Propagate broadcast messages to secondaries

app/models/broadcast_message.rb

 class BroadcastMessage < ActiveRecord::Base
+  prepend EE::BroadcastMessage
   include CacheMarkdownField
   include Sortable
 
@@ -19,7 +20,7 @@ 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 +37,10 @@ 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

doc/administration/geo/disaster_recovery/planned_failover.md

@@ -174,13 +174,6 @@ will take to finish syncing. An example message would be:
 > A scheduled maintenance will take place at XX:XX UTC. We expect it to take
   less than 1 hour.
 
-Until [issue #4930][ee-4930] is resolved, you may need to clear the Redis cache
-for the broadcast message to show. On the **secondary**, run:
-
-```
-sudo gitlab-rake cache:clear:redis
-```
-
 ## Prevent updates to the **primary**
 
 Until a [read-only mode][ce-19739] is implemented, updates must be prevented

ee/app/models/ee/broadcast_message.rb

+module EE
+  # BroadcastMessage EE mixin
+  #
+  # This module is intended to encapsulate EE-specific model logic
+  # and be prepended in the `BroadcastMessage` model
+  module BroadcastMessage
+    extend ActiveSupport::Concern
+
+    module ClassMethods
+      extend ::Gitlab::Utils::Override
+
+      override :cache_expires_in
+      def cache_expires_in
+        if ::Gitlab::Geo.secondary?
+          30.seconds
+        else
+          super
+        end
+      end
+    end
+  end
+end

ee/changelogs/unreleased/mk-geo-fix-broadcast-message-on-secondary.yml

+---
+title: 'Geo: Propagate broadcast messages to secondaries'
+merge_request: 5303
+author:
+type: fixed

ee/spec/models/broadcast_message_spec.rb

+require 'spec_helper'
+
+describe BroadcastMessage do
+  subject { build(:broadcast_message) }
+
+  describe '.current', :use_clean_rails_memory_store_caching do
+    context 'without Geo' do
+      it 'caches the output for a long time' do
+        expect(Gitlab::Geo).to receive(:enabled?).and_return(false).exactly(2).times
+
+        create(:broadcast_message)
+
+        expect(described_class).to receive(:where).and_call_original.once
+
+        described_class.current
+
+        Timecop.travel(1.year) do
+          described_class.current
+        end
+      end
+    end
+
+    context 'with Geo' do
+      context 'on the primary' do
+        it 'caches the output for a long time' do
+          expect(Gitlab::Geo).to receive(:secondary?).and_return(false).exactly(2).times
+
+          create(:broadcast_message)
+
+          expect(described_class).to receive(:where).and_call_original.once
+
+          described_class.current
+
+          Timecop.travel(1.year) do
+            described_class.current
+          end
+        end
+      end
+
+      context 'on a secondary' do
+        it 'caches the output for a short time' do
+          expect(Gitlab::Geo).to receive(:secondary?).and_return(true).exactly(3).times
+
+          create(:broadcast_message)
+
+          expect(described_class).to receive(:where).and_call_original.once
+
+          described_class.current
+
+          Timecop.travel(20.seconds) do
+            described_class.current
+          end
+
+          expect(described_class).to receive(:where).and_call_original.once
+
+          Timecop.travel(40.seconds) do
+            described_class.current
+          end
+        end
+      end
+    end
+  end
+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