adding a tenacity based retry handler, etc

src/cluas_mcp/common/api_clients.py

@@ -1,3 +1,4 @@
+from tenacity import retry, stop_after_attempt, wait_exponential, retry_if_exception_type
 import requests
 import feedparser
 import xml.etree.ElementTree as ET

src/cluas_mcp/common/http.py

@@ -0,0 +1,38 @@
+from tenacity import (
+    retry,
+    stop_after_attempt,
+    wait_exponential,
+    retry_if_exception_type,
+)
+import requests
+
+
+def _raise_for_status(response: requests.Response) -> requests.Response:
+    """
+    Raise a retryable exception for transient HTTP issues.
+    We consider 429 and 5xx status codes retryable.
+    """
+    if response.status_code == 429 or response.status_code >= 500:
+        raise requests.exceptions.RequestException(
+            f"Transient HTTP error {response.status_code}"
+        )
+    return response
+
+
+@retry(
+    retry=retry_if_exception_type(requests.exceptions.RequestException),
+    stop=stop_after_attempt(3),
+    wait=wait_exponential(multiplier=1, min=4, max=10),
+)
+def fetch_with_retry(url: str) -> requests.Response:
+    """
+    Fetches a URL with retry logic suitable for academic APIs.
+
+    Retries on:
+      - Connection errors
+      - Timeouts
+      - 5xx responses
+      - 429 responses
+    """
+    response = requests.get(url, timeout=10)
+    return _raise_for_status(response)