokio_handle.spawn(async move {
let stream = grpc_client
.read(proto::ReadBlobRequest {
digest: digest.to_vec(),
})
.await?
.into_inner();
Ok(stream)
});
// This runs the task to completion, which on success will return a stream.
// On reading from it, we receive individual [proto::BlobChunk], so we
// massage this to a stream of bytes,
// then create an [AsyncRead], which we'll turn into a [io::Read],
// that's returned from the function.
match self.tokio_handle.block_on(task)? {
Ok(stream) => {
// map the stream of proto::BlobChunk to bytes.
let data_stream = stream.map(|x| {
x.map(|x| VecDeque::from(x.data))
.map_err(|e| std::io::Error::new(std::io::ErrorKind::InvalidInput, e))
});
// Use StreamReader::new to convert to an AsyncRead.
let data_reader = tokio_util::io::StreamReader::new(data_stream);
// Use SyncIoBridge to turn it into a sync Read.
let sync_reader = tokio_util::io::SyncIoBridge::new(data_reader);
Ok(Some(Box::new(sync_reader)))
}
Err(e) if e.code() == Code::NotFound => Ok(None),
Err(e) => Err(crate::Error::StorageError(e.to_string())),
}
}
/// Returns a [Self::BlobWriter], that'll internally wrap each write in a
// [proto::BlobChunk] and which is passed to the
fn open_write(&self) -> Result<Self::BlobWriter, crate::Error> {
let mut grpc_client = self.grpc_client.clone();
// set up an mpsc channel passing around Bytes.
let (tx, rx) = tokio::sync::mpsc::channel::<bytes::Bytes>(10);
// bytes arriving on the RX side are wrapped inside a
// [proto::BlobChunk], and a [ReceiverStream] is constructed.
let blobchunk_stream =
ReceiverStream::new(rx).map(|x| proto::BlobChunk { data: x.to_vec() });
// That receiver stream is used as a stream in the gRPC BlobService.put rpc call.
let task: tokio::task::JoinHandle<Result<_, Status>> = self
.tokio_handle
.spawn(async move { Ok(grpc_client.put(blobchunk_stream).await?.into_inner()) });
// The tx part of the channel is converted to a sink of byte chunks.
// We need to make this a function pointer, not a closure.
fn convert_error(_: PollSendError<bytes::Bytes>) -> io::Error {
io::Error::from(io::ErrorKind::BrokenPipe)
}
let sink = PollSender::new(tx)
.sink_map_err(convert_error as fn(PollSendError<bytes::Bytes>) -> io::Error);
// We need to explicitly cast here, otherwise rustc does error with "expected fn pointer, found fn item"
// … which is turned into an [tokio::io::AsyncWrite].
let async_writer = SinkWriter::new(CopyToBytes::new(sink));
// … which is then turned into a [io::Write].
let writer = SyncIoBridge::new(async_writer);
Ok(GRPCBlobWriter {
tokio_handle: self.tokio_handle.clone(), // TODO: is the clone() ok here?
task,
inner_writer: writer,
})
}
}
type BridgedWriter = SyncIoBridge<
SinkWriter<
CopyToBytes<
SinkMapErr<PollSender<bytes::Bytes>, fn(PollSendError<bytes::Bytes>) -> io::Error>,
>,
>,
>;
pub struct GRPCBlobWriter {
/// A handle into the active tokio runtime. Necessary to block on the task
/// containing the put request.
tokio_handle: tokio::runtime::Handle,
/// The task containing the put request.
task: JoinHandle<Result<proto::PutBlobResponse, Status>>,
/// The inner Writer.
inner_writer: BridgedWriter,
}
impl BlobWriter for GRPCBlobWriter {
fn close(mut self) -> Result<B3Digest, crate::Error> {
// invoke shutdown, so the inner writer closes its internal tx side of
// the channel.
self.inner_writer
.shutdown()
.map_err(|e| crate::Error::StorageError(e.to_string()))?;
// block on the RPC call to return.
// This ensures all chunks are sent out, and have been received by the
// backend.
match self.tokio_handle.block_on(self.task)? {
Ok(resp) => {
// return the digest from the response.
B3Digest::from_vec(resp.digest).map_err(|_| {
crate::Error::StorageError("invalid root digest length in response".to_string())
})
}
Err(e) => Err(crate::Error::StorageError(e.to_string())),
}
}
}
impl io::Write for GRPCBlobWriter {
fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
self.inner_writer.write(buf)
}
fn flush(&mut self) -> io::Result<()> {
self.inner_writer.flush()
}
}
