Add retries for Python downloads (#9274)

## Summary

This uses the same approach as in the rest of uv, but with another
dedicated method for retries.

Closes https://github.com/astral-sh/uv/issues/8525.

crates/uv-python/Cargo.toml

@@ -45,6 +45,7 @@ owo-colors = { workspace = true }
 regex = { workspace = true }
 reqwest = { workspace = true }
 reqwest-middleware = { workspace = true }
+reqwest-retry = { workspace = true }
 rmp-serde = { workspace = true }
 same-file = { workspace = true }
 schemars = { workspace = true, optional = true }

crates/uv-python/src/downloads.rs

@@ -1,18 +1,22 @@
-use futures::TryStreamExt;
-use owo_colors::OwoColorize;
 use std::fmt::Display;
 use std::io;
 use std::path::{Path, PathBuf};
 use std::pin::Pin;
 use std::str::FromStr;
 use std::task::{Context, Poll};
+use std::time::{Duration, SystemTime};
+
+use futures::TryStreamExt;
+use owo_colors::OwoColorize;
+use reqwest_retry::RetryPolicy;
 use thiserror::Error;
 use tokio::io::{AsyncRead, ReadBuf};
 use tokio_util::compat::FuturesAsyncReadCompatExt;
 use tokio_util::either::Either;
 use tracing::{debug, instrument};
 use url::Url;
-use uv_client::WrappedReqwestError;
+
+use uv_client::{is_extended_transient_error, WrappedReqwestError};
 use uv_distribution_filename::{ExtensionError, SourceDistExtension};
 use uv_extract::hash::Hasher;
 use uv_fs::{rename_with_retry, Simplified};
@@ -417,6 +421,7 @@ impl FromStr for PythonDownloadRequest {
 
 include!("downloads.inc");
 
+#[derive(Debug, Clone)]
 pub enum DownloadResult {
     AlreadyAvailable(PathBuf),
     Fetched(PathBuf),
@@ -458,7 +463,57 @@ impl ManagedPythonDownload {
         self.sha256
     }
 
-    /// Download and extract
+    /// Download and extract a Python distribution, retrying on failure.
+    #[instrument(skip(client, installation_dir, cache_dir, reporter), fields(download = % self.key()))]
+    pub async fn fetch_with_retry(
+        &self,
+        client: &uv_client::BaseClient,
+        installation_dir: &Path,
+        cache_dir: &Path,
+        reinstall: bool,
+        python_install_mirror: Option<&str>,
+        pypy_install_mirror: Option<&str>,
+        reporter: Option<&dyn Reporter>,
+    ) -> Result<DownloadResult, Error> {
+        let mut n_past_retries = 0;
+        let start_time = SystemTime::now();
+        let retry_policy = client.retry_policy();
+        loop {
+            let result = self
+                .fetch(
+                    client,
+                    installation_dir,
+                    cache_dir,
+                    reinstall,
+                    python_install_mirror,
+                    pypy_install_mirror,
+                    reporter,
+                )
+                .await;
+            if result
+                .as_ref()
+                .err()
+                .is_some_and(|err| is_extended_transient_error(err))
+            {
+                let retry_decision = retry_policy.should_retry(start_time, n_past_retries);
+                if let reqwest_retry::RetryDecision::Retry { execute_after } = retry_decision {
+                    debug!(
+                        "Transient failure while handling response for {}; retrying...",
+                        self.key()
+                    );
+                    let duration = execute_after
+                        .duration_since(SystemTime::now())
+                        .unwrap_or_else(|_| Duration::default());
+                    tokio::time::sleep(duration).await;
+                    n_past_retries += 1;
+                    continue;
+                }
+            }
+            return result;
+        }
+    }
+
+    /// Download and extract a Python distribution.
     #[instrument(skip(client, installation_dir, cache_dir, reporter), fields(download = % self.key()))]
     pub async fn fetch(
         &self,
@@ -466,8 +521,8 @@ impl ManagedPythonDownload {
         installation_dir: &Path,
         cache_dir: &Path,
         reinstall: bool,
-        python_install_mirror: Option<String>,
-        pypy_install_mirror: Option<String>,
+        python_install_mirror: Option<&str>,
+        pypy_install_mirror: Option<&str>,
         reporter: Option<&dyn Reporter>,
     ) -> Result<DownloadResult, Error> {
         let url = self.download_url(python_install_mirror, pypy_install_mirror)?;
@@ -492,7 +547,7 @@ impl ManagedPythonDownload {
 
         debug!(
             "Downloading {url} to temporary location: {}",
-            temp_dir.path().simplified().display()
+            temp_dir.path().simplified_display()
         );
 
         let mut hashers = self
@@ -589,8 +644,8 @@ impl ManagedPythonDownload {
     /// appropriate environment variable, use it instead.
     fn download_url(
         &self,
-        python_install_mirror: Option<String>,
-        pypy_install_mirror: Option<String>,
+        python_install_mirror: Option<&str>,
+        pypy_install_mirror: Option<&str>,
     ) -> Result<Url, Error> {
         match self.key.implementation {
             LenientImplementationName::Known(ImplementationName::CPython) => {

crates/uv-python/src/installation.rs

@@ -86,8 +86,8 @@ impl PythonInstallation {
         client_builder: &BaseClientBuilder<'a>,
         cache: &Cache,
         reporter: Option<&dyn Reporter>,
-        python_install_mirror: Option<String>,
-        pypy_install_mirror: Option<String>,
+        python_install_mirror: Option<&str>,
+        pypy_install_mirror: Option<&str>,
     ) -> Result<Self, Error> {
         let request = request.unwrap_or_else(|| &PythonRequest::Default);
 
@@ -132,8 +132,8 @@ impl PythonInstallation {
         client_builder: &BaseClientBuilder<'a>,
         cache: &Cache,
         reporter: Option<&dyn Reporter>,
-        python_install_mirror: Option<String>,
-        pypy_install_mirror: Option<String>,
+        python_install_mirror: Option<&str>,
+        pypy_install_mirror: Option<&str>,
     ) -> Result<Self, Error> {
         let installations = ManagedPythonInstallations::from_settings()?.init()?;
         let installations_dir = installations.root();
@@ -145,7 +145,7 @@ impl PythonInstallation {
 
         info!("Fetching requested Python...");
         let result = download
-            .fetch(
+            .fetch_with_retry(
                 &client,
                 installations_dir,
                 &cache_dir,