Reduce the sizes of a number of streams & futures

CHANGELOG.md

@@ -1,3 +1,7 @@
+In Development
+--------------
+- Reduced the sizes of a number of streams & futures
+
 v0.4.0 (2024-07-09)
 -------------------
 - Set `Access-Control-Allow-Origin: *` header in all responses

Cargo.toml

@@ -16,10 +16,10 @@ publish = false
 
 [dependencies]
 anyhow = "1.0.86"
-async-stream = "0.3.5"
 async-trait = "0.1.81"
 aws-config = { version = "1.5.3", features = ["behavior-version-latest"] }
 aws-sdk-s3 = "1.39.0"
+aws-smithy-async = "1.2.1"
 aws-smithy-runtime-api = "1.7.1"
 aws-smithy-types-convert = { version = "0.60.8", features = ["convert-time"] }
 axum = { version = "0.7.5", default-features = false, features = ["http1", "tokio", "tower-log"] }
@@ -33,6 +33,7 @@ itertools = "0.13.0"
 memory-stats = "1.2.0"
 moka = { version = "0.12.8", features = ["future"] }
 percent-encoding = "2.3.1"
+pin-project-lite = "0.2.14"
 reqwest = { version = "0.12.5", default-features = false, features = ["json", "rustls-tls-native-roots"] }
 reqwest-middleware = "0.3.2"
 reqwest-retry = "0.6.0"

src/dandi/mod.rs

@@ -1,7 +1,9 @@
 mod dandiset_id;
+mod streams;
 mod types;
 mod version_id;
 pub(crate) use self::dandiset_id::*;
+use self::streams::Paginate;
 pub(crate) use self::types::*;
 pub(crate) use self::version_id::*;
 use crate::consts::S3CLIENT_CACHE_SIZE;
@@ -10,7 +12,6 @@
 use crate::s3::{
     BucketSpec, GetBucketRegionError, PrefixedS3Client, S3Client, S3Error, S3Location,
 };
-use async_stream::try_stream;
 use futures_util::{Stream, TryStreamExt};
 use moka::future::{Cache, CacheBuilder};
 use serde::de::DeserializeOwned;
@@ -51,20 +52,8 @@
         self.inner.get_json(url).await.map_err(Into::into)
     }
 
-    fn paginate<T: DeserializeOwned + 'static>(
-        &self,
-        url: Url,
-    ) -> impl Stream<Item = Result<T, DandiError>> + '_ {
-        try_stream! {
-            let mut url = Some(url);
-            while let Some(u) = url {
-                let page = self.inner.get_json::<Page<T>>(u).await?;
-                for r in page.results {
-                    yield r;
-                }
-                url = page.next;
-            }
-        }
+    fn paginate<T: DeserializeOwned + 'static>(&self, url: Url) -> Paginate<T> {
+        Paginate::new(self, url)
     }
 
     async fn get_s3client(&self, loc: S3Location) -> Result<PrefixedS3Client, ZarrToS3Error> {
@@ -247,35 +236,26 @@
     pub(crate) fn get_root_children(
         &self,
     ) -> impl Stream<Item = Result<DandiResource, DandiError>> + '_ {
-        try_stream! {
-            let stream = self.get_entries_under_path(None);
-            tokio::pin!(stream);
-            while let Some(entry) = stream.try_next().await? {
+        self.get_entries_under_path(None)
+            .and_then(move |entry| async move {
                 match entry {
-                    FolderEntry::Folder(subf) => yield DandiResource::Folder(subf),
+                    FolderEntry::Folder(subf) => Ok(DandiResource::Folder(subf)),
                     FolderEntry::Asset { id, path } => match self.get_asset_by_id(&id).await {
-                        Ok(asset) => yield DandiResource::Asset(asset),
+                        Ok(asset) => Ok(DandiResource::Asset(asset)),
                         Err(DandiError::Http(HttpError::NotFound { .. })) => {
-                            Err(DandiError::DisappearingAsset { asset_id: id, path })?;
+                            Err(DandiError::DisappearingAsset { asset_id: id, path })
                         }
-                        Err(e) => Err(e)?,
+                        Err(e) => Err(e),
                     },
                 }
-            }
-        }
+            })
     }
 
-    fn get_folder_entries(
-        &self,
-        path: &AssetFolder,
-    ) -> impl Stream<Item = Result<FolderEntry, DandiError>> + '_ {
+    fn get_folder_entries(&self, path: &AssetFolder) -> Paginate<FolderEntry> {
         self.get_entries_under_path(Some(&path.path))
     }
 
