fix: concurrent downloads, ref #322

ort-sys/build.rs

@@ -1,5 +1,5 @@
 use std::{
-	env, fs,
+	env, fs, io,
 	path::{Path, PathBuf}
 };
 
@@ -16,9 +16,9 @@ const ORT_EXTRACT_DIR: &str = "onnxruntime";
 
 const DIST_TABLE: &str = include_str!("dist.txt");
 
-#[path = "src/internal/dirs.rs"]
-mod dirs;
-use self::dirs::cache_dir;
+#[path = "src/internal/mod.rs"]
+mod internal;
+use self::internal::dirs::cache_dir;
 
 #[cfg(feature = "download-binaries")]
 fn fetch_file(source_url: &str) -> Vec<u8> {
@@ -450,20 +450,38 @@ fn prepare_libort_dir() -> (PathBuf, bool) {
 
 			let (prebuilt_url, prebuilt_hash) = dist.unwrap();
 
-			let mut cache_dir = cache_dir()
+			let bin_extract_dir = cache_dir()
 				.expect("could not determine cache directory")
 				.join("dfbin")
 				.join(target)
 				.join(prebuilt_hash);
-			if fs::create_dir_all(&cache_dir).is_err() {
-				cache_dir = env::var("OUT_DIR").unwrap().into();
-			}
 
-			let lib_dir = cache_dir.join(ORT_EXTRACT_DIR);
+			let lib_dir = bin_extract_dir.join(ORT_EXTRACT_DIR);
 			if !lib_dir.exists() {
 				let downloaded_file = fetch_file(prebuilt_url);
 				assert!(verify_file(&downloaded_file, prebuilt_hash), "hash of downloaded ONNX Runtime binary does not match!");
-				extract_tgz(&downloaded_file, &cache_dir);
+
+				let mut temp_extract_dir = bin_extract_dir
+					.parent()
+					.unwrap()
+					.join(format!("tmp.{}_{prebuilt_hash}", self::internal::random_identifier()));
+				let mut should_rename = true;
+				if fs::create_dir_all(&temp_extract_dir).is_err() {
+					temp_extract_dir = env::var("OUT_DIR").unwrap().into();
+					should_rename = false;
+				}
+				extract_tgz(&downloaded_file, &temp_extract_dir);
+				if should_rename {
+					match std::fs::rename(&temp_extract_dir, bin_extract_dir) {
+						Ok(()) => {}
+						Err(e) => match e.kind() {
+							io::ErrorKind::AlreadyExists | io::ErrorKind::DirectoryNotEmpty => {
+								let _ = fs::remove_dir_all(temp_extract_dir);
+							}
+							_ => panic!("failed to extract downloaded binaries: {e}")
+						}
+					}
+				}
 			}
 
 			static_link_prerequisites(true);

ort-sys/src/internal/mod.rs

@@ -1 +1,16 @@
+use std::hash::{BuildHasher, Hasher, RandomState};
+
 pub mod dirs;
+
+pub fn random_identifier() -> String {
+	let mut state = RandomState::new().build_hasher().finish();
+	std::iter::repeat_with(move || {
+		state ^= state << 13;
+		state ^= state >> 7;
+		state ^= state << 17;
+		state
+	})
+	.take(12)
+	.map(|i| b"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"[i as usize % 62] as char)
+	.collect()
+}

src/session/builder/impl_commit.rs

@@ -30,7 +30,7 @@ impl SessionBuilder {
 			let _ = write!(&mut s, "{:02x}", b);
 			s
 		});
-		let model_filepath = download_dir.join(model_filename);
+		let model_filepath = download_dir.join(&model_filename);
 		let downloaded_path = if model_filepath.exists() {
 			tracing::info!(model_filepath = format!("{}", model_filepath.display()).as_str(), "Model already exists, skipping download");
 			model_filepath
@@ -46,16 +46,28 @@ impl SessionBuilder {
 			tracing::info!(len, "Downloading {} bytes", len);
 
 			let mut reader = resp.into_reader();
+			let temp_filepath = download_dir.join(format!("tmp_{}.{model_filename}", ort_sys::internal::random_identifier()));
 
-			let f = std::fs::File::create(&model_filepath).expect("Failed to create model file");
+			let f = std::fs::File::create(&temp_filepath).expect("Failed to create model file");
 			let mut writer = std::io::BufWriter::new(f);
 
 			let bytes_io_count = std::io::copy(&mut reader, &mut writer).map_err(Error::wrap)?;
-			if bytes_io_count == len as u64 {
-				model_filepath
-			} else {
+			if bytes_io_count != len as u64 {
 				return Err(Error::new(format!("Failed to download entire model; file only has {bytes_io_count} bytes, expected {len}")));
 			}
+
+			drop(writer);
+
+			match std::fs::rename(&temp_filepath, &model_filepath) {
+				Ok(()) => model_filepath,
+				Err(e) => match e.kind() {
+					std::io::ErrorKind::AlreadyExists => {
+						let _ = std::fs::remove_file(temp_filepath);
+						model_filepath
+					}
+					_ => return Err(Error::new(format!("Failed to download model: {e}")))
+				}
+			}
 		};
 
 		self.commit_from_file(downloaded_path)