refactor: implement retry mechanism for API calls in Anthropic, OpenAI Chat, and OpenAI Responses providers

- Replaced direct API call handling with a retry mechanism using `send_with_retry`.
- Improved error handling and response management for better reliability in network requests.

server/src/provider/anthropic.rs

@@ -11,8 +11,10 @@ use crate::{
 };
 
 use super::{
-    merge_extra_params, recorder::recorded_headers, CallRecorder, FinishReason, ModelEvent,
-    Provider, ProviderStream,
+    merge_extra_params,
+    recorder::recorded_headers,
+    retry::{send_with_retry, Attempt, RetryPolicy},
+    CallRecorder, FinishReason, ModelEvent, Provider, ProviderStream,
 };
 
 const DEFAULT_MAX_OUTPUT_TOKENS: u64 = 65_000;
@@ -83,25 +85,17 @@ impl Provider for AnthropicProvider {
             if let Some(recorder) = &recorder {
                 recorder.request(recorded_headers(&config, &[("content-type", "application/json"), ("anthropic-version", "2023-06-01")]), &body).await?;
             }
-            let request = client.post(&config.request_url)
-                .header("x-api-key", &config.api_key).header("anthropic-version", "2023-06-01")
-                .headers(config.custom_headers.clone())
-                .json(&body).send();
-            let response = tokio::select! {
-                _ = cancellation.cancelled() => return,
-                response = request => response,
-            };
-            let response = response?;
-            if let Some(recorder) = &recorder {
-                recorder.response_headers(response.status().as_u16()).await?;
-            }
-            if !response.status().is_success() {
-                let status = response.status(); let bytes = response.bytes().await?;
-                if let Some(recorder) = &recorder { recorder.response_chunk(&bytes).await?; }
-                let text = String::from_utf8_lossy(&bytes);
-                Err(Error::Provider(format!("Anthropic {status}: {text}")))?;
-                return;
-            }
+            let attempt = send_with_retry(
+                "Anthropic",
+                || client.post(&config.request_url)
+                    .header("x-api-key", &config.api_key).header("anthropic-version", "2023-06-01")
+                    .headers(config.custom_headers.clone())
+                    .json(&body),
+                RetryPolicy::default(),
+                &cancellation,
+                recorder.as_ref(),
+            ).await?;
+            let Attempt::Response(response) = attempt else { return };
             yield ModelEvent::Start { model_call_id: call_id };
             let chunk_recorder = recorder.clone();
             let chunks = response.bytes_stream()

server/src/provider/mod.rs

@@ -4,6 +4,7 @@ mod normalize;
 mod openai_chat;
 mod openai_responses;
 mod recorder;
+mod retry;
 mod router;
 
 use std::pin::Pin;

server/src/provider/openai_chat.rs

@@ -16,8 +16,9 @@ use crate::{
 };
 
 use super::{
-    apply_openai_prompt_cache_key, merge_extra_params, recorder::recorded_headers, CallRecorder,
-    FinishReason, ModelEvent, Provider, ProviderStream,
+    apply_openai_prompt_cache_key, merge_extra_params, recorder::recorded_headers,
+    retry::{send_with_retry, Attempt, RetryPolicy},
+    CallRecorder, FinishReason, ModelEvent, Provider, ProviderStream,
 };
 
 #[derive(Default)]
@@ -86,33 +87,15 @@ impl Provider for OpenAiChatProvider {
             if let Some(recorder) = &recorder {
                 recorder.request(recorded_headers(&config, &[("content-type", "application/json")]), &body).await?;
             }
-            let request = client.post(&config.request_url)
-                .bearer_auth(&config.api_key).headers(config.custom_headers.clone()).json(&body).send();
-            let response = tokio::select! {
-                _ = cancellation.cancelled() => return,
-                response = request => response,
-            };
-            let response = match response {
-                Ok(r) => {
-                    tracing::debug!(status = r.status().as_u16(), "OpenAI Chat HTTP response received");
-                    r
-                }
-                Err(e) => {
-                    tracing::debug!(error = %e, "OpenAI Chat HTTP request failed");
-                    Err(Error::from(e))?
-                }
-            };
-            if let Some(recorder) = &recorder {
-                recorder.response_headers(response.status().as_u16()).await?;
-            }
-            if !response.status().is_success() {
-                let status = response.status();
-                let bytes = response.bytes().await?;
-                if let Some(recorder) = &recorder { recorder.response_chunk(&bytes).await?; }
-                let text = String::from_utf8_lossy(&bytes);
-                Err(Error::Provider(format!("OpenAI Chat {status}: {text}")))?;
-                return;
-            }
+            let attempt = send_with_retry(
+                "OpenAI Chat",
+                || client.post(&config.request_url)
+                    .bearer_auth(&config.api_key).headers(config.custom_headers.clone()).json(&body),
+                RetryPolicy::default(),
+                &cancellation,
+                recorder.as_ref(),
+            ).await?;
+            let Attempt::Response(response) = attempt else { return };
             yield ModelEvent::Start { model_call_id: call_id };
             let chunk_recorder = recorder.clone();
             let chunks = response.bytes_stream()