-    fn get_entries_under_path(
-        &self,
-        path: Option<&PureDirPath>,
-    ) -> impl Stream<Item = Result<FolderEntry, DandiError>> + '_ {
+    fn get_entries_under_path(&self, path: Option<&PureDirPath>) -> Paginate<FolderEntry> {
         let mut url = self.client.get_url([
             "dandisets",
             self.dandiset_id.as_ref(),
@@ -304,8 +284,7 @@
             .append_pair("metadata", "1")
             .append_pair("order", "path");
         let dirpath = path.to_dir_path();
-        let stream = self.client.paginate::<RawAsset>(url.clone());
-        tokio::pin!(stream);
+        let mut stream = self.client.paginate::<RawAsset>(url.clone());
         while let Some(asset) = stream.try_next().await? {
             if &asset.path == path {
                 return Ok(AtAssetPath::Asset(asset.try_into_asset(self)?));
@@ -371,8 +350,7 @@
         match self.get_resource_with_s3(path).await? {
             DandiResourceWithS3::Folder(folder) => {
                 let mut children = Vec::new();
-                let stream = self.get_folder_entries(&folder);
-                tokio::pin!(stream);
+                let mut stream = self.get_folder_entries(&folder);
                 while let Some(child) = stream.try_next().await? {
                     let child = match child {
                         FolderEntry::Folder(subf) => DandiResource::Folder(subf),
@@ -391,25 +369,19 @@
             DandiResourceWithS3::Asset(Asset::Blob(r)) => Ok(DandiResourceWithChildren::Blob(r)),
             DandiResourceWithS3::Asset(Asset::Zarr(zarr)) => {
                 let s3 = self.client.get_s3client_for_zarr(&zarr).await?;
-                let mut children = Vec::new();
-                {
-                    let stream = s3.get_root_entries();
-                    tokio::pin!(stream);
-                    while let Some(child) = stream.try_next().await? {
-                        children.push(zarr.make_resource(child));
-                    }
-                }
+                let children = s3
+                    .get_root_entries()
+                    .map_ok(|child| zarr.make_resource(child))
+                    .try_collect::<Vec<_>>()
+                    .await?;
                 Ok(DandiResourceWithChildren::Zarr { zarr, children })
             }
             DandiResourceWithS3::ZarrFolder { folder, s3 } => {
-                let mut children = Vec::new();
-                {
-                    let stream = s3.get_folder_entries(&folder.path);
-                    tokio::pin!(stream);
-                    while let Some(child) = stream.try_next().await? {
-                        children.push(folder.make_resource(child));
-                    }
-                }
+                let children = s3
+                    .get_folder_entries(&folder.path)
+                    .map_ok(|child| folder.make_resource(child))
+                    .try_collect::<Vec<_>>()
+                    .await?;
                 Ok(DandiResourceWithChildren::ZarrFolder { folder, children })
             }
             DandiResourceWithS3::ZarrEntry(r) => Ok(DandiResourceWithChildren::ZarrEntry(r)),

src/dandi/streams.rs

@@ -0,0 +1,82 @@
+use super::types::Page;
+use super::{DandiClient, DandiError};
+use crate::httputil::{Client, HttpError};
+use futures_util::{future::BoxFuture, FutureExt, Stream};
+use pin_project_lite::pin_project;
+use serde::de::DeserializeOwned;
+use std::pin::Pin;
+use std::task::{ready, Context, Poll};
+use url::Url;
+
+pin_project! {
+    // Implementing paginate() as a manually-implemented Stream instead of via
+    // async_stream lets us save about 4700 bytes on dandidav's top-level
+    // Futures.
+    #[must_use = "streams do nothing unless polled"]
+    pub(super) struct Paginate<T> {
+        client: Client,
+        state: PaginateState<T>,
+    }
+}
+
+enum PaginateState<T> {
+    Requesting(BoxFuture<'static, Result<Page<T>, HttpError>>),
+    Yielding {
+        results: std::vec::IntoIter<T>,
+        next: Option<Url>,
+    },
+    Done,
+}
+
+impl<T> Paginate<T> {
+    pub(super) fn new(client: &DandiClient, url: Url) -> Self {
+        Paginate {
+            client: client.inner.clone(),
+            state: PaginateState::Yielding {
+                results: Vec::new().into_iter(),
+                next: Some(url),
+            },
+        }
+    }
+}
+
+impl<T> Stream for Paginate<T>
+where
+    T: DeserializeOwned + 'static,
+{
+    type Item = Result<T, DandiError>;
+
+    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        let this = self.project();
+        loop {
+            match this.state {
+                PaginateState::Requesting(ref mut fut) => match ready!(fut.as_mut().poll(cx)) {
+                    Ok(page) => {
+                        *this.state = PaginateState::Yielding {
+                            results: page.results.into_iter(),
+                            next: page.next,
+                        }
+                    }
+                    Err(e) => {
+                        *this.state = PaginateState::Done;
+                        return Some(Err(DandiError::from(e))).into();
+                    }
+                },
+                PaginateState::Yielding {
+                    ref mut results,
+                    ref mut next,
+                } => {
+                    if let Some(item) = results.next() {
+                        return Some(Ok(item)).into();
+                    } else if let Some(url) = next.take() {
+                        *this.state =
+                            PaginateState::Requesting(this.client.get_json::<Page<T>>(url).boxed());
+                    } else {
+                        *this.state = PaginateState::Done;
+                    }
+                }
+                PaginateState::Done => return None.into(),
+            }
+        }
+    }
+}

