crepererum commented on code in PR #5500: URL: https://github.com/apache/arrow-rs/pull/5500#discussion_r1526180783
########## object_store/src/upload.rs: ########## @@ -0,0 +1,151 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you under the Apache License, Version 2.0 (the +// "License"); you may not use this file except in compliance +// with the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, +// software distributed under the License is distributed on an +// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +// KIND, either express or implied. See the License for the +// specific language governing permissions and limitations +// under the License. + +use crate::{PutResult, Result}; +use async_trait::async_trait; +use bytes::Bytes; +use futures::future::BoxFuture; +use tokio::task::JoinSet; + +/// An upload part request +pub type UploadPart = BoxFuture<'static, Result<()>>; + +#[async_trait] +pub trait Upload: Send + std::fmt::Debug { + /// Upload the next part + /// + /// Returns a stream + /// + /// Most stores require that all parts excluding the last are at least 5 MiB, and some + /// further require that all parts excluding the last be the same size, e.g. [R2]. + /// Clients wanting to maximise compatibility should therefore perform writes in + /// fixed size blocks larger than 5 MiB. + /// + /// Implementations may invoke this method multiple times and then await on the + /// returned futures in parallel + /// + /// ```no_run + /// # use futures::StreamExt; + /// # use object_store::Upload; + /// # + /// # async fn test() { + /// # + /// let mut upload: Box<&dyn Upload> = todo!(); + /// let mut p1 = upload.put_part(vec![0; 10 * 1024 * 1024].into()); + /// let mut p2 = upload.put_part(vec![1; 10 * 1024 * 1024].into()); + /// + /// let (u1, u2) = futures::future::join(p1.next(), p2.next()).await; + /// u1.unwrap().unwrap(); + /// u2.unwrap().unwrap(); + /// let result = upload.complete().await.unwrap(); + /// # } + /// ``` + /// + /// [R2]: https://developers.cloudflare.com/r2/objects/multipart-objects/#limitations + fn put_part(&mut self, data: Bytes) -> UploadPart; Review Comment: > Instead by taking a mutable borrow and providing the `data` to be written, we prohibit out of order writes. The final piece is we return a `BoxFuture<'static, Result<()>>` instead of this being an `async fn`, i.e. returning `BoxFuture<'_, Result<()>>`. This allows multiple `UploadPart` to be created and polled in parallel, without the borrow checker complaining about concurrent mutable borrows. I think this should be part of the docstring for future reference. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
