Add data source health monitoring via an extension.

Refs: #379, #415

redash/monitor.py

@@ -35,7 +35,7 @@ def get_queues_status():
             'data_sources': ', '.join(sources),
             'size': redis_connection.llen(queue)
         }
-    
+
     queues['celery'] = {
         'size': redis_connection.llen('celery'),
         'data_sources': ''

redash/worker.py

@@ -78,3 +78,10 @@ def __call__(self, *args, **kwargs):
 def init_celery_flask_app(**kwargs):
     app = create_app()
     app.app_context().push()
+
+@celery.on_after_configure.connect
+def add_periodic_tasks(sender, **kwargs):
+    app = create_app()
+    periodic_tasks = getattr(app, 'periodic_tasks', {})
+    for params in periodic_tasks.values():
+        sender.add_periodic_task(**params)

requirements.txt

@@ -54,4 +54,4 @@ disposable-email-domains
 # Uncomment the requirement for ldap3 if using ldap.
 # It is not included by default because of the GPL license conflict.
 # ldap3==2.2.4
-redash-stmo>=2018.4.0
+redash-stmo>=2018.8.1