Add PeriodicallyFlushingMemoryHandler

synapse/logging/handlers.py

@@ -0,0 +1,43 @@
+import logging
+import time
+from logging import Handler
+from logging.handlers import MemoryHandler
+from threading import Thread
+from typing import Optional
+
+
+class PeriodicallyFlushingMemoryHandler(MemoryHandler):
+    """
+    This is a subclass of MemoryHandler which additionally spawns a background
+    thread which periodically flushes the buffers.
+
+    This prevents messages from being buffered for too long.
+    """
+
+    def __init__(
+        self,
+        capacity: int,
+        flushLevel: int = logging.ERROR,
+        target: Optional[Handler] = None,
+        flushOnClose: bool = True,
+        period: float = 5.0,
+    ) -> None:
+        super().__init__(capacity, flushLevel, target, flushOnClose)
+
+        self._flush_period: float = period
+        self._active: bool = True
+
+        self._flushing_thread: Thread = Thread(
+            name="PeriodicallyFlushingMemoryHandler flushing thread",
+            target=self._flush_periodically,
+        )
+        self._flushing_thread.start()
+
+    def _flush_periodically(self):
+        while self._active:
+            self.flush()
+            time.sleep(self._flush_period)
+
+    def close(self) -> None:
+        self._active = False
+        super().close()