Add LimitStore (#2175) (apache#2242)

* Add LimitStore (#2175)

* Review feedback

* Fix test

Author: tustvold

src/aws.rs

@@ -684,6 +684,7 @@ impl AmazonS3Builder {
 
     /// Sets the maximum number of concurrent outstanding
     /// connectons. Default is `16`.
+    #[deprecated(note = "use LimitStore instead")]
     pub fn with_max_connections(mut self, max_connections: NonZeroUsize) -> Self {
         self.max_connections = max_connections;
         self

src/lib.rs

@@ -45,6 +45,7 @@ pub mod aws;
 pub mod azure;
 #[cfg(feature = "gcp")]
 pub mod gcp;
+pub mod limit;
 pub mod local;
 pub mod memory;
 pub mod path;

src/limit.rs

@@ -0,0 +1,263 @@
+// 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.
+
+//! An object store that limits the maximum concurrency of the wrapped implementation
+
+use crate::{
+    BoxStream, GetResult, ListResult, MultipartId, ObjectMeta, ObjectStore, Path, Result,
+    StreamExt,
+};
+use async_trait::async_trait;
+use bytes::Bytes;
+use futures::Stream;
+use std::io::{Error, IoSlice};
+use std::ops::Range;
+use std::pin::Pin;
+use std::sync::Arc;
+use std::task::{Context, Poll};
+use tokio::io::AsyncWrite;
+use tokio::sync::{OwnedSemaphorePermit, Semaphore};
+
+/// Store wrapper that wraps an inner store and limits the maximum number of concurrent
+/// object store operations. Where each call to an [`ObjectStore`] member function is
+/// considered a single operation, even if it may result in more than one network call
+///
+/// ```
+/// # use object_store::memory::InMemory;
+/// # use object_store::limit::LimitStore;
+///
+/// // Create an in-memory `ObjectStore` limited to 20 concurrent requests
+/// let store = LimitStore::new(InMemory::new(), 20);
+/// ```
+///
+#[derive(Debug)]
+pub struct LimitStore<T: ObjectStore> {
+    inner: T,
+    max_requests: usize,
+    semaphore: Arc<Semaphore>,
+}
+
+impl<T: ObjectStore> LimitStore<T> {
+    /// Create new limit store that will limit the maximum
+    /// number of outstanding concurrent requests to
+    /// `max_requests`
+    pub fn new(inner: T, max_requests: usize) -> Self {
+        Self {
+            inner,
+            max_requests,
+            semaphore: Arc::new(Semaphore::new(max_requests)),
+        }
+    }
+}
+
+impl<T: ObjectStore> std::fmt::Display for LimitStore<T> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "LimitStore({}, {})", self.max_requests, self.inner)
+    }
+}
+
+#[async_trait]
+impl<T: ObjectStore> ObjectStore for LimitStore<T> {
+    async fn put(&self, location: &Path, bytes: Bytes) -> Result<()> {
+        let _permit = self.semaphore.acquire().await.unwrap();
+        self.inner.put(location, bytes).await
+    }
+
+    async fn put_multipart(
+        &self,
+        location: &Path,
+    ) -> Result<(MultipartId, Box<dyn AsyncWrite + Unpin + Send>)> {
+        let permit = Arc::clone(&self.semaphore).acquire_owned().await.unwrap();
+        let (id, write) = self.inner.put_multipart(location).await?;
+        Ok((id, Box::new(PermitWrapper::new(write, permit))))
+    }
+
+    async fn abort_multipart(
+        &self,
+        location: &Path,
+        multipart_id: &MultipartId,
+    ) -> Result<()> {
+        let _permit = self.semaphore.acquire().await.unwrap();
+        self.inner.abort_multipart(location, multipart_id).await
+    }
+
+    async fn get(&self, location: &Path) -> Result<GetResult> {
+        let permit = Arc::clone(&self.semaphore).acquire_owned().await.unwrap();
+        match self.inner.get(location).await? {
+            r @ GetResult::File(_, _) => Ok(r),
+            GetResult::Stream(s) => {
+                Ok(GetResult::Stream(PermitWrapper::new(s, permit).boxed()))
+            }
+        }
+    }
+
+    async fn get_range(&self, location: &Path, range: Range<usize>) -> Result<Bytes> {
+        let _permit = self.semaphore.acquire().await.unwrap();
+        self.inner.get_range(location, range).await
+    }
+
+    async fn head(&self, location: &Path) -> Result<ObjectMeta> {
+        let _permit = self.semaphore.acquire().await.unwrap();
+        self.inner.head(location).await
+    }
+
+    async fn delete(&self, location: &Path) -> Result<()> {
+        let _permit = self.semaphore.acquire().await.unwrap();
+        self.inner.delete(location).await
+    }
+
+    async fn list(
+        &self,
