Merge branch 'fix-broadcast-message-caching' into 'master'

Fix caching of future broadcast messages

Closes #36661

See merge request !13667

app/models/broadcast_message.rb

@@ -19,11 +19,21 @@ class BroadcastMessage < ActiveRecord::Base
   after_commit :flush_redis_cache
 
   def self.current
-    Rails.cache.fetch(CACHE_KEY) do
-      where('ends_at > :now AND starts_at <= :now', now: Time.zone.now)
-        .reorder(id: :asc)
-        .to_a
-    end
+    messages = Rails.cache.fetch(CACHE_KEY) { current_and_future_messages.to_a }
+
+    return messages if messages.empty?
+
+    now_or_future = messages.select(&:now_or_future?)
+
+    # If there are cached entries but none are to be displayed we'll purge the
+    # cache so we don't keep running this code all the time.
+    Rails.cache.delete(CACHE_KEY) if now_or_future.empty?
+
+    now_or_future.select(&:now?)
+  end
+
+  def self.current_and_future_messages
+    where('ends_at > :now', now: Time.zone.now).reorder(id: :asc)
   end
 
   def active?
@@ -38,6 +48,18 @@ class BroadcastMessage < ActiveRecord::Base
     ends_at < Time.zone.now
   end
 
+  def now?
+    (starts_at..ends_at).cover?(Time.zone.now)
+  end
+
+  def future?
+    starts_at > Time.zone.now
+  end
+
+  def now_or_future?
+    now? || future?
+  end
+
   def flush_redis_cache
     Rails.cache.delete(CACHE_KEY)
   end

changelogs/unreleased/fix-broadcast-message-caching.yml

+---
+title: Fix caching of future broadcast messages
+merge_request:
+author:
+type: fixed

spec/models/broadcast_message_spec.rb

@@ -53,6 +53,29 @@ describe BroadcastMessage do
 
       2.times { described_class.current }
     end
+
+    it 'includes messages that need to be displayed in the future' do
+      create(:broadcast_message)
+
+      future = create(
+        :broadcast_message,
+        starts_at: Time.now + 10.minutes,
+        ends_at: Time.now + 20.minutes
+      )
+
+      expect(described_class.current.length).to eq(1)
+
+      Timecop.travel(future.starts_at) do
+        expect(described_class.current.length).to eq(2)
+      end
+    end
+
+    it 'does not clear the cache if only a future message should be displayed' do
+      create(:broadcast_message, :future)
+
+      expect(Rails.cache).not_to receive(:delete)
+      expect(described_class.current.length).to eq(0)
+    end
   end
 
   describe '#active?' do