implement parent monitoring thread (#8)

src/jsi/cli.py

@@ -28,7 +28,7 @@
 
 Less common options:
   --output DIRECTORY  directory where solver output files will be written
-  --supervisor        run a supervisor process to avoid orphaned subprocesses
+  --reaper            run a reaper process that kills orphaned solvers when jsi exits
   --debug             enable debug logging
   --csv               print solver results in CSV format (<output>/<input>.csv)
   --perf              print performance timers
@@ -53,6 +53,7 @@
 import signal
 import sys
 import threading
+import time
 from functools import partial
 
 from jsi.config.loader import Config, find_available_solvers, load_definitions
@@ -134,6 +135,38 @@ def cleanup():
     atexit.register(cleanup)
 
 
+def monitor_parent():
+    """
+    Monitor the parent process and exit if it dies or changes.
+
+    Caveats:
+    - only works on POSIX systems
+    - only works if called early enough (before the original parent process exits)
+    """
+
+    parent_pid = os.getppid()
+
+    def check_parent():
+        while True:
+            try:
+                current_ppid = os.getppid()
+
+                # if parent PID changed (original parent died), we exit
+                if current_ppid != parent_pid or current_ppid == 1:
+                    stderr.print("parent process died, exiting...")
+                    os.kill(os.getpid(), signal.SIGTERM)
+                    break
+                time.sleep(1)  # check every second
+            except ProcessLookupError:
+                # if we can't check parent PID, assume parent died
+                os.kill(os.getpid(), signal.SIGTERM)
+                break
+
+    # Start monitoring in background thread
+    monitor_thread = threading.Thread(target=check_parent, daemon=True)
+    monitor_thread.start()
+
+
 class BadParameterError(Exception):
     pass
 
@@ -174,8 +207,8 @@ def parse_args(args: list[str]) -> Config:
                 config.model = True
             case "--csv":
                 config.csv = True
-            case "--supervisor":
-                config.supervisor = True
+            case "--reaper":
+                config.reaper = True
             case "--daemon":
                 config.daemon = True
             case "--timeout":
@@ -229,6 +262,9 @@ def main(args: list[str] | None = None) -> int:
     global stdout
     global stderr
 
+    # kick off the parent monitor in the background as early as possible
+    monitor_parent()
+
     if args is None:
         args = sys.argv[1:]
 
@@ -310,8 +346,8 @@ def main(args: list[str] | None = None) -> int:
         controller.start()
         status.start()
 
-        if config.supervisor:
-            from jsi.supervisor import Supervisor
+        if config.reaper:
+            from jsi.reaper import Reaper
 
             # wait for the subprocesses to start, we need the PIDs for the supervisor
             while controller.task.status.value < TaskStatus.RUNNING.value:
@@ -320,9 +356,9 @@ def main(args: list[str] | None = None) -> int:
             # start a supervisor process in daemon mode so that it does not block
             # the program from exiting
             child_pids = [command.pid for command in controller.commands]
-            sv = Supervisor(os.getpid(), child_pids, config)
-            sv.daemon = True
-            sv.start()
+            reaper = Reaper(os.getpid(), child_pids, config.debug)
+            reaper.daemon = True
+            reaper.start()
 
         # wait for the solvers to finish
         controller.join()

src/jsi/config/loader.py

@@ -24,7 +24,7 @@ def __init__(
         debug: bool = False,
         input_file: str | None = None,
         output_dir: str | None = None,
-        supervisor: bool = False,
+        reaper: bool = False,
         sequence: Sequence[str] | None = None,
         model: bool = False,
         csv: bool = False,
@@ -36,7 +36,7 @@ def __init__(
         self.debug = debug
         self.input_file = input_file
         self.output_dir = output_dir
-        self.supervisor = supervisor
+        self.reaper = reaper
         self.sequence = sequence
         self.model = model
         self.csv = csv

src/jsi/supervisor.py → src/jsi/reaper.py

@@ -1,30 +1,30 @@
 import multiprocessing
+import sys
 import time
 
-from jsi.core import Config
-from jsi.utils import LogLevel, kill_process, logger, pid_exists
+from jsi.utils import LogLevel, get_console, kill_process, logger, pid_exists
 
 
-class Supervisor(multiprocessing.Process):
-    """Supervisor process that monitors the parent process and its children."""
+class Reaper(multiprocessing.Process):
+    """Reaper process that monitors the parent process and its children."""
 
     parent_pid: int
     child_pids: list[int]
-    config: Config
+    debug: bool
 
-    def __init__(self, parent_pid: int, child_pids: list[int], config: Config):
+    def __init__(self, parent_pid: int, child_pids: list[int], debug: bool = False):
         super().__init__()
         self.parent_pid = parent_pid
         self.child_pids = child_pids
-        self.config = config
+        self.debug = debug
 
     def run(self):
-        if self.config.debug:
-            logger.enable(console=self.config.stderr, level=LogLevel.DEBUG)
+        level = LogLevel.DEBUG if self.debug else LogLevel.INFO
+        logger.enable(console=get_console(sys.stderr), level=level)
 
-        logger.debug(f"supervisor started (PID: {self.pid})")
-        logger.debug(f"watching parent (PID: {self.parent_pid})")
-        logger.debug(f"watching children (PID: {self.child_pids})")
+        logger.info(f"reaper started (PID: {self.pid})")
+        logger.info(f"watching parent (PID: {self.parent_pid})")
+        logger.info(f"watching children (PID: {self.child_pids})")
 
         last_message_time = time.time()
         try:

src/jsi/server.py

@@ -206,9 +206,11 @@ def sync_solve(self, file: str) -> str:
 
         listener = ResultListener()
         controller = ProcessController(
-            task, commands, self.config,
+            task,
+            commands,
+            self.config,
             start_callback=start_logger,
-            exit_callback=listener.exit_callback
+            exit_callback=listener.exit_callback,
         )
         controller.start()
 

tests/test_process_control.py

@@ -66,7 +66,7 @@ def test_real_process():
 def test_cmd():
     command = cmd()
     command.start()
-    stdout, stderr = command.communicate(timeout=0.1)
+    stdout, stderr = command.communicate(timeout=0.2)
 
     assert command.returncode == 0
     assert not stdout