Add a pid file to avoid running honcho multiple times

sith/composer.py

@@ -1,26 +1,68 @@
-import os
+import logging
 import signal
 import subprocess
 import sys
 
 import psutil
 
-COMPOSER_PID = "COMPOSER_PID"
+from sith import settings
+
+
+def get_pid() -> int | None:
+    """Read the PID file to get the currently running composer if it exists"""
+    if not settings.COMPOSER_PID_PATH.exists():
+        return None
+    with open(settings.COMPOSER_PID_PATH, "r", encoding="utf8") as f:
+        return int(f.read())
+
+
+def write_pid(pid: int):
+    """Write currently running composer pid in PID file"""
+    if not settings.COMPOSER_PID_PATH.exists():
+        settings.COMPOSER_PID_PATH.parent.mkdir(parents=True, exist_ok=True)
+    with open(settings.COMPOSER_PID_PATH, "w", encoding="utf8") as f:
+        _ = f.write(str(pid))
+
+
+def delete_pid():
+    """Delete PID file for cleanup"""
+    settings.COMPOSER_PID_PATH.unlink(missing_ok=True)
+
+
+def is_composer_running() -> bool:
+    """Check if the process in the PID file is running"""
+    pid = get_pid()
+    if pid is None:
+        return False
+    try:
+        return psutil.Process(pid).is_running()
+    except psutil.NoSuchProcess:
+        return False
 
 
 def start_composer(procfile: str):
     """Starts the composer and stores the PID as an environment variable
     This allows for running smoothly with the django reloader
     """
+    if is_composer_running():
+        logging.info(f"Composer is already running with pid {get_pid()}")
+        logging.info(
+            f"If this is a mistake, please delete {settings.COMPOSER_PID_PATH} and restart the process"
+        )
+        return
     process = subprocess.Popen(
         [sys.executable, "-m", "honcho", "-f", procfile, "start"],
     )
-    os.environ[COMPOSER_PID] = str(process.pid)
+    write_pid(process.pid)
 
 
 def stop_composer():
     """Stops the composer if it was started before"""
-    if (pid := os.environ.get(COMPOSER_PID, None)) is not None:
-        process = psutil.Process(int(pid))
+    if is_composer_running():
+        process = psutil.Process(get_pid())
+        if process.parent() != psutil.Process():
+            logging.info("Currently running composer is controlled by another process")
+            return
         process.send_signal(signal.SIGTERM)
-        process.wait()
+        _ = process.wait()
+        delete_pid()