diff --git a/services/backup/src/blob/get_client.rs b/services/backup/src/blob/downloader.rs similarity index 90% rename from services/backup/src/blob/get_client.rs rename to services/backup/src/blob/downloader.rs index a82d1b9d4..4079ff925 100644 --- a/services/backup/src/blob/get_client.rs +++ b/services/backup/src/blob/downloader.rs @@ -1,82 +1,82 @@ use anyhow::{bail, Result}; use tokio::{ sync::mpsc::{self, Receiver}, task::JoinHandle, }; use tracing::{instrument, Instrument}; use super::proto; use crate::constants::MPSC_CHANNEL_BUFFER_CAPACITY; pub use proto::put_request::Data as PutRequestData; pub use proto::{PutRequest, PutResponse}; -/// The GetClient instance is a handle holder of a Tokio task running the +/// The BlobDownloader instance is a handle holder of a Tokio task running the /// actual blob client instance. The communication is done via a MPSC channel /// and is one-sided - the data is transmitted from the client task to the /// caller. Blob chunks received in response stream are waiting /// for the channel to have capacity, so it is recommended to read them quickly /// to make room for more. /// The client task can be stopped and awaited for result via the `terminate()` /// method. -pub struct GetClient { +pub struct BlobDownloader { rx: Receiver>, handle: JoinHandle>, } -impl GetClient { +impl BlobDownloader { /// Connects to the Blob service and keeps the client connection open /// in a separate Tokio task. - #[instrument(name = "get_client")] + #[instrument(name = "blob_downloader")] pub async fn start(holder: String) -> Result { let service_url = &crate::CONFIG.blob_service_url; let mut blob_client = proto::blob_service_client::BlobServiceClient::connect( service_url.to_string(), ) .await?; let (blob_res_tx, blob_res_rx) = mpsc::channel(MPSC_CHANNEL_BUFFER_CAPACITY); let client_thread = async move { let response = blob_client.get(proto::GetRequest { holder }).await?; let mut inner_response = response.into_inner(); loop { match inner_response.message().await? { Some(data) => { let data: Vec = data.data_chunk; if let Err(err) = blob_res_tx.send(data).await { bail!(err); } } // Response stream was closed None => break, } } Ok(()) }; let handle = tokio::spawn(client_thread.in_current_span()); - Ok(GetClient { + Ok(BlobDownloader { rx: blob_res_rx, handle, }) } /// Receives the next chunk of blob data if ready or sleeps /// until the data is available. /// /// Returns `None` when the transmission is finished, but this doesn't /// determine if it was successful. After receiving `None`, the client /// should be consumed by calling [`GetClient::terminate`] to handle /// possible errors. - pub async fn get(&mut self) -> Option> { + pub async fn next_chunk(&mut self) -> Option> { self.rx.recv().await } /// Stops receiving messages and awaits the client thread to exit /// and returns its status. pub async fn terminate(mut self) -> Result<()> { self.rx.close(); self.handle.await? } } diff --git a/services/backup/src/blob/mod.rs b/services/backup/src/blob/mod.rs index f20dca0e2..a0e3e4d3d 100644 --- a/services/backup/src/blob/mod.rs +++ b/services/backup/src/blob/mod.rs @@ -1,10 +1,10 @@ mod proto { tonic::include_proto!("blob"); } pub use proto::put_request::Data as PutRequestData; pub use proto::{PutRequest, PutResponse}; -mod get_client; +mod downloader; mod put_client; -pub use get_client::*; +pub use downloader::*; pub use put_client::*; diff --git a/services/backup/src/service/handlers/pull_backup.rs b/services/backup/src/service/handlers/pull_backup.rs index e20c30ca6..10e645360 100644 --- a/services/backup/src/service/handlers/pull_backup.rs +++ b/services/backup/src/service/handlers/pull_backup.rs @@ -1,328 +1,328 @@ use async_stream::try_stream; use tokio_stream::{Stream, StreamExt}; use tonic::Status; use tracing::{debug, error, trace, warn}; use tracing_futures::Instrument; use super::handle_db_error; use super::proto::{self, PullBackupResponse}; use crate::{ - blob::GetClient, + blob::BlobDownloader, constants::{ BACKUP_TABLE_FIELD_ATTACHMENT_HOLDERS, BACKUP_TABLE_FIELD_BACKUP_ID, GRPC_CHUNK_SIZE_LIMIT, GRPC_METADATA_SIZE_PER_MESSAGE, LOG_TABLE_FIELD_ATTACHMENT_HOLDERS, LOG_TABLE_FIELD_LOG_ID, }, database::{BackupItem, DatabaseClient, LogItem}, }; pub struct PullBackupHandler { backup_item: BackupItem, logs: Vec, } impl PullBackupHandler { pub async fn new( db: &DatabaseClient, request: proto::PullBackupRequest, ) -> Result { let proto::PullBackupRequest { user_id, backup_id } = request; let backup_item = db .find_backup_item(&user_id, &backup_id) .await .map_err(handle_db_error)? .ok_or_else(|| { debug!("Backup item not found"); Status::not_found("Backup item not found") })?; let backup_id = backup_item.backup_id.as_str(); let logs = db .find_log_items_for_backup(backup_id) .await .map_err(handle_db_error)?; Ok(PullBackupHandler { backup_item, logs }) } /// Consumes the handler and provides a response `Stream`. The stream will /// produce the following in order: /// - Backup compaction data chunks /// - Backup logs /// - Whole log, if stored in db /// - Log chunks, if stored in blob pub fn into_response_stream( self, ) -> impl Stream> { use proto::pull_backup_response::*; try_stream! { debug!("Pulling backup..."); { let compaction_stream = data_stream(&self.backup_item); tokio::pin!(compaction_stream); while let Some(response) = compaction_stream.try_next().await? { yield response; } } trace!("Backup data pull complete."); if self.logs.is_empty() { debug!("No logs to pull. Finishing"); return; } debug!("Pulling logs..."); for log in self.logs { trace!("Pulling log ID={}", &log.log_id); let span = tracing::trace_span!("log", log_id = &log.log_id); if log.persisted_in_blob { trace!(parent: &span, "Log persisted in blob"); let log_data_stream = data_stream(&log).instrument(span); tokio::pin!(log_data_stream); while let Some(response) = log_data_stream.try_next().await? { yield response; } } else { trace!(parent: &span, "Log persisted in database"); yield proto::PullBackupResponse { attachment_holders: Some(log.attachment_holders), id: Some(Id::LogId(log.log_id)), data: Some(Data::LogChunk(log.value.into_bytes())), }; } } trace!("Pulled all logs, done"); } } } /// Downloads a blob-stored [`BlobStoredItem`] and streams its content into /// stream of [`PullBackupResponse`] objects, handles gRPC message size details. fn data_stream( item: &Item, ) -> impl Stream> + '_ where Item: BlobStoredItem, { try_stream! { let mut buffer = ResponseBuffer::default(); - let mut client = - GetClient::start(item.get_holder().to_string()).await.map_err(|err| { + let mut downloader = + BlobDownloader::start(item.get_holder().to_string()).await.map_err(|err| { error!( - "Failed to start blob client: {:?}", err + "Failed to start blob downloader: {:?}", err ); Status::aborted("Internal error") })?; let mut is_first_chunk = true; loop { if !buffer.is_saturated() { - if let Some(data) = client.get().await { + if let Some(data) = downloader.next_chunk().await { buffer.put(data); } } if buffer.is_empty() { break; } // get data chunk, shortened by length of metadata let padding = item.metadata_size(is_first_chunk); let chunk = buffer.get_chunk(padding); trace!( with_attachments = is_first_chunk, data_size = chunk.len(), "Sending data chunk" ); yield item.to_response(chunk, is_first_chunk); is_first_chunk = false; } - client.terminate().await.map_err(|err| { - error!("Blob client failed: {:?}", err); + downloader.terminate().await.map_err(|err| { + error!("Blob downloader failed: {:?