Refactor and change default retry-after delay to 60 seconds

Author: rayluo

msal/throttled_http_client.py

@@ -13,27 +13,31 @@ def _hash(raw):
     return sha256(repr(raw).encode("utf-8")).hexdigest()
 
 
-def _handle_http_429_5xx_retry_after(result=None, **ignored):
+def _parse_http_429_5xx_retry_after(result=None, **ignored):
+    """Return seconds to throttle"""
     assert result is not None, """
         The signature defines it with a default value None,
         only because the its shape is already decided by the
         IndividualCache's.__call__().
         In actual code path, the result parameter here won't be None.
         """
     response = result
-    lowercase_headers = {  # MSAL's HttpClient may not have headers
-        k.lower(): v for k, v in getattr(response, "headers", {}).items()}
-    default = 600
+    lowercase_headers = {k.lower(): v for k, v in getattr(
+        # Historically, MSAL's HttpResponse does not always have headers
+        response, "headers", {}).items()}
+    if not (response.status_code == 429 or response.status_code >= 500
+            or "retry-after" in lowercase_headers):
+        return 0  # Quick exit
+    default = 60  # Recommended at the end of
+        # https://identitydivision.visualstudio.com/devex/_git/AuthLibrariesApiReview?version=GBdev&path=%2FService%20protection%2FIntial%20set%20of%20protection%20measures.md&_a=preview
+    retry_after = int(lowercase_headers.get("retry-after", default))
     try:
         # AAD's retry_after uses integer format only
         # https://stackoverflow.microsoft.com/questions/264931/264932
-        retry_after = int(lowercase_headers.get("retry-after", default))
+        delay_seconds = int(retry_after)
     except ValueError:
-        retry_after = default
-    return min(3600, retry_after) if (
-        response.status_code == 429 or response.status_code >= 500
-        or "retry-after" in lowercase_headers
-        ) else 0
+        delay_seconds = default
+    return min(3600, delay_seconds)
 
 
 def _extract_data(kwargs, key, default=None):
@@ -73,7 +77,7 @@ def __init__(self, http_client, http_cache):
                             _extract_data(kwargs, "code",  # "account" of auth code grant
                                 _extract_data(kwargs, "username")))),  # "account" of ROPC
                     ),
-            expires_in=_handle_http_429_5xx_retry_after,
+            expires_in=_parse_http_429_5xx_retry_after,
             )(_post)
 
         _post = IndividualCache(  # It covers the "UI required cache"