Use brotli for reducing the size of the text snapshots (#1482)

changedetectionio/model/Watch.py

@@ -241,9 +241,32 @@ class model(dict):
         bump = self.history
         return self.__newest_history_key
 
+    def get_history_snapshot(self, timestamp):
+        import brotli
+        filepath = self.history[timestamp]
+
+        # See if a brotli versions exists and switch to that
+        if not filepath.endswith('.br') and os.path.isfile(f"{filepath}.br"):
+            filepath = f"{filepath}.br"
+
+        # OR in the backup case that the .br does not exist, but the plain one does
+        if filepath.endswith('.br') and not os.path.isfile(filepath):
+            if os.path.isfile(filepath.replace('.br', '')):
+                filepath = filepath.replace('.br', '')
+
+        if filepath.endswith('.br'):
+            # Brotli doesnt have a fileheader to detect it, so we rely on filename
+            # https://www.rfc-editor.org/rfc/rfc7932
+            with open(filepath, 'rb') as f:
+                return(brotli.decompress(f.read()).decode('utf-8'))
+
+        with open(filepath, 'r', encoding='utf-8', errors='ignore') as f:
+            return f.read()
+
     # Save some text file to the appropriate path and bump the history
     # result_obj from fetch_site_status.run()
     def save_history_text(self, contents, timestamp, snapshot_id):
+        import brotli
 
         self.ensure_data_dir_exists()
 
@@ -252,16 +275,21 @@ class model(dict):
         if self.__newest_history_key and int(timestamp) == int(self.__newest_history_key):
             time.sleep(timestamp - self.__newest_history_key)
 
-        snapshot_fname = f"{snapshot_id}.txt"
+        threshold = int(os.getenv('SNAPSHOT_BROTLI_COMPRESSION_THRESHOLD', 1024))
+        skip_brotli = strtobool(os.getenv('DISABLE_BROTLI_TEXT_SNAPSHOT', 'False'))
 
-        # Only write if it does not exist, this is so that we dont bother re-saving the same data by checksum under different filenames.
-        dest = os.path.join(self.watch_data_dir, snapshot_fname)
-        if not os.path.exists(dest):
-            # in /diff/ and /preview/ we are going to assume for now that it's UTF-8 when reading
-            # most sites are utf-8 and some are even broken utf-8
-            with open(dest, 'wb') as f:
-                f.write(contents)
-                f.close()
+        if not skip_brotli and len(contents) > threshold:
+            snapshot_fname = f"{snapshot_id}.txt.br"
+            dest = os.path.join(self.watch_data_dir, snapshot_fname)
+            if not os.path.exists(dest):
+                with open(dest, 'wb') as f:
+                    f.write(brotli.compress(contents, mode=brotli.MODE_TEXT))
+        else:
+            snapshot_fname = f"{snapshot_id}.txt"
+            dest = os.path.join(self.watch_data_dir, snapshot_fname)
+            if not os.path.exists(dest):
+                with open(dest, 'wb') as f:
+                    f.write(contents)
 
         # Append to index
         # @todo check last char was \n
@@ -359,6 +387,7 @@ class model(dict):
             return fname
         return False
 
+
     def pause(self):
         self['paused'] = True
 
@@ -388,8 +417,8 @@ class model(dict):
         # self.history will be keyed with the full path
         for k, fname in self.history.items():
             if os.path.isfile(fname):
-                with open(fname, "r") as f:
-                    contents = f.read()
+                if True:
+                    contents = self.get_history_snapshot(k)
                     res = re.findall(regex, contents, re.MULTILINE)
                     if res:
                         if not csv_writer: