Fetch car times sequentially to respect the API's provisioned throughput

src/parsing/mod.rs

@@ -362,11 +362,15 @@ pub async fn parse_all_times(
 /// Remote URL for the per-car timing API.
 const CAR_TIMING_API_BASE: &str = "https://api.topdrivesrecords.com/car/";
 
-/// Fetches timing data files for all cars using controlled concurrency.
+/// Fetches timing data files for all cars sequentially.
+///
+/// The records API is a hobbyist backend backed by a provisioned-throughput
+/// database; concurrent fetching outruns its read capacity and produces HTTP
+/// 400 "provisioned throughput exceeded" errors, so downloads are issued one
+/// at a time to stay a polite client.
 ///
 /// Displays a single-line progress counter (completed/total cars) that stays
-/// on the bottom line while downloads run. The counter tracks completions,
+/// on the bottom line while downloads run.
-/// not cars seen, since downloads run concurrently under the semaphore.
 ///
 /// Returns the first error encountered, or `Ok(())` if all downloads succeeded.
 pub async fn fetch_times(cars_db_path: &str, times_dir: &str) -> Result<(), AppError> {
@@ -379,47 +383,19 @@ pub async fn fetch_times(cars_db_path: &str, times_dir: &str) -> Result<(), AppE
     );
     progress.set_message("Downloading track times for car");
 
-    let semaphore = Arc::new(Semaphore::new(CONCURRENCY_LIMIT));
-    let mut handles = vec![];
-
-    for car in car_list {
-        let permit = semaphore
-            .clone()
-            .acquire_owned()
-            .await
-            .map_err(|e| AppError::Network(format!("Semaphore closed: {e}")))?;
-        let times_dir = times_dir.to_string();
-        let progress = progress.clone();
-        handles.push(tokio::spawn(async move {
-            let _permit = permit; // held until end of block
-            let result = fetch_car(&car.rid, &times_dir).await;
-            progress.inc(1);
-            result
-        }));
-    }
-
-    let results = join_all(handles).await;
-    // Clear the counter before error logging so warnings don't garble the line.
-    progress.finish_and_clear();
     let mut first_error: Option<AppError> = None;
-    for result in results {
+    for car in car_list {
-        match result {
+        if let Err(e) = fetch_car(&car.rid, times_dir).await {
-            Ok(Ok(())) => {}
-            Ok(Err(e)) => {
             log::warn!("{e}");
             if first_error.is_none() {
                 first_error = Some(e);
             }
         }
-            Err(e) => {
+        progress.inc(1);
-                let msg = AppError::Network(format!("Task join error: {e}"));
-                log::warn!("{msg}");
-                if first_error.is_none() {
-                    first_error = Some(msg);
-                }
-            }
-        }
     }
+
+    // Clear the counter before error logging so warnings don't garble the line.
+    progress.finish_and_clear();
     first_error.map_or(Ok(()), Err)
 }