+        prefix: Option<&Path>,
+    ) -> Result<BoxStream<'_, Result<ObjectMeta>>> {
+        let permit = Arc::clone(&self.semaphore).acquire_owned().await.unwrap();
+        let s = self.inner.list(prefix).await?;
+        Ok(PermitWrapper::new(s, permit).boxed())
+    }
+
+    async fn list_with_delimiter(&self, prefix: Option<&Path>) -> Result<ListResult> {
+        let _permit = self.semaphore.acquire().await.unwrap();
+        self.inner.list_with_delimiter(prefix).await
+    }
+
+    async fn copy(&self, from: &Path, to: &Path) -> Result<()> {
+        let _permit = self.semaphore.acquire().await.unwrap();
+        self.inner.copy(from, to).await
+    }
+
+    async fn rename(&self, from: &Path, to: &Path) -> Result<()> {
+        let _permit = self.semaphore.acquire().await.unwrap();
+        self.inner.rename(from, to).await
+    }
+
+    async fn copy_if_not_exists(&self, from: &Path, to: &Path) -> Result<()> {
+        let _permit = self.semaphore.acquire().await.unwrap();
+        self.inner.copy_if_not_exists(from, to).await
+    }
+
+    async fn rename_if_not_exists(&self, from: &Path, to: &Path) -> Result<()> {
+        let _permit = self.semaphore.acquire().await.unwrap();
+        self.inner.rename_if_not_exists(from, to).await
+    }
+}
+
+/// Combines an [`OwnedSemaphorePermit`] with some other type
+struct PermitWrapper<T> {
+    inner: T,
+    #[allow(dead_code)]
+    permit: OwnedSemaphorePermit,
+}
+
+impl<T> PermitWrapper<T> {
+    fn new(inner: T, permit: OwnedSemaphorePermit) -> Self {
+        Self { inner, permit }
+    }
+}
+
+impl<T: Stream + Unpin> Stream for PermitWrapper<T> {
+    type Item = T::Item;
+
+    fn poll_next(
+        mut self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+    ) -> Poll<Option<Self::Item>> {
+        Pin::new(&mut self.inner).poll_next(cx)
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.inner.size_hint()
+    }
+}
+
+impl<T: AsyncWrite + Unpin> AsyncWrite for PermitWrapper<T> {
+    fn poll_write(
+        mut self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+        buf: &[u8],
+    ) -> Poll<std::result::Result<usize, Error>> {
+        Pin::new(&mut self.inner).poll_write(cx, buf)
+    }
+
+    fn poll_flush(
+        mut self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+    ) -> Poll<std::result::Result<(), Error>> {
+        Pin::new(&mut self.inner).poll_flush(cx)
+    }
+
+    fn poll_shutdown(
+        mut self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+    ) -> Poll<std::result::Result<(), Error>> {
+        Pin::new(&mut self.inner).poll_shutdown(cx)
+    }
+
+    fn poll_write_vectored(
+        mut self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+        bufs: &[IoSlice<'_>],
+    ) -> Poll<std::result::Result<usize, Error>> {
+        Pin::new(&mut self.inner).poll_write_vectored(cx, bufs)
+    }
+
+    fn is_write_vectored(&self) -> bool {
+        self.inner.is_write_vectored()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::limit::LimitStore;
+    use crate::memory::InMemory;
+    use crate::tests::{
+        list_uses_directories_correctly, list_with_delimiter, put_get_delete_list,
+        rename_and_copy, stream_get,
+    };
+    use crate::ObjectStore;
+    use std::time::Duration;
+    use tokio::time::timeout;
+
+    #[tokio::test]
+    async fn limit_test() {
+        let max_requests = 10;
+        let memory = InMemory::new();
+        let integration = LimitStore::new(memory, max_requests);
+
+        put_get_delete_list(&integration).await.unwrap();
+        list_uses_directories_correctly(&integration).await.unwrap();
+        list_with_delimiter(&integration).await.unwrap();
+        rename_and_copy(&integration).await.unwrap();
+        stream_get(&integration).await.unwrap();
+
+        let mut streams = Vec::with_capacity(max_requests);
+        for _ in 0..max_requests {
+            let stream = integration.list(None).await.unwrap();
+            streams.push(stream);
+        }
+
+        let t = Duration::from_millis(20);
+
+        // Expect to not be able to make another request
+        assert!(timeout(t, integration.list(None)).await.is_err());
+
+        // Drop one of the streams
+        streams.pop();
+
+        // Can now make another request
+        integration.list(None).await.unwrap();
+    }
+}