Adding extra logging to celery tasks ans gunicorn, specifically log on SIGTERM and SIGINIT so that we can track better when an app restarts and why it restarts e.g. when it restarts after another signal.

app/celery/provider_tasks.py

@@ -1,3 +1,4 @@
+from celery.signals import worker_process_init, worker_process_shutdown, worker_shutdown
 from flask import current_app
 from notifications_utils.recipients import InvalidEmailError
 from sqlalchemy.orm.exc import NoResultFound
@@ -10,6 +11,11 @@ from app.statsd_decorators import statsd
 from app.delivery import send_to_providers
 
 
+@worker_process_shutdown.connect
+def worker_process_shutdown(sender, signal, pid, exitcode):
+    current_app.logger.info('Provider worker shutdown: PID: {} Exitcode: {}'.format(pid, exitcode))
+
+
 @notify_celery.task(bind=True, name="deliver_sms", max_retries=48, default_retry_delay=300)
 @statsd(namespace="tasks")
 def deliver_sms(self, notification_id):