Handle SIGTERM for cleaner shutdowns (#737)

changedetection.py

@@ -6,6 +6,34 @@
 # Read more https://github.com/dgtlmoon/changedetection.io/wiki
 
 from changedetectionio import changedetection
+import multiprocessing
+import signal
+import os
+
+def sigterm_handler(_signo, _stack_frame):
+    import sys
+    print('Shutdown: Got SIGCHLD')
+    # https://stackoverflow.com/questions/40453496/python-multiprocessing-capturing-signals-to-restart-child-processes-or-shut-do
+    pid, status = os.waitpid(-1, os.WNOHANG | os.WUNTRACED | os.WCONTINUED)
+
+    print('Sub-process: pid %d status %d' % (pid, status))
+    if status != 0:
+        sys.exit(1)
+
+    raise SystemExit
 
 if __name__ == '__main__':
-    changedetection.main()
+    signal.signal(signal.SIGCHLD, sigterm_handler)
+    # The only way I could find to get Flask to shutdown, is to wrap it and then rely on the subsystem issuing SIGTERM/SIGKILL
+    parse_process = multiprocessing.Process(target=changedetection.main)
+    parse_process.daemon = True
+    parse_process.start()
+    import time
+
+    try:
+        while True:
+            time.sleep(1)
+
+    except KeyboardInterrupt:
+        #parse_process.terminate() not needed, because this process will issue it to the sub-process anyway
+        print ("Exited - CTRL+C")

changedetectionio/__init__.py

@@ -1259,7 +1259,6 @@ def notification_runner():
     global notification_debug_log
     from datetime import datetime
     import json
-
     while not app.config.exit.is_set():
         try:
             # At the moment only one thread runs (single runner)

changedetectionio/changedetection.py

@@ -4,6 +4,7 @@
 
 import getopt
 import os
+import signal
 import sys
 
 import eventlet
@@ -11,7 +12,22 @@ import eventlet.wsgi
 from . import store, changedetection_app, content_fetcher
 from . import __version__
 
+# Only global so we can access it in the signal handler
+datastore = None
+app = None
+
+def sigterm_handler(_signo, _stack_frame):
+    global app
+    global datastore
+
+    app.config.exit.set()
+    datastore.sync_to_json()
+    print('Shutdown: Got SIGTERM, DB saved to disk')
+    raise SystemExit
+
 def main():
+    global datastore
+    global app
     ssl_mode = False
     host = ''
     port = os.environ.get('PORT') or 5000
@@ -72,8 +88,10 @@ def main():
                 "Or use the -C parameter to create the directory.".format(app_config['datastore_path']), file=sys.stderr)
             sys.exit(2)
 
+
     datastore = store.ChangeDetectionStore(datastore_path=app_config['datastore_path'], version_tag=__version__)
     app = changedetection_app(app_config, datastore)
+    signal.signal(signal.SIGTERM, sigterm_handler)
 
     # Go into cleanup mode
     if do_cleanup:
@@ -111,4 +129,3 @@ def main():
     else:
         eventlet.wsgi.server(eventlet.listen((host, int(port))), app)
 
-