server/src/provider/openai_responses.rs

@@ -13,8 +13,9 @@ use crate::{
 };
 
 use super::{
-    apply_openai_prompt_cache_key, merge_extra_params, recorder::recorded_headers, CallRecorder,
-    FinishReason, ModelEvent, Provider, ProviderStream,
+    apply_openai_prompt_cache_key, merge_extra_params, recorder::recorded_headers,
+    retry::{send_with_retry, Attempt, RetryPolicy},
+    CallRecorder, FinishReason, ModelEvent, Provider, ProviderStream,
 };
 
 #[derive(Default)]
@@ -83,23 +84,15 @@ impl Provider for OpenAiResponsesProvider {
             if let Some(recorder) = &recorder {
                 recorder.request(recorded_headers(&config, &[("content-type", "application/json")]), &body).await?;
             }
-            let request = client.post(&config.request_url)
-                .bearer_auth(&config.api_key).headers(config.custom_headers.clone()).json(&body).send();
-            let response = tokio::select! {
-                _ = cancellation.cancelled() => return,
-                response = request => response,
-            };
-            let response = response?;
-            if let Some(recorder) = &recorder {
-                recorder.response_headers(response.status().as_u16()).await?;
-            }
-            if !response.status().is_success() {
-                let status = response.status(); let bytes = response.bytes().await?;
-                if let Some(recorder) = &recorder { recorder.response_chunk(&bytes).await?; }
-                let text = String::from_utf8_lossy(&bytes);
-                Err(Error::Provider(format!("OpenAI Responses {status}: {text}")))?;
-                return;
-            }
+            let attempt = send_with_retry(
+                "OpenAI Responses",
+                || client.post(&config.request_url)
+                    .bearer_auth(&config.api_key).headers(config.custom_headers.clone()).json(&body),
+                RetryPolicy::default(),
+                &cancellation,
+                recorder.as_ref(),
+            ).await?;
+            let Attempt::Response(response) = attempt else { return };
             yield ModelEvent::Start { model_call_id: call_id };
             let chunk_recorder = recorder.clone();
             let chunks = response.bytes_stream()

