VisualSelector - Use 'deflate' for storing elements.json, 90% file size reduction (#2794)

changedetectionio/flask_app.py

@@ -1297,12 +1297,23 @@ def changedetection_app(config=None, datastore_o=None):
 
             # These files should be in our subdirectory
             try:
-                # set nocache, set content-type
-                response = make_response(send_from_directory(os.path.join(datastore_o.datastore_path, filename), "elements.json"))
-                response.headers['Content-type'] = 'application/json'
+                # set nocache, set content-type,
+                # `filename` is actually directory UUID of the watch
+                watch_directory = str(os.path.join(datastore_o.datastore_path, filename))
+                response = None
+                if os.path.isfile(os.path.join(watch_directory, "elements.deflate")):
+                    response = make_response(send_from_directory(watch_directory, "elements.deflate"))
+                    response.headers['Content-Type'] = 'application/json'
+                    response.headers['Content-Encoding'] = 'deflate'
+                else:
+                    logger.error(f'Request elements.deflate at "{watch_directory}" but was notfound.')
+                    abort(404)
+
+                if response:
                     response.headers['Cache-Control'] = 'no-cache, no-store, must-revalidate'
                     response.headers['Pragma'] = 'no-cache'
-                response.headers['Expires'] = 0
+                    response.headers['Expires'] = "0"
+
                 return response
 
             except FileNotFoundError:

changedetectionio/model/Watch.py

@@ -538,16 +538,17 @@ class model(watch_base):
 
     def save_xpath_data(self, data, as_error=False):
         import json
+        import zlib
 
         if as_error:
-            target_path = os.path.join(self.watch_data_dir, "elements-error.json")
+            target_path = os.path.join(str(self.watch_data_dir), "elements-error.deflate")
         else:
-            target_path = os.path.join(self.watch_data_dir, "elements.json")
+            target_path = os.path.join(str(self.watch_data_dir), "elements.deflate")
 
         self.ensure_data_dir_exists()
 
-        with open(target_path, 'w') as f:
-            f.write(json.dumps(data))
+        with open(target_path, 'wb') as f:
+            f.write(zlib.compress(json.dumps(data).encode()))
             f.close()
 
     # Save as PNG, PNG is larger but better for doing visual diff in the future

changedetectionio/static/js/visual-selector.js

@@ -132,6 +132,7 @@ $(document).ready(() => {
         }).done((data) => {
             $fetchingUpdateNoticeElem.html("Rendering..");
             selectorData = data;
+
             sortScrapedElementsBySize();
             console.log(`Reported browser width from backend: ${data['browser_width']}`);
 

changedetectionio/store.py

@@ -374,7 +374,7 @@ class ChangeDetectionStore:
     def visualselector_data_is_ready(self, watch_uuid):
         output_path = "{}/{}".format(self.datastore_path, watch_uuid)
         screenshot_filename = "{}/last-screenshot.png".format(output_path)
-        elements_index_filename = "{}/elements.json".format(output_path)
+        elements_index_filename = "{}/elements.deflate".format(output_path)
         if path.isfile(screenshot_filename) and  path.isfile(elements_index_filename) :
             return True
 
@@ -909,3 +909,18 @@ class ChangeDetectionStore:
             if self.data['watching'][uuid].get('in_stock_only'):
                 del (self.data['watching'][uuid]['in_stock_only'])
 
+    # Compress old elements.json to elements.deflate, saving disk, this compression is pretty fast.
+    def update_19(self):
+        import zlib
+
+        for uuid, watch in self.data['watching'].items():
+            json_path = os.path.join(self.datastore_path, uuid, "elements.json")
+            deflate_path = os.path.join(self.datastore_path, uuid, "elements.deflate")
+
+            if os.path.exists(json_path):
+                with open(json_path, "rb") as f_j:
+                    with open(deflate_path, "wb") as f_d:
+                        logger.debug(f"Compressing {str(json_path)} to {str(deflate_path)}..")
+                        f_d.write(zlib.compress(f_j.read()))
+                        os.unlink(json_path)
+

changedetectionio/tests/visualselector/test_fetch_data.py

@@ -54,15 +54,21 @@ def test_visual_selector_content_ready(client, live_server, measure_memory_usage
 
 
     assert os.path.isfile(os.path.join('test-datastore', uuid, 'last-screenshot.png')), "last-screenshot.png should exist"
-    assert os.path.isfile(os.path.join('test-datastore', uuid, 'elements.json')), "xpath elements.json data should exist"
+    assert os.path.isfile(os.path.join('test-datastore', uuid, 'elements.deflate')), "xpath elements.deflate data should exist"
 
     # Open it and see if it roughly looks correct
-    with open(os.path.join('test-datastore', uuid, 'elements.json'), 'r') as f:
-        json.load(f)
+    with open(os.path.join('test-datastore', uuid, 'elements.deflate'), 'rb') as f:
+        import zlib
+        compressed_data = f.read()
+        decompressed_data = zlib.decompress(compressed_data)
+        # See if any error was thrown
+        json_data = json.loads(decompressed_data.decode('utf-8'))
 
     # Attempt to fetch it via the web hook that the browser would use
     res = client.get(url_for('static_content', group='visual_selector_data', filename=uuid))
-    json.loads(res.data)
+    decompressed_data = zlib.decompress(res.data)
+    json_data = json.loads(decompressed_data.decode('utf-8'))
+    
     assert res.mimetype == 'application/json'
     assert res.status_code == 200