tustvold commented on code in PR #375: URL: https://github.com/apache/arrow-rs-object-store/pull/375#discussion_r2094185142
########## src/registry.rs: ########## @@ -0,0 +1,238 @@ +// 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. + +//! Map object URLs to [`ObjectStore`] + +use crate::path::{InvalidPart, Path, PathPart}; +use crate::{parse_url, parse_url_opts, ObjectStore}; +use parking_lot::RwLock; +use std::borrow::Borrow; +use std::collections::btree_map::Entry; +use std::collections::{BTreeMap, Bound}; +use std::sync::Arc; +use url::Url; + +/// Error type for [`ObjectStoreRegistry`] +#[derive(Debug, thiserror::Error)] +#[non_exhaustive] +enum Error { + #[error("ObjectStore not found")] + NotFound, + + #[error("Error parsing URL path segment")] + InvalidPart(#[from] InvalidPart), +} + +impl From<Error> for crate::Error { + fn from(value: Error) -> Self { + Self::Generic { + store: "ObjectStoreRegistry", + source: Box::new(value), + } + } +} + +/// [`ObjectStoreRegistry`] maps a URL to an [`ObjectStore`] instance +pub trait ObjectStoreRegistry: Send + Sync + std::fmt::Debug + 'static { + /// Register a new store for the provided store URL + /// + /// If a store with the same URL existed before, it is replaced and returned + fn register(&self, url: Url, store: Arc<dyn ObjectStore>) -> Option<Arc<dyn ObjectStore>>; + + /// Unregister a store for the provided store URL + fn unregister(&self, url: &Url) -> Option<Arc<dyn ObjectStore>>; + + /// Resolve an object URL + /// + /// If [`ObjectStoreRegistry::register`] has been called with a URL with the same + /// scheme and host as the object URL, and a path that is a prefix of the object URL's + /// it should be returned with along with the trailing path. In the event of multiple + /// possibilities the longest path match should be returned. + /// + /// If a store hasn't been registered, [`ObjectStoreRegistry`] may lazily create + /// one if the URL is understood, or return an [`Error::NotFound`] + /// + /// For example + /// + /// ``` + /// # use std::sync::Arc; + /// # use url::Url; + /// # use object_store::memory::InMemory; + /// # use object_store::ObjectStore; + /// # use object_store::prefix::PrefixStore; + /// # use object_store::registry::{DefaultObjectStoreRegistry, ObjectStoreRegistry}; + /// # + /// let registry = DefaultObjectStoreRegistry::new(); + /// + /// let bucket1 = Arc::new(InMemory::new()) as Arc<dyn ObjectStore>; + /// let base = Url::parse("s3://bucket1/").unwrap(); + /// registry.register(base, bucket1.clone()); + /// + /// let url = Url::parse("s3://bucket1/path/to/object").unwrap(); + /// let (ret, path) = registry.resolve(&url).unwrap(); + /// assert_eq!(path.as_ref(), "path/to/object"); + /// assert!(Arc::ptr_eq(&ret, &bucket1)); + /// + /// let bucket2 = Arc::new(InMemory::new()) as Arc<dyn ObjectStore>; + /// let base = Url::parse("https://s3.region.amazonaws.com/bucket";).unwrap(); + /// registry.register(base, bucket2.clone()); + /// + /// let url = Url::parse("https://s3.region.amazonaws.com/bucket/path/to/object";).unwrap(); + /// let (ret, path) = registry.resolve(&url).unwrap(); + /// assert_eq!(path.as_ref(), "path/to/object"); + /// assert!(Arc::ptr_eq(&ret, &bucket2)); + /// + /// let bucket3 = Arc::new(PrefixStore::new(InMemory::new(), "path")) as Arc<dyn ObjectStore>; + /// let base = Url::parse("https://s3.region.amazonaws.com/bucket/path";).unwrap(); + /// registry.register(base, bucket3.clone()); + /// + /// let url = Url::parse("https://s3.region.amazonaws.com/bucket/path/to/object";).unwrap(); + /// let (ret, path) = registry.resolve(&url).unwrap(); + /// assert_eq!(path.as_ref(), "to/object"); + /// assert!(Arc::ptr_eq(&ret, &bucket3)); + /// ``` + fn resolve(&self, url: &Url) -> crate::Result<(Arc<dyn ObjectStore>, Path)>; +} + +/// An [`ObjectStoreRegistry`] that uses [`parse_url`] to create stores based on the environment +#[derive(Debug, Default)] +pub struct DefaultObjectStoreRegistry { + map: RwLock<BTreeMap<StrUrl, RegistryEntry>>, +} + +/// Wrapper around [`Url`] implementing `Borrow<str>` +#[derive(Debug, Ord, PartialOrd, Eq, PartialEq)] +struct StrUrl(Url); + +impl Borrow<str> for StrUrl { + fn borrow(&self) -> &str { + self.0.as_str() + } +} + +#[derive(Debug)] +struct RegistryEntry { + store: Arc<dyn ObjectStore>, + /// The number of non-empty path segments in the store's URL + path_segments: usize, +} + +impl RegistryEntry { + fn new(url: &Url, store: Arc<dyn ObjectStore>) -> Self { + let path_segments = match url.path() { + "/" => 0, + path => path.as_bytes().iter().filter(|&&c| c == b'/').count(), + }; + Self { + path_segments, + store, + } + } + + fn resolve(&self, url: &Url) -> Result<(Arc<dyn ObjectStore>, Path), Error> { + let segments = match url.path_segments() { + Some(segments) => segments.skip(self.path_segments), + None => return Ok((self.store.clone(), Path::default())), + }; + + let path = segments.map(PathPart::parse).collect::<Result<_, _>>()?; + Ok((self.store.clone(), path)) + } +} + +impl DefaultObjectStoreRegistry { + /// Create a new [`DefaultObjectStoreRegistry`] + pub fn new() -> Self { + Self::default() + } +} + +impl ObjectStoreRegistry for DefaultObjectStoreRegistry { + fn register(&self, url: Url, store: Arc<dyn ObjectStore>) -> Option<Arc<dyn ObjectStore>> { + let entry = RegistryEntry::new(&url, store); + Some(self.map.write().insert(StrUrl(url), entry)?.store) + } + + fn unregister(&self, store: &Url) -> Option<Arc<dyn ObjectStore>> { + Some(self.map.write().remove(store.as_str())?.store) + } + + fn resolve(&self, url: &Url) -> crate::Result<(Arc<dyn ObjectStore>, Path)> { + { + let map = self.map.read(); + let start = Bound::Included(&url[..url::Position::BeforePath]); + + let longest = map Review Comment: This is the downside of this formulation, we have to use a BTreeMap which is slower than a HashMap, and if there are multiple (scheme, host) matches we have to scan through them -- This is an automated message from the Apache Git Service. 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