[staged-updates] v2, removes that database query entirely, we just we…

…re not using the cached value.

database/user_models_participant.py

@@ -255,43 +255,6 @@ def log(self, action: str):
     ################################################################################################
     ################################## PARTICIPANT STATE ###########################################
     ################################################################################################
-    # FIXME: make this a cached value
-
-    @property
-    def last_app_heartbeat(self) -> Optional[datetime]:
-        """ Returns the last time the app sent a heartbeat. 
-        `self.heartbeats.latest("timestamp")` emits the following SQL:
-            SELECT "database_appheartbeats"."id",
-            "database_appheartbeats"."participant_id",
-            "database_appheartbeats"."timestamp",
-            "database_appheartbeats"."message"
-            FROM "database_appheartbeats"
-            WHERE "database_appheartbeats"."participant_id" = 8051
-            ORDER BY "database_appheartbeats"."timestamp" DESC
-            LIMIT 1
-        This is slow because it is... slow.
-        
-        `self.heartbeats.aggregate(min=Min("timestamp"))` emits
-            SELECT MIN("database_appheartbeats"."timestamp") AS "min"
-            FROM "database_appheartbeats"
-            WHERE "database_appheartbeats"."participant_id" = 8051
-        is like 10x faster but still too slow, the where clause is probably not using the index?
-        
-        Current implementation:
-        `.values_list("heartbeats__timestamp").aggregate(min=Min("heartbeats__timestamp"))` emits
-            SELECT MIN("database_appheartbeats"."timestamp") AS "min"
-            FROM "database_participant"
-            LEFT OUTER JOIN "database_appheartbeats"
-              ON ("database_participant"."id" = "database_appheartbeats"."participant_id")
-            WHERE "database_participant"."id" = 8051
-        
-        This can take 10ms, it seems to get cached.
-        """
-        return (
-            Participant.objects.filter(id=self.id)
-            .values_list("heartbeats__timestamp")
-            .aggregate(min=Min("heartbeats__timestamp"))['min']
-        )
 
     @property
     def is_active_one_week(self) -> bool:
@@ -551,7 +514,7 @@ def summary(cls):
 class AppHeartbeats(UtilityModel):
     """ Storing heartbeats is intended as a debugging tool for monitoring app uptime, the idea is 
     that the app checks in every 5 minutes so we can see when it doesn't. (And then send it a push
-    notification)  """
+    notification) """
     participant = models.ForeignKey(Participant, null=False, on_delete=models.PROTECT, related_name="heartbeats")
     timestamp = models.DateTimeField(null=False, blank=False, db_index=True)
     # TODO: message is not intended to be surfaced to anyone other than developers, at time of comment
@@ -560,6 +523,7 @@ class AppHeartbeats(UtilityModel):
 
     @classmethod
     def create(cls, participant: Participant, timestamp: datetime, message: str = None):
+        participant.update_only(last_heartbeat_checkin=timestamp)
         return cls.objects.create(participant=participant, timestamp=timestamp, message=message)
 
 

endpoints/mobile_endpoints.py

@@ -306,8 +306,8 @@ def mobile_heartbeat(request: ParticipantRequest, OS_API=""):
     This endpoint is hit every 5 minutes by the app, at time of writing it is ios-only.  """
     # a field on the participant model is WAY easier to deal with when querying data for push notifications
     now = timezone.now()
-    request.session_participant.update_only(last_heartbeat_checkin=now)
     # AppHeartbeats is the historical record of app checkins.
+    # .create updates the field on the participant.
     AppHeartbeats.create(participant=request.session_participant, timestamp=now,
                          message = request.POST.get("message", None))
     return HttpResponse(status=200)

frontend/templates/participant.html

@@ -68,7 +68,7 @@ <h3 class="text-center"> <b>Activity Information </b></h3>
       </tr>
       <tr>
         <td><b>Last Heartbeat</b></td>
-        <td>{{ really_nice_time_format_with_tz(participant_last_app_heartbeat, study_timezone) }}</td>
+        <td>{{ really_nice_time_format_with_tz(participant.last_heartbeat_checkin, study_timezone) }}</td>
       </tr>
       <tr>
         <td><b>Last check-in for updated surveys</b></td>

libs/endpoint_helpers/participant_helpers.py

@@ -53,7 +53,6 @@ def render_participant_page(request: ResearcherRequest, participant: Participant
     )
 
     conditionally_display_locked_message(request, participant)
-    last_app_heartbeat = participant.last_app_heartbeat
     study_interventions_exists = study.interventions.exists()
     study_fields_exists = study.fields.exists()
     relation = request.session_researcher.get_study_relation(study.id)
@@ -76,7 +75,6 @@ def render_participant_page(request: ResearcherRequest, participant: Participant
             locked=participant.is_dead,
             can_delete=can_delete,
             study_timezone=participant.study.timezone,
-            participant_last_app_heartbeat=last_app_heartbeat,
             study_interventions_exists=study_interventions_exists,
             study_fields_exists=study_fields_exists,
         )

libs/utils/http_utils.py

@@ -1,6 +1,6 @@
 import functools
 from datetime import datetime, tzinfo
-from typing import Callable, Dict, List, Union
+from typing import Callable, Dict, List, Optional, Union
 
 from dateutil import tz
 from django.http.request import HttpRequest
@@ -39,7 +39,7 @@ def nice_iso_time_format(dt: datetime, timezone: Union[tzinfo, str]) -> str:
     return final_dt.strftime('%A %Y-%m-%d, %-I:%M %p')
 
 
-def really_nice_time_format_with_tz(dt: datetime, timezone: Union[tzinfo, str]) -> str:
+def really_nice_time_format_with_tz(dt: Optional[datetime], timezone: Union[tzinfo, str]) -> str:
     """ output looks like Tuesday Aug 25, 2020, 4:31 PM (EST) """
     if dt is None:
         return ""