Background services without systemd (runit, OpenRC, ...)

Co-Authored-By: Claude Opus 5.5 <[email protected]>

Programs/ServiceRun.py

@@ -1,33 +1,104 @@
-"""Runs a SaraSuite program as a background service on Windows, the stand-in
-for a systemd --user service. Started windowless with pythonw.exe, both at
-login (by the program's shortcut in the Startup folder) and when SaraSuite
-or the program's own GUI (e.g. SaraSort for SaraSortd) starts it:
+"""Runs a SaraSuite program as a background service where there's no systemd
+--user to do it: on Windows (started windowless with pythonw.exe), and on
+Linux with another init system (runit on Void, OpenRC, s6, dinit, ...).
+Started at login (Windows: a shortcut in the Startup folder; Linux: an XDG
+autostart entry) and when SaraSuite or the program's own GUI (e.g. SaraSort
+for SaraSortd) starts it:
 
-    pythonw.exe ServiceRun.py <Name> <Script>       (in the service's working folder)
+    python ServiceRun.py <Name> <Script> [<WorkingDir>]
 
-It records its PID in %LOCALAPPDATA%\\SaraSuite\\Services\\<Name>.pid, so
-anything can tell whether the service runs, and stop it (taskkill), without
-a Windows service and without admin rights. Installed next to each program
-that has a Windows service (Programs/<Name>/Manifest.toml, [[Services]]).
+Like the systemd unit it stands in for: one copy at a time; restarted 10
+seconds after it fails (an exception or a non-zero exit), not after a clean
+exit or a stop; its output goes to <Name>.log. Its PID is in <Name>.pid, so
+anything can tell whether it runs, and stop it, without admin rights. Both
+files are in SaraSuite's Services folder: %LOCALAPPDATA%\\SaraSuite\\Services
+on Windows, ~/.local/share/SaraSuite/Services on Linux.
+
+Installed next to each program that has a service (Programs/<Name>/Manifest.toml).
 """
 
 import os
 import runpy
+import signal
 import sys
+import time
+import traceback
+from datetime import datetime
 from pathlib import Path
 
+IsWindows = sys.platform == "win32"
+RestartSeconds = 10  # the unit's RestartSec
+MaxLogBytes = 1_000_000  # then the log starts over, the old one kept as <Name>.log.1
+Stopping = False
+
+
+def ServicesDir() -> Path:
+    if IsWindows:
+        Base = Path(os.environ.get("LOCALAPPDATA") or Path.home() / "AppData" / "Local")
+    else:
+        Base = Path(os.environ.get("XDG_DATA_HOME") or Path.home() / ".local" / "share")
+    return Base / "SaraSuite" / "Services"
+
+
+def _AlreadyRunning(PidFile: Path) -> bool:
+    """Linux: whether the PID file's process is another ServiceRun.py still
+    running (not a reused PID). Windows relies on whoever starts it to check."""
+    if IsWindows:
+        return False
+    try:
+        Pid = int(PidFile.read_text().strip())
+        if Pid == os.getpid():
+            return False
+        return b"ServiceRun.py" in Path(f"/proc/{Pid}/cmdline").read_bytes()
+    except (OSError, ValueError):
+        return False
+
+
+def _Stop(Signal, Frame) -> None:
+    global Stopping
+    Stopping = True
+    raise SystemExit(0)
+
 
 def Main() -> None:
     Name, Script = sys.argv[1], Path(sys.argv[2])
-    LocalAppData = Path(os.environ.get("LOCALAPPDATA") or Path.home() / "AppData" / "Local")
-    PidFile = LocalAppData / "SaraSuite" / "Services" / f"{Name}.pid"
-    PidFile.parent.mkdir(parents=True, exist_ok=True)
+    if len(sys.argv) > 3:
+        Folder = Path(sys.argv[3])
+        Folder.mkdir(parents=True, exist_ok=True)
+        os.chdir(Folder)
+    Folder = ServicesDir()
+    Folder.mkdir(parents=True, exist_ok=True)
+    # Not an f-string: SaraSuite fills in braced names like that one when it places this file.
+    PidFile = Folder / (Name + ".pid")
+    if _AlreadyRunning(PidFile):
+        return
+
+    LogFile = Folder / (Name + ".log")
+    if LogFile.exists() and LogFile.stat().st_size > MaxLogBytes:
+        LogFile.replace(LogFile.with_suffix(".log.1"))
+    sys.stdout = sys.stderr = open(LogFile, "a", buffering=1, encoding="utf-8", errors="replace")
+
     PidFile.write_text(str(os.getpid()))
+    if not IsWindows:
+        signal.signal(signal.SIGTERM, _Stop)  # a stop: finish cleanly, don't restart
+    sys.path.insert(0, str(Script.parent))
     try:
-        sys.argv = [str(Script)]
-        sys.path.insert(0, str(Script.parent))
-        runpy.run_path(str(Script), run_name="__main__")
+        while True:
+            print(f"== {datetime.now():%Y-%m-%d %H:%M:%S} starting {Script.name}")
+            try:
+                sys.argv = [str(Script)]
+                runpy.run_path(str(Script), run_name="__main__")
+                break
+            except SystemExit as Exit:
+                if Stopping or Exit.code in (None, 0):
+                    break
+                print(f"== {Script.name} exited with {Exit.code}")
+            except Exception:
+                traceback.print_exc()
+            print(f"== restarting in {RestartSeconds} seconds")
+            time.sleep(RestartSeconds)
     finally:
+        print(f"== {datetime.now():%Y-%m-%d %H:%M:%S} stopped")
         # Only remove it if it's still ours (a newer start may have replaced it).
         try:
             if PidFile.read_text().strip() == str(os.getpid()):