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

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

Services.py

@@ -0,0 +1,123 @@
+"""Background services SaraSuite runs itself, where there's no systemd --user
+to do it: Windows, and Linux with another init system (runit on Void, OpenRC,
+s6, dinit, ...). Each runs as Programs/ServiceRun.py <Name> <Script>
+<WorkingDir>, which keeps it going (restarts it if it fails), logs its output
+and records its PID, all in ServicesDir. At login it's started by
+- Windows: a shortcut in the Startup folder;
+- Linux: an XDG autostart entry (~/.config/autostart/<Name>.desktop), which
+  desktop sessions start whatever the init system is.
+The installer places those (Installer._ApplyStandInServices); this starts,
+stops and checks the services. SaraSort's Service.py does the same for SaraSortd.
+"""
+
+import os
+import re
+import signal
+import subprocess
+import time
+from pathlib import Path
+from typing import Callable, Optional
+
+from Core import ChildEnvironment, IsWindows, ServicesDir
+
+LogFn = Callable[[str], None]
+
+# Windows: child processes of a windowed program would each flash a console window.
+NoWindow = getattr(subprocess, "CREATE_NO_WINDOW", 0)
+_Detached = getattr(subprocess, "DETACHED_PROCESS", 0) | getattr(subprocess, "CREATE_NEW_PROCESS_GROUP", 0)
+
+
+def _PidFile(Name: str) -> Path:
+    return ServicesDir / f"{Name}.pid"
+
+
+def LogFile(Name: str) -> Path:
+    return ServicesDir / f"{Name}.log"
+
+
+def ServicePid(Name: str) -> Optional[int]:
+    """The PID ServiceRun.py recorded, if that process is still it."""
+    try:
+        Pid = int(_PidFile(Name).read_text().strip())
+    except (OSError, ValueError):
+        return None
+    if not IsWindows:
+        try:
+            return Pid if b"ServiceRun.py" in Path(f"/proc/{Pid}/cmdline").read_bytes() else None
+        except OSError:
+            return None
+    try:
+        Output = subprocess.run(
+            ["tasklist", "/FI", f"PID eq {Pid}", "/NH", "/FO", "CSV"],
+            capture_output=True, text=True, timeout=15, creationflags=NoWindow,
+        ).stdout
+    except (OSError, subprocess.SubprocessError):
+        return None
+    return Pid if re.search(rf'"{Pid}"', Output) else None
+
+
+def Command(Python: Path, Runner: Path, Name: str, Script: Path, WorkingDir: Path) -> list[str]:
+    """What runs the service (Python: pythonw.exe on Windows)."""
+    return [str(Python), str(Runner), Name, str(Script), str(WorkingDir)]
+
+
+def Start(Name: str, Python: Path, Runner: Path, Script: Path, WorkingDir: Path, Log: LogFn) -> None:
+    """Start a service now (it also starts at every login, the same way)."""
+    if ServicePid(Name) is not None:
+        Log(f"{Name} is already running")
+        return
+    WorkingDir.mkdir(parents=True, exist_ok=True)
+    Extra = {"creationflags": _Detached | NoWindow} if IsWindows else {"start_new_session": True}
+    subprocess.Popen(
+        Command(Python, Runner, Name, Script, WorkingDir), cwd=str(WorkingDir), env=ChildEnvironment(),
+        close_fds=True, stdin=subprocess.DEVNULL, stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL, **Extra,
+    )
+    Log(f"Started {Name}")
+
+
+def Stop(Name: str, Log: LogFn) -> None:
+    Pid = ServicePid(Name)
+    if Pid is not None:
+        if IsWindows:
+            subprocess.run(["taskkill", "/PID", str(Pid), "/T", "/F"], capture_output=True, creationflags=NoWindow)
+        else:
+            # ServiceRun.py finishes cleanly on SIGTERM; one that hangs is killed.
+            os.kill(Pid, signal.SIGTERM)
+            for _ in range(50):
+                if ServicePid(Name) is None:
+                    break
+                time.sleep(0.2)
+            else:
+                os.kill(Pid, signal.SIGKILL)
+        Log(f"Stopped {Name}")
+    _PidFile(Name).unlink(missing_ok=True)
+
+
+def Restart(Name: str, Python: Path, Runner: Path, Script: Path, WorkingDir: Path, Log: LogFn) -> None:
+    Stop(Name, Log)
+    Start(Name, Python, Runner, Script, WorkingDir, Log)
+
+
+def _ExecArgument(Text: str) -> str:
+    """One argument for a desktop entry's Exec key (the spec's quoting)."""
+    Text = Text.replace("%", "%%")
+    if re.fullmatch(r"[\w@%+=:,./-]+", Text):
+        return Text
+    return '"' + re.sub(r'(["`$\\])', r"\\\1", Text) + '"'
+
+
+def AutostartEntry(Name: str, Python: Path, Runner: Path, Script: Path, WorkingDir: Path) -> str:
+    """Linux: the XDG autostart entry that starts the service at login."""
+    Exec = " ".join(_ExecArgument(Part) for Part in Command(Python, Runner, Name, Script, WorkingDir))
+    return (
+        "# Written by SaraSuite: starts this background service at login on systems\n"
+        "# without systemd (runit, OpenRC, s6, ...). Removed with the program.\n"
+        "[Desktop Entry]\n"
+        "Type=Application\n"
+        f"Name={Name}\n"
+        f"Comment={Name} (background service, run by SaraSuite)\n"
+        f"Exec={Exec}\n"
+        "Terminal=false\n"
+        "NoDisplay=true\n"
+        "X-GNOME-Autostart-enabled=true\n"
+    )