Add celery tasks to listen to postgres NOTIFY

geotrek/common/tasks.py

@@ -1,10 +1,12 @@
+import asyncio
 import importlib
 
 from os.path import join
 import sys
 from celery import Task, shared_task, current_task
 from django.contrib.auth.models import User
 from django.conf import settings
+from django.db import connections
 from django.utils.translation import gettext_lazy as _
 
 
@@ -123,3 +125,39 @@
         'report': parser.report(output_format='html').replace('$celery_id', current_task.request.id),
         'name': current_task.name
     }
+
+
+@shared_task(name='geotrek.common.handle_notification')
+def handle_notification(channel, payload):
+    print("Do something long......")
+    print(f"I have treated {channel} {payload}")
+
+
+async def read_async(connection):
+
+    loop = asyncio.get_running_loop()
+    q = asyncio.Queue()
+
+    def put_notification_in_queue():
+        connection.poll()
+        data = connection.notifies.pop(0)
+        q.put_nowait(data)
+
+    loop.add_reader(connection, put_notification_in_queue)
+
+    while 1:
+        notified = await q.get()
+        print("Notification received: " + str(notified))
+        # TODO we need to some nother celery workers to take on in these tasks
+        # Because at the moment our only celery worker is stuck doing 'await q.get()'
+        handle_notification.delay(notified.channel, notified.payload)
+
+
+@shared_task(name='geotrek.common.listen_to_notifications')
+def listen_to_notifications():
+    notifications_connection = connections.create_connection('default')
+    notifications_connection.connect()
+    curs = notifications_connection.cursor()
+    curs.execute("LISTEN testchannel;")
+    # TODO Close this connection properly
+    asyncio.run(read_async(notifications_connection.connection))