Don't try to deduplicate scheduled jobs

Sometimes we schedule jobs in the future. Now we'd mark them as
duplicates when scheduling them if there was already another job in
the queue with similar arguments.

But since the job could be for a long time in the future, no need to
mark it as a duplicate since it might be intentional to repeat the
work.

lib/gitlab/sidekiq_middleware/duplicate_jobs/client.rb

@@ -5,6 +5,9 @@ module Gitlab
     module DuplicateJobs
       class Client
         def call(worker_class, job, queue, _redis_pool, &block)
+          # We don't try to deduplicate jobs that are scheduled in the future
+          return yield if job['at']
+
           DuplicateJob.new(job, queue).schedule(&block)
         end
       end

spec/lib/gitlab/sidekiq_middleware/duplicate_jobs/client_spec.rb

@@ -30,5 +30,15 @@ describe Gitlab::SidekiqMiddleware::DuplicateJobs::Client, :clean_gitlab_redis_q
       expect(job2['duplicate-of']).to be_nil
       expect(job3['duplicate-of']).to eq(job1['jid'])
     end
+
+    it "does not mark a job that's scheduled in the future as a duplicate" do
+      TestDeduplicationWorker.perform_async('args1')
+      TestDeduplicationWorker.perform_at(1.day.from_now, 'args1')
+      TestDeduplicationWorker.perform_in(3.hours, 'args1')
+
+      duplicates = TestDeduplicationWorker.jobs.map { |job| job['duplicate-of'] }
+
+      expect(duplicates).to all(be_nil)
+    end
   end
 end