Support Windows 7 with Python 3.8

README.md

@@ -1,6 +1,14 @@
 # Network spike monitor
 
-Windows 10/11, Python 3.10 or newer. No packages or administrator rights required.
+Windows 7 SP1 or newer, Python 3.8 or newer (use Python 3.8 on Windows 7). No packages or administrator rights required to run the monitor.
+
+### Windows 7 setup
+
+Install [Python 3.8.10](https://www.python.org/downloads/release/python-3810/) using its **Windows installer (32-bit)** or **Windows installer (64-bit)** to match your system. Select **Add Python 3.8 to PATH** during installation, then open a new command prompt. Use the traditional installer listed under Files, not the newer Python install manager. Python 3.8 is the last branch compatible with Windows 7; 3.8.10 is its last release with official Windows installers. Windows 7 must have Service Pack 1 and the updates needed by the Python installer.
+
+Check `python --version` reports Python 3.8.x on Windows 7. On newer Windows, a newer supported Python release is fine. The monitor's ping and tracert options, trace cancellation, and logging use Python 3.8-compatible APIs. Python 3.8 is no longer maintained. Compatibility tests run on Python 3.8 on a newer Windows system; a physical Windows 7 installation has not been tested.
+
+### Start monitoring
 
 Double-click **Start Monitor.cmd**, or run:
 

network_monitor.py

@@ -1,4 +1,4 @@
-"""Windows ping spike monitor. Python 3.10+, standard library only."""
+"""Windows ping spike monitor. Python 3.8+, standard library only."""
 from __future__ import annotations
 
 import argparse
@@ -376,7 +376,11 @@ def main():
         log.write("error", f"Error: {error}", error=str(error))
     finally:
         stop.set()
-        executor.shutdown(wait=True, cancel_futures=True)
+        # Python 3.8 has no shutdown(cancel_futures=...). There is at most
+        # one submitted trace; cancel it if queued, or let stop end it if running.
+        if pending is not None:
+            pending.cancel()
+        executor.shutdown(wait=True)
         log.write("stop", "Monitor stopped.", samples=samples)
         log.file.close()
     return 1 if failed else 0

test_network_monitor.py

@@ -1,6 +1,7 @@
 import pathlib
 import json
 import sys
+import subprocess
 import tempfile
 import threading
 import unittest
@@ -11,6 +12,24 @@ from network_monitor import Detector, analyze_trace, parse_ping, parse_trace, ru
 
 
 class MonitorTests(unittest.TestCase):
+    @unittest.skipUnless(sys.platform == "win32", "requires Windows ping and tracert")
+    def test_main_finishes_diagnostic_and_closes_log(self):
+        # Exercise real executor shutdown on the interpreter running the suite,
+        # including Python 3.8, where cancel_futures is unavailable.
+        with tempfile.TemporaryDirectory() as directory:
+            result = subprocess.run(
+                [sys.executable, str(pathlib.Path(__file__).with_name("network_monitor.py")),
+                 "--target", "127.0.0.1", "--count", "1", "--trace-now",
+                 "--log-dir", directory],
+                stdout=subprocess.PIPE, stderr=subprocess.STDOUT, timeout=20)
+            self.assertEqual(result.returncode, 0, result.stdout.decode(errors="replace"))
+            entries = [json.loads(line) for line in
+                       (pathlib.Path(directory) / "events.jsonl").read_text().splitlines()]
+            self.assertEqual(entries[-1]["event"], "stop")
+            self.assertEqual(entries[-1]["samples"], 1)
+            self.assertTrue(any(entry["event"] == "trace_complete" for entry in entries))
+            self.assertFalse(any(entry["event"] == "error" for entry in entries))
+
     def test_only_bad_pings_are_logged(self):
         with tempfile.TemporaryDirectory() as directory:
             log = Log(pathlib.Path(directory))