Respects Geo secondary node max capacity per shard

ee/app/workers/geo/secondary/repository_backfill_worker.rb

@@ -31,6 +31,7 @@ module Geo
 
               update_jobs_in_progress
 
+              unless over_capacity?
                 # This will stream the results one by one
                 # until there are no more results to fetch.
                 result = connection.get_result
@@ -40,8 +41,9 @@ module Geo
                 result.each do |row|
                   schedule_job(row['id'])
                 end
-
-              sleep(1) if over_capacity?
+              else
+                sleep(1)
+              end
             end
           rescue => error
             reason = :error
@@ -93,12 +95,15 @@ module Geo
       end
 
       def update_jobs_in_progress
-        status = Gitlab::SidekiqStatus.job_status(scheduled_job_ids)
+        job_ids = scheduled_job_ids
+        return if job_ids.empty?
 
         # SidekiqStatus returns an array of booleans: true if the job is still running, false otherwise.
         # For each entry, first use `zip` to make { job_id: 123 } -> [ { job_id: 123 }, bool ]
         # Next, filter out the jobs that have completed.
-        @scheduled_jobs = @scheduled_jobs.zip(status).map { |(job, running)| job if running }.compact
+        @scheduled_jobs = Gitlab::SidekiqStatus.job_status(scheduled_job_ids).then do |status|
+          @scheduled_jobs.zip(status).map { |(job, running)| job if running }.compact
+        end
       end
 
       def scheduled_job_ids

ee/spec/workers/geo/secondary/repository_backfill_worker_spec.rb

@@ -90,10 +90,14 @@ describe Geo::Secondary::RepositoryBackfillWorker, :geo, :geo_fdw, :clean_gitlab
 
     it 'respects Geo secondary node max capacity per shard' do
       stub_healthy_shards([shard_name, 'shard2', 'shard3', 'shard4', 'shard5'])
-      allow(Geo::ProjectSyncWorker).to receive(:perform_async).twice.and_return('jid-123')
-      create_list(:project, 2)
-
-      expect(subject).to receive(:sleep).twice.and_call_original
+      project_1 = create(:project)
+      project_2 = create(:project)
+      allow(Geo::ProjectSyncWorker).to receive(:perform_async).with(project_1.id, anything).and_return('jid-1')
+      allow(Geo::ProjectSyncWorker).to receive(:perform_async).with(project_2.id, anything).and_return('jid-2')
+      allow(Gitlab::SidekiqStatus).to receive(:job_status).with(['jid-2']).and_return([true], [false])
+      allow(Gitlab::SidekiqStatus).to receive(:job_status).with(['jid-1']).and_return([false])
+
+      expect(subject).to receive(:sleep).once.and_call_original
 
       subject.perform(shard_name)
     end