Add redis db to the mail_room option hash

- change code to send the db option
- change mail_room configuration file

config/mail_room.yml

@@ -29,6 +29,7 @@
       :delivery_method: sidekiq
       :delivery_options:
         :redis_url: <%= config[:redis_url].to_json %>
+        :redis_db: <%= config[:redis_db] %>
         :namespace: <%= Gitlab::Redis::Queues::SIDEKIQ_NAMESPACE %>
         :queue: <%= config[:queue] %>
         :worker: <%= config[:worker] %>

lib/gitlab/mail_room.rb

@@ -71,7 +71,8 @@ module Gitlab
 
       def redis_config
         gitlab_redis_queues = Gitlab::Redis::Queues.new(rails_env)
-        config = { redis_url: gitlab_redis_queues.url }
+
+        config = { redis_url: gitlab_redis_queues.url, redis_db: gitlab_redis_queues.db }
 
         if gitlab_redis_queues.sentinels?
           config[:sentinels] = gitlab_redis_queues.sentinels

lib/gitlab/redis/wrapper.rb

@@ -96,6 +96,8 @@ module Gitlab
         end
 
         def instrumentation_class
+          return unless defined?(::Gitlab::Instrumentation::Redis)
+
           "::Gitlab::Instrumentation::Redis::#{store_name}".constantize
         end
       end
@@ -112,6 +114,10 @@ module Gitlab
         raw_config_hash[:url]
       end
 
+      def db
+        redis_store_options[:db]
+      end
+
       def sentinels
         raw_config_hash[:sentinels]
       end

spec/lib/gitlab/mail_room/mail_room_spec.rb

@@ -93,7 +93,7 @@ RSpec.describe Gitlab::MailRoom do
     end
 
     describe 'setting up redis settings' do
-      let(:fake_redis_queues) { double(url: "localhost", sentinels: "yes, them", sentinels?: true) }
+      let(:fake_redis_queues) { double(url: "localhost", db: 99, sentinels: "yes, them", sentinels?: true) }
 
       before do
         allow(Gitlab::Redis::Queues).to receive(:new).and_return(fake_redis_queues)
@@ -103,6 +103,7 @@ RSpec.describe Gitlab::MailRoom do
         config = described_class.enabled_configs.first
 
         expect(config[:redis_url]).to eq('localhost')
+        expect(config[:redis_db]).to eq(99)
         expect(config[:sentinels]).to eq('yes, them')
       end
     end

spec/lib/gitlab/redis/queues_spec.rb

@@ -9,10 +9,24 @@ RSpec.describe Gitlab::Redis::Queues do
   include_examples "redis_shared_examples"
 
   describe '#raw_config_hash' do
-    it 'has a legacy default URL' do
-      expect(subject).to receive(:fetch_config) { false }
+    before do
+      expect(subject).to receive(:fetch_config) { config }
+    end
+
+    context 'when the config url is blank' do
+      let(:config) { nil }
+
+      it 'has a legacy default URL' do
+        expect(subject.send(:raw_config_hash)).to eq(url: 'redis://localhost:6381' )
+      end
+    end
+
+    context 'when the config url is present' do
+      let(:config) { { url: 'redis://localhost:1111' } }
 
-      expect(subject.send(:raw_config_hash)).to eq(url: 'redis://localhost:6381' )
+      it 'sets the configured url' do
+        expect(subject.send(:raw_config_hash)).to eq(url: 'redis://localhost:1111' )
+      end
     end
   end
 end

spec/support/redis/redis_shared_examples.rb

@@ -255,6 +255,28 @@ RSpec.shared_examples "redis_shared_examples" do
     end
   end
 
+  describe '#db' do
+    let(:rails_env) { 'development' }
+
+    subject { described_class.new(rails_env).db }
+
+    context 'with old format' do
+      let(:config_file_name) { config_old_format_host }
+
+      it 'returns the correct db' do
+        expect(subject).to eq(redis_database)
+      end
+    end
+
+    context 'with new format' do
+      let(:config_file_name) { config_new_format_host }
+
+      it 'returns the correct db' do
+        expect(subject).to eq(redis_database)
+      end
+    end
+  end
+
   describe '#sentinels' do
     subject { described_class.new(rails_env).sentinels }