made storagecounter use a watchdog (inotify) instead of excessive file reads

src/onionrblocks/storagecounter.py

@@ -1,8 +1,17 @@
 """
-    Onionr - Private P2P Communication
+Onionr - Private P2P Communication.
 
-    Keeps track of how much disk space we're using
+Keep track of how much disk space we're using
 """
+from pathlib import Path
+
+from threading import Thread
+
+from watchdog.observers import Observer
+from watchdog.events import FileSystemEventHandler
+
+import config
+from filepaths import usage_file
 """
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -17,17 +26,46 @@
     You should have received a copy of the GNU General Public License
     along with this program.  If not, see <https://www.gnu.org/licenses/>.
 """
-import config, filepaths
 config.reload()
+
+
+def _read_data_file(f) -> int:
+    amount = 0
+    try:
+        with open(f, 'r') as f:
+            amount = int(f.read())
+    except FileNotFoundError:
+        pass
+    except ValueError:
+        pass  # Possibly happens when the file is empty
+    return amount
+
+
 class StorageCounter:
     def __init__(self):
-        self.data_file = filepaths.usage_file
-        return
+        self.data_file = usage_file
+        self.amount: int = None
+        Path(self.data_file).touch()
 
-    def is_full(self)->bool:
-        """Returns if the allocated disk space is full (this is Onionr config, not true FS capacity)"""
+        def auto_refresher():
+            class Refresher(FileSystemEventHandler):
+                @staticmethod
+                def on_modified(event):
+                    self.amount = _read_data_file(self.data_file)
+            observer = Observer()
+            observer.schedule(Refresher(), usage_file)
+            observer.start()
+            while observer.is_alive():
+                # call import func with timeout
+                observer.join(120)
+        Thread(target=auto_refresher, daemon=True).start()
+        self.amount = _read_data_file(self.data_file)
+
+    def is_full(self) -> bool:
+        """Returns if the allocated disk space is full (this is Onionr config,
+        not true FS capacity)"""
         ret_data = False
-        if config.get('allocations.disk', 1073741824) <= (self.get_amount() + 1000):
+        if config.get('allocations.disk', 1073741824) <= (self.amount + 1000):
             ret_data = True
         return ret_data
 
@@ -35,26 +73,15 @@ class StorageCounter:
         with open(self.data_file, 'w') as data_file:
             data_file.write(str(data))
 
-    def get_amount(self)->int:
-        """Return how much disk space we're using (according to record)"""
-        ret_data = 0
-        try:
-            with open(self.data_file, 'r') as data_file:
-                ret_data = int(data_file.read())
-        except FileNotFoundError:
-            pass
-        except ValueError:
-            pass # Possibly happens when the file is empty
-        return ret_data
-
-    def get_percent(self)->int:
+    def get_percent(self) -> int:
         """Return percent (decimal/float) of disk space we're using"""
-        amount = self.get_amount()
+        amount = self.amount
         return round(amount / config.get('allocations.disk', 2000000000), 2)
 
-    def add_bytes(self, amount)->int:
-        """Record that we are now using more disk space, unless doing so would exceed configured max"""
-        new_amount = amount + self.get_amount()
+    def add_bytes(self, amount) -> int:
+        """Record that we are now using more disk space,
+        unless doing so would exceed configured max"""
+        new_amount = amount + self.amount
         ret_data = new_amount
         if new_amount > config.get('allocations.disk', 2000000000):
             ret_data = False
@@ -62,8 +89,8 @@ class StorageCounter:
             self._update(new_amount)
         return ret_data
 
-    def remove_bytes(self, amount)->int:
+    def remove_bytes(self, amount) -> int:
         """Record that we are now using less disk space"""
-        new_amount = self.get_amount() - amount
+        new_amount = self.amount - amount
         self._update(new_amount)
         return new_amount