From bddab0208d6294527b1eb90dd2cbd31984c418f1 Mon Sep 17 00:00:00 2001
From: Matthew Stratford <hi@mstratford.net>
Date: Wed, 4 Nov 2020 01:19:56 +0000
Subject: [PATCH] Implement rate limiting to stop spamming state file writes

---
 helpers/state_manager.py | 68 +++++++++++++++++++++++++++++++++++-----
 player.py                | 17 +++++++---
 2 files changed, 74 insertions(+), 11 deletions(-)

diff --git a/helpers/state_manager.py b/helpers/state_manager.py
index 47685b6..dbe9052 100644
--- a/helpers/state_manager.py
+++ b/helpers/state_manager.py
@@ -2,6 +2,9 @@ from helpers.logging_manager import LoggingManager
 import json
 import os
 import logging
+import time
+from datetime import datetime
+from copy import copy
 from helpers.os_environment import resolve_external_file_path
 
 
@@ -9,8 +12,13 @@ class StateManager:
     filepath = None
     logger = None
     __state = {}
+    __state_in_file = {}
+    # Dict of times that params can be updated after, if the time is before current time, it can be written immediately.
+    __rate_limit_params_until = {}
+    __rate_limit_period_s = 0
 
-    def __init__(self, name, logger: LoggingManager, default_state=None):
+
+    def __init__(self, name, logger: LoggingManager, default_state=None, rate_limit_params=[], rate_limit_period_s = 5):
         self.logger = logger
 
         self.filepath = resolve_external_file_path("/state/" + name + ".json")
@@ -30,7 +38,8 @@ class StateManager:
 
         if file_state == "":
             self._log("State file is empty. Setting default state.")
-            self.state = default_state
+            self.state = copy(default_state)
+            self.__state_in_file = copy(self.state)
         else:
             try:
                 self.__state = json.loads(file_state)
@@ -38,14 +47,35 @@ class StateManager:
                 self._logException("Failed to parse state JSON. Resetting to default state.")
                 self.state = default_state
 
+        # Now setup the rate limiting
+        # Essentially rate limit all values to "now" to start with, allowing the first update
+        # of all vars to succeed.
+        for param in rate_limit_params:
+            self.__rate_limit_params_until[param] = self._currentTimeS
+        self.__rate_limit_period_s = rate_limit_period_s
+
     @property
     def state(self):
-        return self.__state
+        return copy(self.__state)
 
     @state.setter
     def state(self, state):
-        self.__state = state
+        self.__state = copy(state)
 
+    def write_to_file(self,state):
+        if self.__state_in_file == state:
+            # No change to be updated.
+            return
+
+        self.__state_in_file = state
+
+        # Make sure we're not manipulating state
+        state = copy(state)
+
+        now = datetime.now()
+
+        current_time = now.strftime("%H:%M:%S")
+        state["last_updated"] = current_time
         try:
             state_json = json.dumps(state, indent=2, sort_keys=True)
         except:
@@ -56,12 +86,36 @@ class StateManager:
                 file.write(state_json)
 
     def update(self, key, value):
-        state = self.state
-        state[key] = value
-        self.state = state
+        update_file = True
+        if (key in self.__rate_limit_params_until.keys()):
+            # The key we're trying to update is expected to be updating very often,
+            # We're therefore going to check before saving it.
+            if self.__rate_limit_params_until[key] > self._currentTimeS:
+                update_file = False
+            else:
+                self.__rate_limit_params_until[key] = self._currentTimeS + self.__rate_limit_period_s
+
+
+        state_to_update = self.state
+
+        if state_to_update[key] == value:
+            # We're trying to update the state with the same value.
+            # In this case, ignore the update
+            return
+
+        state_to_update[key] = value
+
+        self.state = state_to_update
+
+        if (update_file == True):
+            self.write_to_file(state_to_update)
 
     def _log(self, text, level=logging.INFO):
         self.logger.log.log(level, "State Manager: " + text)
 
     def _logException(self, text):
         self.logger.log.exception("State Manager: " + text)
+
+    @property
+    def _currentTimeS(self):
+        return time.time()
diff --git a/player.py b/player.py
index 69d4d41..631f6a8 100644
--- a/player.py
+++ b/player.py
@@ -43,6 +43,13 @@ class Player():
         "output": None
     }
 
+    __rate_limited_params = [
+        "pos",
+        "pos_offset",
+        "pos_true",
+        "remaining"
+    ]
+
     @property
     def isInit(self):
         try:
@@ -222,16 +229,18 @@ class Player():
         return True
 
     def _updateState(self, pos=None):
+
         self.state.update("initialised", self.isInit)
         if self.isInit:
-            if self.isPlaying:
+            if (pos):
+                self.state.update("pos", max(0, pos))
+            elif self.isPlaying:
                 # Get one last update in, incase we're about to pause/stop it.
                 self.state.update("pos", max(0, mixer.music.get_pos()/1000))
             self.state.update("playing", self.isPlaying)
             self.state.update("loaded", self.isLoaded)
 
-            if (pos):
-                self.state.update("pos", max(0, pos))
+
 
             self.state.update("pos_true", self.state.state["pos"] + self.state.state["pos_offset"])
 
@@ -262,7 +271,7 @@ class Player():
 
         self.logger = LoggingManager("channel" + str(channel))
 
-        self.state = StateManager("channel" + str(channel), self.logger, self.__default_state)
+        self.state = StateManager("channel" + str(channel), self.logger, self.__default_state, self.__rate_limited_params)
         self.state.update("channel", channel)
 
         loaded_state = copy.copy(self.state.state)