Add monitoring for app connections to the db (#2235)

events/event_source.py

@@ -72,7 +72,9 @@ class PostgresEventSource(EventSource):
                     Session.close()  # Ensure we get a new connection and we don't leave a dangling tx
 
     def __connect(self):
-        self.__connection = psycopg2.connect(self.__connection_string)
+        self.__connection = psycopg2.connect(
+            self.__connection_string, application_name="sl-event-listen"
+        )
 
         from app.db import Session
 

monitoring.py

@@ -94,6 +94,20 @@ def log_nb_db_connection():
     newrelic.agent.record_custom_metric("Custom/nb_db_connections", nb_connection)
 
 
+@newrelic.agent.background_task()
+def log_nb_db_connection_by_app_name():
+    # get the number of connections to the DB
+    rows = Session.execute(
+        "SELECT application_name, count(datid) FROM pg_stat_activity group by application_name"
+    )
+    for row in rows:
+        if row[0].find("sl-") == 0:
+            LOG.d("number of db connections for app %s = %s", row[0], row[1])
+            newrelic.agent.record_custom_metric(
+                f"Custom/nb_db_app_connection/{row[0]}", row[1]
+            )
+
+
 @newrelic.agent.background_task()
 def log_pending_to_process_events():
     r = Session.execute("select count(*) from sync_event WHERE taken_time IS NULL;")
@@ -148,6 +162,7 @@ if __name__ == "__main__":
         log_pending_to_process_events()
         log_events_pending_dead_letter()
         log_failed_events()
+        log_nb_db_connection_by_app_name()
         Session.close()
 
         exporter.run()