src/dav/mod.rs

@@ -43,8 +43,7 @@
         &self,
         req: Request<Body>,
     ) -> Result<Response<Body>, Infallible> {
-        // Box large future:
-        let resp = match Box::pin(self.inner_handle_request(req)).await {
+        let resp = match self.inner_handle_request(req).await {
             Ok(r) => r,
             Err(e) if e.is_404() => {
                 let e = anyhow::Error::from(e);
@@ -246,12 +245,12 @@
             DavPath::Root => Ok(DavResourceWithChildren::root()),
             DavPath::DandisetIndex => {
                 let col = DavCollection::dandiset_index();
-                let mut children = Vec::new();
-                let stream = self.dandi.get_all_dandisets();
-                tokio::pin!(stream);
-                while let Some(ds) = stream.try_next().await? {
-                    children.push(DavResource::Collection(ds.into()));
-                }
+                let children = self
+                    .dandi
+                    .get_all_dandisets()
+                    .map_ok(|ds| DavResource::Collection(ds.into()))
+                    .try_collect::<Vec<_>>()
+                    .await?;
                 Ok(DavResourceWithChildren::Collection { col, children })
             }
             DavPath::Dandiset { dandiset_id } => {
@@ -282,8 +281,7 @@
                 let col = DavCollection::dandiset_releases(dandiset_id);
                 let mut children = Vec::new();
                 let endpoint = self.dandi.dandiset(dandiset_id.clone());
-                let stream = endpoint.get_all_versions();
-                tokio::pin!(stream);
+                let mut stream = endpoint.get_all_versions();
                 while let Some(v) = stream.try_next().await? {
                     if let VersionId::Published(ref pvid) = v.version {
                         let path = version_path(dandiset_id, &VersionSpec::Published(pvid.clone()));
@@ -299,12 +297,11 @@
                 version,
             } => {
                 let (col, endpoint) = self.get_dandiset_version(dandiset_id, version).await?;
-                let mut children = Vec::new();
-                let stream = endpoint.get_root_children();
-                tokio::pin!(stream);
-                while let Some(res) = stream.try_next().await? {
-                    children.push(DavResource::from(res).under_version_path(dandiset_id, version));
-                }
+                let mut children = endpoint
+                    .get_root_children()
+                    .map_ok(|res| DavResource::from(res).under_version_path(dandiset_id, version))
+                    .try_collect::<Vec<_>>()
+                    .await?;
                 children.push(
                     self.get_dandiset_yaml(dandiset_id, version)
                         .await

src/httputil.rs

@@ -3,6 +3,7 @@
 use reqwest_middleware::{Middleware, Next};
 use reqwest_retry::{policies::ExponentialBackoff, RetryTransientMiddleware};
 use serde::de::DeserializeOwned;
+use std::future::Future;
 use thiserror::Error;
 use tracing::Instrument;
 use url::Url;
@@ -53,12 +54,23 @@
         self.request(Method::GET, url).await
     }
 
-    pub(crate) async fn get_json<T: DeserializeOwned>(&self, url: Url) -> Result<T, HttpError> {
-        self.get(url.clone())
-            .await?
-            .json::<T>()
-            .await
-            .map_err(move |source| HttpError::Deserialize { url, source })
+    pub(crate) fn get_json<T: DeserializeOwned>(
+        &self,
+        url: Url,
+    ) -> impl Future<Output = Result<T, HttpError>> {
+        // Clone the client and move it into an async block (as opposed to just
+        // writing a "normal" async function) so that the resulting Future will
+        // be 'static rather than retaining a reference to &self, thereby
+        // facilitating the Future's use by the Paginate stream.
+        let client = self.clone();
+        async move {
+            client
+                .get(url.clone())
+                .await?
+                .json::<T>()
+                .await
+                .map_err(move |source| HttpError::Deserialize { url, source })
+        }
     }
 }