From 78c18a9b9a1445f7c755929917a790ba02b4a5e0 Mon Sep 17 00:00:00 2001
From: Avram Lubkin <git_hub@avram.us>
Date: Sun, 30 Jul 2017 05:36:33 -0400
Subject: bpo-30962: Added caching to Logger.isEnabledFor() (GH-2752)

---
 Lib/logging/__init__.py  | 30 +++++++++++++++++++++---
 Lib/test/test_logging.py | 60 +++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 86 insertions(+), 4 deletions(-)

diff --git a/Lib/logging/__init__.py b/Lib/logging/__init__.py
index 64e24ee..f9bfb79 100644
--- a/Lib/logging/__init__.py
+++ b/Lib/logging/__init__.py
@@ -1244,6 +1244,19 @@ class Manager(object):
                 alogger.parent = c.parent
                 c.parent = alogger
 
+    def _clear_cache(self):
+        """
+        Clear the cache for all loggers in loggerDict
+        Called when level changes are made
+        """
+
+        _acquireLock()
+        for logger in self.loggerDict.values():
+            if isinstance(logger, Logger):
+                logger._cache.clear()
+        self.root._cache.clear()
+        _releaseLock()
+
 #---------------------------------------------------------------------------
 #   Logger classes and functions
 #---------------------------------------------------------------------------
@@ -1274,12 +1287,14 @@ class Logger(Filterer):
         self.propagate = True
         self.handlers = []
         self.disabled = False
+        self._cache = {}
 
     def setLevel(self, level):
         """
         Set the logging level of this logger.  level must be an int or a str.
         """
         self.level = _checkLevel(level)
+        self.manager._clear_cache()
 
     def debug(self, msg, *args, **kwargs):
         """
@@ -1543,9 +1558,17 @@ class Logger(Filterer):
         """
         Is this logger enabled for level 'level'?
         """
-        if self.manager.disable >= level:
-            return False
-        return level >= self.getEffectiveLevel()
+        try:
+            return self._cache[level]
+        except KeyError:
+            _acquireLock()
+            if self.manager.disable >= level:
+                is_enabled = self._cache[level] = False
+            else:
+                is_enabled = self._cache[level] = level >= self.getEffectiveLevel()
+            _releaseLock()
+
+            return is_enabled
 
     def getChild(self, suffix):
         """
@@ -1910,6 +1933,7 @@ def disable(level=CRITICAL):
     Disable all logging calls of severity 'level' and below.
     """
     root.manager.disable = level
+    root.manager._clear_cache()
 
 def shutdown(handlerList=_handlerList):
     """
diff --git a/Lib/test/test_logging.py b/Lib/test/test_logging.py
index 880f4e8..8884562 100644
--- a/Lib/test/test_logging.py
+++ b/Lib/test/test_logging.py
@@ -135,7 +135,9 @@ class BaseTest(unittest.TestCase):
             logging._handlers.clear()
             logging._handlers.update(self.saved_handlers)
             logging._handlerList[:] = self.saved_handler_list
-            loggerDict = logging.getLogger().manager.loggerDict
+            manager = logging.getLogger().manager
+            manager.disable = 0
+            loggerDict = manager.loggerDict
             loggerDict.clear()
             loggerDict.update(self.saved_loggers)
             logger_states = self.logger_states
@@ -4094,6 +4096,62 @@ class LoggerTest(BaseTest):
                 unpickled = pickle.loads(s)
                 self.assertIs(unpickled, logger)
 
+    def test_caching(self):
+        root = self.root_logger
+        logger1 = logging.getLogger("abc")
+        logger2 = logging.getLogger("abc.def")
+
+        # Set root logger level and ensure cache is empty
+        root.setLevel(logging.ERROR)
+        self.assertEqual(logger2.getEffectiveLevel(), logging.ERROR)
+        self.assertEqual(logger2._cache, {})
+
+        # Ensure cache is populated and calls are consistent
+        self.assertTrue(logger2.isEnabledFor(logging.ERROR))
+        self.assertFalse(logger2.isEnabledFor(logging.DEBUG))
+        self.assertEqual(logger2._cache, {logging.ERROR: True, logging.DEBUG: False})
+        self.assertEqual(root._cache, {})
+        self.assertTrue(logger2.isEnabledFor(logging.ERROR))
+
+        # Ensure root cache gets populated
+        self.assertEqual(root._cache, {})
+        self.assertTrue(root.isEnabledFor(logging.ERROR))
+        self.assertEqual(root._cache, {logging.ERROR: True})
+
+        # Set parent logger level and ensure caches are emptied
+        logger1.setLevel(logging.CRITICAL)
+        self.assertEqual(logger2.getEffectiveLevel(), logging.CRITICAL)
+        self.assertEqual(logger2._cache, {})
+
+        # Ensure logger2 uses parent logger's effective level
+        self.assertFalse(logger2.isEnabledFor(logging.ERROR))
+
+        # Set level to NOTSET and ensure caches are empty
+        logger2.setLevel(logging.NOTSET)
+        self.assertEqual(logger2.getEffectiveLevel(), logging.CRITICAL)
+        self.assertEqual(logger2._cache, {})
+        self.assertEqual(logger1._cache, {})
+        self.assertEqual(root._cache, {})
+
+        # Verify logger2 follows parent and not root
+        self.assertFalse(logger2.isEnabledFor(logging.ERROR))
+        self.assertTrue(logger2.isEnabledFor(logging.CRITICAL))
+        self.assertFalse(logger1.isEnabledFor(logging.ERROR))
+        self.assertTrue(logger1.isEnabledFor(logging.CRITICAL))
+        self.assertTrue(root.isEnabledFor(logging.ERROR))
+
+        # Disable logging in manager and ensure caches are clear
+        logging.disable()
+        self.assertEqual(logger2.getEffectiveLevel(), logging.CRITICAL)
+        self.assertEqual(logger2._cache, {})
+        self.assertEqual(logger1._cache, {})
+        self.assertEqual(root._cache, {})
+
+        # Ensure no loggers are enabled
+        self.assertFalse(logger1.isEnabledFor(logging.CRITICAL))
+        self.assertFalse(logger2.isEnabledFor(logging.CRITICAL))
+        self.assertFalse(root.isEnabledFor(logging.CRITICAL))
+
 
 class BaseFileTest(BaseTest):
     "Base class for handler tests that write log files"
-- 
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