Use persistent Redis cluster for Workhorse pub/sub notifications

Previously, in Omnibus, Workhorse expected to listen via the Redis
shared state cluster for the `workhorse:notifications` publish/subscribe
channel, but the Rails code was using the Sidekiq queue cluster for
this. To fix this inconsistency, we make the Rails code use the
persistent cluster, since we don't want Workhorse to be looking at
anything Sidekiq-related.

app/models/ci/runner.rb

@@ -264,7 +264,7 @@ module Ci
     private
 
     def cleanup_runner_queue
-      Gitlab::Redis::Queues.with do |redis|
+      Gitlab::Redis::SharedState.with do |redis|
         redis.del(runner_queue_key)
       end
     end

changelogs/unreleased/sh-use-shared-state-cluster-pubsub.yml

@@ -0,0 +1,5 @@
+---
+title: Use persistent Redis cluster for Workhorse pub/sub notifications
+merge_request: 30990
+author:
+type: fixed

lib/gitlab/workhorse.rb

@@ -221,7 +221,7 @@ module Gitlab
       end
 
       def set_key_and_notify(key, value, expire: nil, overwrite: true)
-        Gitlab::Redis::Queues.with do |redis|
+        Gitlab::Redis::SharedState.with do |redis|
           result = redis.set(key, value, ex: expire, nx: !overwrite)
           if result
             redis.publish(NOTIFICATION_CHANNEL, "#{key}=#{value}")

spec/lib/gitlab/workhorse_spec.rb

@@ -404,6 +404,7 @@ describe Gitlab::Workhorse do
       end
 
       it 'set and notify' do
+        expect(Gitlab::Redis::SharedState).to receive(:with).and_call_original
         expect_any_instance_of(::Redis).to receive(:publish)
           .with(described_class::NOTIFICATION_CHANNEL, "test-key=test-value")
 

spec/models/ci/runner_spec.rb

@@ -554,7 +554,7 @@ describe Ci::Runner do
     end
 
     def expect_value_in_queues
-      Gitlab::Redis::Queues.with do |redis|
+      Gitlab::Redis::SharedState.with do |redis|
         runner_queue_key = runner.send(:runner_queue_key)
         expect(redis.get(runner_queue_key))
       end
@@ -627,7 +627,7 @@ describe Ci::Runner do
       end
 
       it 'cleans up the queue' do
-        Gitlab::Redis::Queues.with do |redis|
+        Gitlab::Redis::SharedState.with do |redis|
           expect(redis.get(queue_key)).to be_nil
         end
       end