}", err); Status::aborted("Internal error") })?; } } /// Represents downloadable item stored in Blob service trait BlobStoredItem { // Blob holder representing this item fn get_holder(&self) -> &str; /// Generates a gRPC response for given `data_chunk`. /// The response may be in extended version, with `include_extra_info`, /// ususally sent with first chunk fn to_response( &self, data_chunk: Vec, include_extra_info: bool, ) -> proto::PullBackupResponse; /// Size in bytes of non-data fields contained in response message. fn metadata_size(&self, include_extra_info: bool) -> usize; } impl BlobStoredItem for BackupItem { fn get_holder(&self) -> &str { &self.compaction_holder } fn to_response( &self, data_chunk: Vec, include_extra_info: bool, ) -> proto::PullBackupResponse { use proto::pull_backup_response::*; let attachment_holders = if include_extra_info { Some(self.attachment_holders.clone()) } else { None }; proto::PullBackupResponse { id: Some(Id::BackupId(self.backup_id.clone())), data: Some(Data::CompactionChunk(data_chunk)), attachment_holders, } } fn metadata_size(&self, include_extra_info: bool) -> usize { let mut extra_bytes: usize = 0; extra_bytes += BACKUP_TABLE_FIELD_BACKUP_ID.as_bytes().len(); extra_bytes += self.backup_id.as_bytes().len(); if include_extra_info { extra_bytes += BACKUP_TABLE_FIELD_ATTACHMENT_HOLDERS.as_bytes().len(); extra_bytes += self.attachment_holders.as_bytes().len(); } extra_bytes } } impl BlobStoredItem for LogItem { fn get_holder(&self) -> &str { &self.value } fn to_response( &self, data_chunk: Vec, include_extra_info: bool, ) -> proto::PullBackupResponse { use proto::pull_backup_response::*; let attachment_holders = if include_extra_info { Some(self.attachment_holders.clone()) } else { None }; proto::PullBackupResponse { id: Some(Id::LogId(self.log_id.clone())), data: Some(Data::LogChunk(data_chunk)), attachment_holders, } } fn metadata_size(&self, include_extra_info: bool) -> usize { let mut extra_bytes: usize = 0; extra_bytes += LOG_TABLE_FIELD_LOG_ID.as_bytes().len(); extra_bytes += self.log_id.as_bytes().len(); if include_extra_info { extra_bytes += LOG_TABLE_FIELD_ATTACHMENT_HOLDERS.as_bytes().len(); extra_bytes += self.attachment_holders.as_bytes().len(); } extra_bytes } } /// A utility structure that buffers downloaded data and allows to retrieve it /// as chunks of arbitrary size, not greater than provided `limit`. struct ResponseBuffer { buf: Vec, limit: usize, } impl Default for ResponseBuffer { /// Buffer size defaults to max usable gRPC message size fn default() -> Self { ResponseBuffer::new(GRPC_CHUNK_SIZE_LIMIT - GRPC_METADATA_SIZE_PER_MESSAGE) } } impl ResponseBuffer { pub fn new(limit: usize) -> Self { ResponseBuffer { buf: Vec::new(), limit, } } pub fn put(&mut self, data: Vec) { if data.len() > self.limit { warn!("Data saved to buffer is larger than chunk limit."); } self.buf.extend(data); } /// Gets chunk of size `limit - padding` and leaves remainder in buffer pub fn get_chunk(&mut self, padding: usize) -> Vec { let mut chunk = std::mem::take(&mut self.buf); let target_size = self.limit - padding; if chunk.len() > target_size { // after this operation, chunk=0..target_size, self.buf=target_size..end self.buf = chunk.split_off(target_size); } return chunk; } /// Does buffer length exceed given limit pub fn is_saturated(&self) -> bool { self.buf.len() >= self.limit } pub fn is_empty(&self) -> bool { self.buf.is_empty() } } #[cfg(test)] mod tests { use super::*; const LIMIT: usize = 100; #[test] fn test_response_buffer() { let mut buffer = ResponseBuffer::new(LIMIT); assert_eq!(buffer.is_empty(), true); // put 80 bytes of data buffer.put(vec![0u8; 80]); assert_eq!(buffer.is_empty(), false); assert_eq!(buffer.is_saturated(), false); // put next 80 bytes, should be saturated as 160 > 100 buffer.put(vec![0u8; 80]); let buf_size = buffer.buf.len(); assert_eq!(buffer.is_saturated(), true); assert_eq!(buf_size, 160); // get one chunk let padding: usize = 10; let expected_chunk_size = LIMIT - padding; let chunk = buffer.get_chunk(padding); assert_eq!(chunk.len(), expected_chunk_size); // 90 // buffer should not be saturated now (160 - 90 < 100) let remaining_buf_size = buffer.buf.len(); assert_eq!(remaining_buf_size, buf_size - expected_chunk_size); assert_eq!(buffer.is_saturated(), false); // get last chunk let chunk = buffer.get_chunk(padding); assert_eq!(chunk.len(), remaining_buf_size); assert_eq!(buffer.is_empty(), true); } }