From 38dec7a60e6c6329b062c1d30e37fac55a86706a Mon Sep 17 00:00:00 2001
From: Ryan Mahoney <ryan.mahoney@outlook.com>
Date: Thu, 5 Sep 2019 11:33:41 -0400
Subject: [PATCH] cache realtime data, reduce TNM polling time (#197)

---
 .../ts/tnm/components/TransitNearMe.tsx       |  2 +-
 apps/site/lib/site/application.ex             |  3 ++-
 apps/site/lib/site/realtime_schedule.ex       | 22 +++++++++++++------
 apps/site/mix.exs                             |  3 ++-
 .../site/test/site/realtime_schedule_test.exs |  1 +
 5 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/apps/site/assets/ts/tnm/components/TransitNearMe.tsx b/apps/site/assets/ts/tnm/components/TransitNearMe.tsx
index 28238388a2..aa38d61af3 100644
--- a/apps/site/assets/ts/tnm/components/TransitNearMe.tsx
+++ b/apps/site/assets/ts/tnm/components/TransitNearMe.tsx
@@ -148,7 +148,7 @@ const TransitNearMe = ({
         stopsWithDistances.stops.map(stop => stop.id),
         dispatch
       ),
-    45000
+    30000
   );
 
   return (
diff --git a/apps/site/lib/site/application.ex b/apps/site/lib/site/application.ex
index 799e993be7..40d8580dd6 100644
--- a/apps/site/lib/site/application.ex
+++ b/apps/site/lib/site/application.ex
@@ -18,7 +18,8 @@ defmodule Site.Application do
       supervisor(SiteWeb.Endpoint, []),
       supervisor(Site.GreenLine.Supervisor, []),
       supervisor(Site.Stream.Vehicles, []),
-      supervisor(Site.React, [])
+      supervisor(Site.React, []),
+      supervisor(Site.RealtimeSchedule, [])
     ]
 
     # See http://elixir-lang.org/docs/stable/elixir/Supervisor.html
diff --git a/apps/site/lib/site/realtime_schedule.ex b/apps/site/lib/site/realtime_schedule.ex
index 6a1c1da34b..a8a4b7854c 100644
--- a/apps/site/lib/site/realtime_schedule.ex
+++ b/apps/site/lib/site/realtime_schedule.ex
@@ -7,6 +7,8 @@ defmodule Site.RealtimeSchedule do
       are considering route patterns with the same name to be effectively the same
   """
 
+  use RepoCache, ttl: :timer.seconds(30)
+
   alias Predictions.Prediction
   alias Predictions.Repo, as: PredictionsRepo
   alias RoutePatterns.RoutePattern
@@ -42,6 +44,13 @@ defmodule Site.RealtimeSchedule do
 
   @spec stop_data([Stop.id_t()], DateTime.t(), Keyword.t()) :: [map]
   def stop_data(stop_ids, now, opts \\ []) do
+    cache(stop_ids, fn _ ->
+      do_stop_data(stop_ids, now, opts)
+    end)
+  end
+
+  @spec do_stop_data([Stop.id_t()], DateTime.t(), Keyword.t()) :: [map]
+  defp do_stop_data(stop_ids, now, opts) do
     opts = Keyword.merge(@default_opts, opts)
     stops_fn = Keyword.fetch!(opts, :stops_fn)
     routes_fn = Keyword.fetch!(opts, :routes_fn)
@@ -49,22 +58,21 @@ defmodule Site.RealtimeSchedule do
     schedules_fn = Keyword.fetch!(opts, :schedules_fn)
     alerts_fn = Keyword.fetch!(opts, :alerts_fn)
 
-    # stage 1, get stops and routes
-    stops_task = Task.async(fn -> get_stops(stop_ids, stops_fn) end)
+    # stage 1, get routes
     routes_task = Task.async(fn -> get_routes(stop_ids, routes_fn) end)
-    [stops, route_with_patterns] = Enum.map([stops_task, routes_task], &Task.await/1)
+    route_with_patterns = Task.await(routes_task)
 
-    # stage 2, get predictions, schedules, and alerts
+    # stage 2, get stops, predictions, schedules, and alerts
+    stops_task = Task.async(fn -> get_stops(stop_ids, stops_fn) end)
     predictions_task = Task.async(fn -> get_predictions(route_with_patterns, predictions_fn) end)
-
     schedules_task = Task.async(fn -> get_schedules(route_with_patterns, now, schedules_fn) end)
 
     alert_counts_task =
       Task.async(fn -> get_alert_counts(route_with_patterns, now, alerts_fn) end)
 
-    [predictions, schedules, alert_counts] =
+    [stops, predictions, schedules, alert_counts] =
       Enum.map(
-        [predictions_task, schedules_task, alert_counts_task],
+        [stops_task, predictions_task, schedules_task, alert_counts_task],
         &Task.await(&1, @long_timeout)
       )
 
diff --git a/apps/site/mix.exs b/apps/site/mix.exs
index 6a66cc81d5..27c8999db9 100644
--- a/apps/site/mix.exs
+++ b/apps/site/mix.exs
@@ -126,7 +126,8 @@ defmodule Site.Mixfile do
       {:predictions, in_umbrella: true},
       {:trip_plan, in_umbrella: true},
       {:services, in_umbrella: true},
-      {:route_patterns, in_umbrella: true}
+      {:route_patterns, in_umbrella: true},
+      {:repo_cache, in_umbrella: true}
     ]
   end
 end
diff --git a/apps/site/test/site/realtime_schedule_test.exs b/apps/site/test/site/realtime_schedule_test.exs
index bd37e3e5cc..d1e4e5cd60 100644
--- a/apps/site/test/site/realtime_schedule_test.exs
+++ b/apps/site/test/site/realtime_schedule_test.exs
@@ -252,6 +252,7 @@ defmodule Site.RealtimeScheduleTest do
       }
     ]
 
+    RealtimeSchedule.clear_cache()
     actual = RealtimeSchedule.stop_data(stops, @now, opts)
 
     assert actual == expected