Backport: Propagate broadcast messages to secondaries

app/models/broadcast_message.rb

@@ -19,7 +19,7 @@ class BroadcastMessage < ActiveRecord::Base
   after_commit :flush_redis_cache
 
   def self.current
-    messages = Rails.cache.fetch(CACHE_KEY) { current_and_future_messages.to_a }
+    messages = Rails.cache.fetch(CACHE_KEY, expires_in: cache_expires_in) { current_and_future_messages.to_a }
 
     return messages if messages.empty?
 
@@ -36,6 +36,10 @@ class BroadcastMessage < ActiveRecord::Base
     where('ends_at > :now', now: Time.zone.now).order_id_asc
   end
 
+  def self.cache_expires_in
+    nil
+  end
+
   def active?
     started? && !ended?
   end

spec/models/broadcast_message_spec.rb

@@ -51,7 +51,11 @@ describe BroadcastMessage do
 
       expect(described_class).to receive(:where).and_call_original.once
 
-      2.times { described_class.current }
+      described_class.current
+
+      Timecop.travel(1.year) do
+        described_class.current
+      end
     end
 
     it 'includes messages that need to be displayed in the future' do