An attempt to solve Issue 218 for caching requests

iiif_prezi3/helpers/set_hwd_from_iiif.py

@@ -1,13 +1,33 @@
+from functools import lru_cache
 import requests
 
 from ..loader import monkeypatch_schema
 from ..skeleton import Canvas, Resource, ResourceItem
 
 
+@lru_cache(maxsize=3)
+def get_info_json(url):
+    """Cache the info.json response of the URL request.
+
+    Args:
+        url (str): An HTTP URL for the IIIF image endpoint.
+
+    Returns:
+        dict: The info.json as a dictionary.
+    """
+    response = requests.get(url)
+    # if response is not 200, raise exception
+    if response.status_code != requests.codes.ok:
+        response.raise_for_status()
+    # if response is not valid json, request will raise
+    # requests.exceptions.JSONDecodeError
+    # — handle or document and let calling code handle?
+    return response.json()
+
+
 class SetHwdFromIIIF:
     # should probably be added to canvas helpers
-
-    def set_hwd_from_iiif(self, url):
+    def set_hwd_from_iiif(self, url, use_cache=True):
         """Set height and width on a Canvas object.
 
         Requests IIIF Image information remotely for an
@@ -16,22 +36,18 @@ def set_hwd_from_iiif(self, url):
 
         Args:
             url (str): An HTTP URL for the IIIF image endpoint.
+            use_cache (bool): If True multiple requests to the same URL will
+            use the cached response without making new requests to the server
+            (default True).
         """
         # resource url may or may not end with info.json;
         # add if not present
         if not url.endswith("info.json"):
             url = f"{ url.rstrip('/') }/info.json"
-
-        response = requests.get(url)
-        # if response is not 200, raise exception
-        if response.status_code != requests.codes.ok:
-            response.raise_for_status()
-        # if response is not valid json, request will raise
-        # requests.exceptions.JSONDecodeError
-        # — handle or document and let calling code handle?
-        resource_info = response.json()
+        resource_info = (
+            get_info_json(url) if use_cache else get_info_json.__wrapped__(url)
+        )
         self.set_hwd(resource_info.get("height"), resource_info.get("width"))
-
         return resource_info
 
 

tests/test_set_hwd_from_iiif.py

@@ -16,17 +16,17 @@ def test_set_hwd_from_iiif(self, mockrequest_get):
         image_id = 'http://iiif.example.org/images/1234abcd'
         image_info_url = f'{image_id}/info.json'
         # image api url without info.json
-        self.canvas.set_hwd_from_iiif(image_id)
+        self.canvas.set_hwd_from_iiif(image_id, use_cache=False)
         mockrequest_get.assert_called_with(image_info_url)
 
         # image api url with info.json
         mockrequest_get.reset_mock()
-        self.canvas.set_hwd_from_iiif(image_id)
+        self.canvas.set_hwd_from_iiif(image_id, use_cache=False)
         mockrequest_get.assert_called_with(image_info_url)
 
         # image url with trailing slash
         mockrequest_get.reset_mock()
-        self.canvas.set_hwd_from_iiif(image_id + "/")
+        self.canvas.set_hwd_from_iiif(image_id + "/", use_cache=False)
         mockrequest_get.assert_called_with(image_info_url)
 
         # non-200 response
@@ -37,15 +37,15 @@ def test_set_hwd_from_iiif(self, mockrequest_get):
         mockresponse.raise_for_status.side_effect = requests.exceptions.HTTPError
         mockrequest_get.return_value = mockresponse
         with self.assertRaises(requests.exceptions.HTTPError):
-            self.canvas.set_hwd_from_iiif(image_id)
+            self.canvas.set_hwd_from_iiif(image_id, use_cache=False)
             # non-200 should raise exception for status
             mockresponse.raise_for_status.assert_called_once()
 
         # 200 response but not valid json should raise exception
         mockresponse.status_code = 200
         mockresponse.json.side_effect = requests.exceptions.JSONDecodeError("", "", 0)  # JSONDecodeError needs arguments
         with self.assertRaises(requests.exceptions.JSONDecodeError):
-            self.canvas.set_hwd_from_iiif(image_id)
+            self.canvas.set_hwd_from_iiif(image_id, use_cache=False)
 
         # successful response with dimensions
         mockresponse.json.side_effect = None
@@ -59,5 +59,11 @@ def test_set_hwd_from_iiif(self, mockrequest_get):
         }
         # patch the method this helper calls so we can inspect
         with patch.object(Canvas, 'set_hwd') as mock_set_hwd:
-            self.canvas.set_hwd_from_iiif(image_id)
+            self.canvas.set_hwd_from_iiif(image_id, use_cache=False)
             mock_set_hwd.assert_called_with(6608, 4821)
+
+        # we test the caching mechanism
+        self.canvas.set_hwd_from_iiif(image_id, use_cache=True)  # will call get
+        mockrequest_get.reset_mock()
+        self.canvas.set_hwd_from_iiif(image_id, use_cache=True)  # should not
+        mockrequest_get.assert_not_called()