commit 7d8bcbd5bf8a6a31c78f9d8e4e51b19595209754
Author: Peter J. Holzer <hjp@hjp.at>
Date:   Sat Dec 3 12:19:00 2022 +0100

    Implement TimeoutSwitchingFileHandler

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..a988607
--- /dev/null
+++ b/README.md
@@ -0,0 +1,13 @@
+TimeoutSwitchingFileHandler
+===========================
+
+This is a logging file handler for the Python logging system.
+It automatically closes the log file after a period of inactivity
+(or after the file has been open for some time whichever comes first)
+and then opens a new file at the next emit.
+
+This is useful for long-running processes where short periods of
+activity alternate with periods of inactivity. Log switchs will
+typically occur during inactivity, so each log file will include one
+complete active period. Also, since the log files are closed, they can
+be safely compressed or removed.
diff --git a/timeoutswitchingfilehandler.py b/timeoutswitchingfilehandler.py
new file mode 100644
index 0000000..03cee4c
--- /dev/null
+++ b/timeoutswitchingfilehandler.py
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+import logging
+import threading
+import time
+
+class TimeoutSwitchingFileHandler(logging.Handler):
+    def __init__(self, filename, min_timeout=60, max_timeout=3600):
+        super().__init__()
+        self.basename = filename
+        self.min_timeout = min_timeout
+        self.max_timeout = max_timeout
+        self.fh = None
+        self.last_emit = 0
+        self.first_emit = 0
+        self.last_emit = 0
+        cleanup = threading.Thread(target=self.cleanup_loop, daemon=True)
+        cleanup.start()
+
+    def emit(self, record):
+        msg = self.format(record)
+        now = time.time()
+        if not self.fh:
+            now_tm = time.localtime(now)
+            filename = self.basename + time.strftime("%Y-%m-%d-%H-%M-%S", now_tm) + "-%06d" % (now % 1 * 1000000) + ".log"
+            self.fh = open(filename, "a")
+            self.first_emit = now
+        self.fh.write(msg)
+        self.fh.write("\n")
+        self.fh.flush()
+        self.last_emit = now
+
+    def cleanup_loop(self):
+        while True:
+            time.sleep(1)
+            self.acquire()
+            now = time.time()
+            if self.fh and now - self.last_emit > self.min_timeout:
+                self.fh.close()
+                self.fh = None
+            if self.fh and now - self.first_emit > self.max_timeout:
+                self.fh.close()
+                self.fh = None
+            self.release()