server/src/provider/retry.rs

@@ -0,0 +1,242 @@
+use std::time::Duration;
+
+use tokio_util::sync::CancellationToken;
+
+use crate::{Error, Result};
+
+use super::CallRecorder;
+
+#[derive(Clone, Copy, Debug)]
+pub(crate) struct RetryPolicy {
+    pub retries: u32,
+    pub delay: Duration,
+}
+
+impl Default for RetryPolicy {
+    fn default() -> Self {
+        Self {
+            retries: 5,
+            delay: Duration::from_secs(5),
+        }
+    }
+}
+
+#[derive(Debug)]
+pub(crate) enum Attempt {
+    Response(reqwest::Response),
+    Cancelled,
+}
+
+pub(crate) async fn send_with_retry<F>(
+    label: &str,
+    build: F,
+    policy: RetryPolicy,
+    cancellation: &CancellationToken,
+    recorder: Option<&CallRecorder>,
+) -> Result<Attempt>
+where
+    F: Fn() -> reqwest::RequestBuilder,
+{
+    for attempt in 0..=policy.retries {
+        let response = tokio::select! {
+            _ = cancellation.cancelled() => return Ok(Attempt::Cancelled),
+            response = build().send() => response,
+        }?;
+        if let Some(recorder) = recorder {
+            recorder.response_headers(response.status().as_u16()).await?;
+        }
+        if response.status().is_success() {
+            return Ok(Attempt::Response(response));
+        }
+        let status = response.status();
+        let bytes = response.bytes().await?;
+        if let Some(recorder) = recorder {
+            recorder.response_chunk(&bytes).await?;
+        }
+        if attempt == policy.retries {
+            let text = String::from_utf8_lossy(&bytes);
+            return Err(Error::Provider(format!("{label} {status}: {text}")));
+        }
+        tracing::warn!(
+            provider = label,
+            status = status.as_u16(),
+            attempt = attempt + 1,
+            retries = policy.retries,
+            delay_ms = policy.delay.as_millis(),
+            "provider returned a non-success status, retrying"
+        );
+        tokio::select! {
+            _ = cancellation.cancelled() => return Ok(Attempt::Cancelled),
+            _ = tokio::time::sleep(policy.delay) => {}
+        }
+    }
+    unreachable!("the retry loop returns on the final attempt")
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    use std::sync::{
+        atomic::{AtomicU32, Ordering},
+        Arc,
+    };
+
+    use axum::{extract::State, http::StatusCode, routing::post, Router};
+
+    fn fast(retries: u32) -> RetryPolicy {
+        RetryPolicy {
+            retries,
+            delay: Duration::from_millis(20),
+        }
+    }
+
+    async fn status_server(statuses: Vec<u16>) -> (String, Arc<AtomicU32>) {
+        async fn endpoint(
+            State((statuses, calls)): State<(Arc<Vec<u16>>, Arc<AtomicU32>)>,
+        ) -> (StatusCode, String) {
+            let index = calls.fetch_add(1, Ordering::SeqCst) as usize;
+            let status = statuses
+                .get(index)
+                .copied()
+                .unwrap_or_else(|| *statuses.last().unwrap());
+            (
+                StatusCode::from_u16(status).unwrap(),
+                format!("body for attempt {index}"),
+            )
+        }
+
+        let calls = Arc::new(AtomicU32::new(0));
+        let app = Router::new()
+            .route("/responses", post(endpoint))
+            .with_state((Arc::new(statuses), calls.clone()));
+        let listener = tokio::net::TcpListener::bind("127.0.0.1:0").await.unwrap();
+        let address = listener.local_addr().unwrap();
+        tokio::spawn(async move { axum::serve(listener, app).await.unwrap() });
+        (format!("http://{address}/responses"), calls)
+    }
+
+    fn sender(url: String) -> impl Fn() -> reqwest::RequestBuilder {
+        let client = reqwest::Client::new();
+        move || client.post(&url).json(&serde_json::json!({"stream": true}))
+    }
+
+    #[test]
+    fn the_default_policy_retries_five_times_every_five_seconds() {
+        let policy = RetryPolicy::default();
+        assert_eq!(policy.retries, 5);
+        assert_eq!(policy.delay, Duration::from_secs(5));
+    }
+
+    #[tokio::test]
+    async fn a_non_success_response_is_retried_until_it_succeeds() {
+        let (url, calls) = status_server(vec![429, 500, 200]).await;
+
+        let attempt = send_with_retry(
+            "Test",
+            sender(url),
+            fast(5),
+            &CancellationToken::new(),
+            None,
+        )
+        .await
+        .unwrap();
+
+        let Attempt::Response(response) = attempt else {
+            panic!("expected a response");
+        };
+        assert_eq!(response.status(), StatusCode::OK);
+        assert_eq!(calls.load(Ordering::SeqCst), 3);
+    }
+
+    #[tokio::test]
+    async fn the_last_non_success_response_fails_after_the_retry_budget() {
+        let (url, calls) = status_server(vec![429]).await;
+
+        let error = send_with_retry(
+            "Test",
+            sender(url),
+            fast(5),
+            &CancellationToken::new(),
+            None,
+        )
+        .await
+        .unwrap_err();
+
+        assert!(
+            matches!(&error, Error::Provider(message) if message.contains("Test 429")),
+            "unexpected error: {error}"
+        );
+        assert_eq!(calls.load(Ordering::SeqCst), 6);
+    }
+
+    #[tokio::test]
+    async fn every_retry_waits_for_the_configured_delay() {
+        let (url, _) = status_server(vec![429, 429, 200]).await;
+        let started = std::time::Instant::now();
+
+        send_with_retry(
+            "Test",
+            sender(url),
+            RetryPolicy {
+                retries: 5,
+                delay: Duration::from_millis(150),
+            },
+            &CancellationToken::new(),
+            None,
+        )
+        .await
+        .unwrap();
+
+        assert!(
+            started.elapsed() >= Duration::from_millis(300),
+            "retries did not wait: {:?}",
+            started.elapsed()
+        );
+    }
+
+    #[tokio::test]
+    async fn cancellation_during_the_retry_delay_stops_the_attempts() {
+        let (url, calls) = status_server(vec![429]).await;
+        let cancellation = CancellationToken::new();
+        let deadline = cancellation.clone();
+        tokio::spawn(async move {
+            tokio::time::sleep(Duration::from_millis(100)).await;
+            deadline.cancel();
+        });
+
+        let attempt = send_with_retry(
+            "Test",
+            sender(url),
+            RetryPolicy {
+                retries: 5,
+                delay: Duration::from_millis(500),
+            },
+            &cancellation,
+            None,
+        )
+        .await
+        .unwrap();
+
+        assert!(matches!(attempt, Attempt::Cancelled));
+        assert_eq!(calls.load(Ordering::SeqCst), 1);
+    }
+
+    #[tokio::test]
+    async fn a_success_response_is_returned_without_any_retry() {
+        let (url, calls) = status_server(vec![200]).await;
+
+        let attempt = send_with_retry(
+            "Test",
+            sender(url),
+            fast(5),
+            &CancellationToken::new(),
+            None,
+        )
+        .await
+        .unwrap();
+
+        assert!(matches!(attempt, Attempt::Response(_)));
+        assert_eq!(calls.load(Ordering::SeqCst), 1);
+    }
+}