[s3] Cache Cloudfront Signers (#1417)

CHANGELOG.rst

@@ -10,6 +10,7 @@ S3
 - Pull ``AWS_SESSION_TOKEN`` from the environment (`#1399`_)
 - Fix newline handling for text mode files (`#1381`_)
 - Do not sign URLs when ``querystring_auth=False`` e.g public buckets or static files (`#1402`_)
+- Cache CloudFront Signers (`#1417`_)
 
 Azure
 -----
@@ -22,6 +23,7 @@ Azure
 .. _#1402: https://github.com/jschneier/django-storages/pull/1402
 .. _#1403: https://github.com/jschneier/django-storages/pull/1403
 .. _#1414: https://github.com/jschneier/django-storages/pull/1414
+.. _#1417: https://github.com/jschneier/django-storages/pull/1417
 
 
 1.14.3 (2024-05-04)

storages/backends/s3.py

@@ -311,6 +311,8 @@ class S3Storage(CompressStorageMixin, BaseStorage):
     # settings/args are ignored.
     config = None
 
+    _signers = {}  # noqa: RUF012
+
     def __init__(self, **settings):
         omitted = object()
         if not hasattr(self, "cloudfront_signer"):
@@ -372,7 +374,12 @@ def __init__(self, **settings):
                 self.cloudfront_signer = None
 
     def get_cloudfront_signer(self, key_id, key):
-        return _cloud_front_signer_from_pem(key_id, key)
+        cache_key = f"{key_id}:{key}"
+        if cache_key not in self.__class__._signers:
+            self.__class__._signers[cache_key] = _cloud_front_signer_from_pem(
+                key_id, key
+            )
+        return self.__class__._signers[cache_key]
 
     def get_default_settings(self):
         return {