Fix non-graceful server shutdowns and improve signal handling (#41)

* fix: replace os.system() with subprocess.call()

https://docs.python.org/3/library/subprocess.html#replacing-os-system
os.system() ignores SIGINT, which is the stop signal set by the Dockerfile.
This fix should immediately kill the Reforger process upon being asked to stop.

* feat: send SIGTERM to reforger when stopping

This provides a chance for the Reforger process to cleanup.

* feat: kill Reforger process on unhandled exception

If an unknown exception or a second interrupt occurs,
ensure the process is killed.

* feat: propagate exit code from Reforger process

* feat: handle SIGTERM on launch.py

This allows omitting STOPSIGNAL from Dockerfile.

* fix: use shlex.join() when printing command

This ensures the command can actually be invoked by the user
in case some of the arguments contain whitespace or other
unsafe characters.

* fix: stop reforger using SIGINT instead of SIGTERM

* refactor: explicitly skip kill clause when raising SystemExit

The purpose of this is making the program flow more obvious,
since proc.kill() already does nothing on completed processes.

Author: thegamecracks

launch.py

@@ -2,9 +2,15 @@
 import os
 import random
 import re
+import shlex
+import signal
 import subprocess
+import sys
 from pathlib import Path
 
+# On SIGTERM, raise KeyboardInterrupt instead of exiting abruptly.
+signal.signal(signal.SIGTERM, signal.default_int_handler)
+
 CONFIG_GENERATED = "/reforger/Configs/docker_generated.json"
 
 
@@ -236,18 +242,35 @@ def bool_str(text):
 
     config_path = CONFIG_GENERATED
 
-launch = " ".join(
-    [
-        os.environ["ARMA_BINARY"],
-        f"-config {config_path}",
-        "-backendlog",
-        "-nothrow",
-        f"-maxFPS {os.environ['ARMA_MAX_FPS']}",
-        f"-profile {os.environ['ARMA_PROFILE']}",
-        f"-addonDownloadDir {os.environ['ARMA_WORKSHOP_DIR']}",
-        f"-addonsDir {os.environ['ARMA_WORKSHOP_DIR']}",
-        os.environ["ARMA_PARAMS"],
-    ]
-)
-print(launch, flush=True)
-os.system(launch)
+launch = [
+    os.environ["ARMA_BINARY"],
+    "-config",
+    config_path,
+    "-backendlog",
+    "-nothrow",
+    "-maxFPS",
+    os.environ["ARMA_MAX_FPS"],
+    "-profile",
+    os.environ["ARMA_PROFILE"],
+    "-addonDownloadDir",
+    os.environ["ARMA_WORKSHOP_DIR"],
+    "-addonsDir",
+    os.environ["ARMA_WORKSHOP_DIR"],
+    *shlex.split(os.environ["ARMA_PARAMS"]),
+]
+
+print(shlex.join(launch), flush=True)
+
+proc = subprocess.Popen(launch)
+
+try:
+    try:
+        sys.exit(proc.wait())
+    except KeyboardInterrupt:
+        proc.send_signal(signal.SIGINT)
+        sys.exit(proc.wait())
+except SystemExit:
+    raise
+except BaseException:
+    proc.kill()
+    raise