Advises the kernel to not cache log files generated by Airflow

airflow/utils/cli.py

@@ -34,6 +34,7 @@
 from airflow import settings
 from airflow.exceptions import AirflowException
 from airflow.utils import cli_action_loggers
+from airflow.utils.log.non_caching_file_handler import NonCachingFileHandler
 from airflow.utils.platform import getuser, is_terminal_support_colors
 from airflow.utils.session import provide_session
 
@@ -244,7 +245,7 @@ def setup_locations(process, pid=None, stdout=None, stderr=None, log=None):
 def setup_logging(filename):
     """Creates log file handler for daemon process"""
     root = logging.getLogger()
-    handler = logging.FileHandler(filename)
+    handler = NonCachingFileHandler(filename)
     formatter = logging.Formatter(settings.SIMPLE_LOG_FORMAT)
     handler.setFormatter(formatter)
     root.addHandler(handler)

airflow/utils/log/file_processor_handler.py

@@ -23,6 +23,7 @@
 
 from airflow import settings
 from airflow.utils.helpers import parse_template_string
+from airflow.utils.log.non_caching_file_handler import NonCachingFileHandler
 
 
 class FileProcessorHandler(logging.Handler):
@@ -54,7 +55,7 @@ def set_context(self, filename):
         :param filename: filename in which the dag is located
         """
         local_loc = self._init_file(filename)
-        self.handler = logging.FileHandler(local_loc)
+        self.handler = NonCachingFileHandler(local_loc)
         self.handler.setFormatter(self.formatter)
         self.handler.setLevel(self.level)
 

airflow/utils/log/file_task_handler.py

@@ -26,6 +26,7 @@
 
 from airflow.configuration import AirflowConfigException, conf
 from airflow.utils.helpers import parse_template_string
+from airflow.utils.log.non_caching_file_handler import NonCachingFileHandler
 
 if TYPE_CHECKING:
     from airflow.models import TaskInstance
@@ -55,7 +56,7 @@ def set_context(self, ti: "TaskInstance"):
         :param ti: task instance object
         """
         local_loc = self._init_file(ti)
-        self.handler = logging.FileHandler(local_loc, encoding='utf-8')
+        self.handler = NonCachingFileHandler(local_loc, encoding='utf-8')
         if self.formatter:
             self.handler.setFormatter(self.formatter)
         self.handler.setLevel(self.level)

airflow/utils/log/non_caching_file_handler.py

@@ -0,0 +1,46 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+import logging
+import os
+
+
+class NonCachingFileHandler(logging.FileHandler):
+    """
+    This is an extension of the python FileHandler that advises the Kernel to not cache the file
+    in PageCache when it is written. While there is nothing wrong with such cache (it will be cleaned
+    when memory is needed), it causes ever-growing memory usage when scheduler is running as it keeps
+    on writing new log files and the files are not rotated later on. This might lead to confusion
+    for our users, who are monitoring memory usage of Scheduler - without realising that it is
+    harmless and expected in this case.
+
+    See https://github.com/apache/airflow/issues/14924
+
+    Adding the advice to Kernel might help with not generating the cache memory growth in the first place.
+    """
+
+    def _open(self):
+        wrapper = logging.FileHandler._open(self)
+        try:
+            fd = wrapper.fileno()
+            os.posix_fadvise(fd, 0, 0, os.POSIX_FADV_DONTNEED)
+        except Exception:
+            # in case either file descriptor cannot be retrieved or fadvise is not available
+            # we should simply return the wrapper retrieved by FileHandler's open method
+            # the advise to the kernel is just an advise and if we cannot give it, we won't
+            pass
+        return wrapper