Remove implicit job deduplication feature flags

We added these as a safety net, but:

1. We've never used them.
2. There's an implicit feature flag per idempotent worker.
3. Idempotency and job deduplication are now well established in our
   codebase.

So we don't need them any more.

doc/development/sidekiq_style_guide.md

@@ -251,26 +251,6 @@ module AuthorizedProjectUpdate
 end
 ```
 
-#### Troubleshooting
-
-If the automatic deduplication were to cause issues in certain
-queues. This can be temporarily disabled by enabling a feature flag
-named `disable_<queue name>_deduplication`. For example to disable
-deduplication for the `AuthorizedProjectsWorker`, we would enable the
-feature flag `disable_authorized_projects_deduplication`.
-
-From ChatOps:
-
-```shell
-/chatops run feature set disable_authorized_projects_deduplication true
-```
-
-From the rails console:
-
-```ruby
-Feature.enable!(:disable_authorized_projects_deduplication)
-```
-
 ## Limited capacity worker
 
 It is possible to limit the number of concurrent running jobs for a worker class

lib/gitlab/sidekiq_middleware/duplicate_jobs/duplicate_job.rb

@@ -70,10 +70,6 @@ module Gitlab
           jid != existing_jid
         end
 
-        def droppable?
-          idempotent? && ::Feature.disabled?("disable_#{queue_name}_deduplication", type: :ops)
-        end
-
         def scheduled_at
           job['at']
         end
@@ -85,6 +81,13 @@ module Gitlab
           worker_klass.get_deduplication_options
         end
 
+        def idempotent?
+          return false unless worker_klass
+          return false unless worker_klass.respond_to?(:idempotent?)
+
+          worker_klass.idempotent?
+        end
+
         private
 
         attr_reader :queue_name, :job
@@ -128,13 +131,6 @@ module Gitlab
         def idempotency_string
           "#{worker_class_name}:#{arguments.join('-')}"
         end
-
-        def idempotent?
-          return false unless worker_klass
-          return false unless worker_klass.respond_to?(:idempotent?)
-
-          worker_klass.idempotent?
-        end
       end
     end
   end

lib/gitlab/sidekiq_middleware/duplicate_jobs/strategies/deduplicates_when_scheduling.rb

@@ -13,7 +13,7 @@ module Gitlab
             if deduplicatable_job? && check! && duplicate_job.duplicate?
               job['duplicate-of'] = duplicate_job.existing_jid
 
-              if duplicate_job.droppable?
+              if duplicate_job.idempotent?
                 Gitlab::SidekiqLogging::DeduplicationLogger.instance.log(
                   job, "dropped #{strategy_name}", duplicate_job.options)
                 return false

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

@@ -131,31 +131,6 @@ RSpec.describe Gitlab::SidekiqMiddleware::DuplicateJobs::DuplicateJob, :clean_gi
     end
   end
 
-  describe '#droppable?' do
-    where(:idempotent, :prevent_deduplication) do
-      # [true, false].repeated_permutation(2)
-      [[true, true],
-       [true, false],
-       [false, true],
-       [false, false]]
-    end
-
-    with_them do
-      before do
-        allow(AuthorizedProjectsWorker).to receive(:idempotent?).and_return(idempotent)
-        stub_feature_flags("disable_#{queue}_deduplication" => prevent_deduplication)
-      end
-
-      it 'is droppable when all conditions are met' do
-        if idempotent && !prevent_deduplication
-          expect(duplicate_job).to be_droppable
-        else
-          expect(duplicate_job).not_to be_droppable
-        end
-      end
-    end
-  end
-
   describe '#scheduled_at' do
     let(:scheduled_at) { 42 }
     let(:job) do
@@ -181,6 +156,46 @@ RSpec.describe Gitlab::SidekiqMiddleware::DuplicateJobs::DuplicateJob, :clean_gi
     end
   end
 
+  describe '#idempotent?' do
+    context 'when worker class does not exist' do
+      let(:job) { { 'class' => '' } }
+
+      it 'returns false' do
+        expect(duplicate_job).not_to be_idempotent
+      end
+    end
+
+    context 'when worker class does not respond to #idempotent?' do
+      before do
+        stub_const('AuthorizedProjectsWorker', Class.new)
+      end
+
+      it 'returns false' do
+        expect(duplicate_job).not_to be_idempotent
+      end
+    end
+
+    context 'when worker class is not idempotent' do
+      before do
+        allow(AuthorizedProjectsWorker).to receive(:idempotent?).and_return(false)
+      end
+
+      it 'returns false' do
+        expect(duplicate_job).not_to be_idempotent
+      end
+    end
+
+    context 'when worker class is idempotent' do
+      before do
+        allow(AuthorizedProjectsWorker).to receive(:idempotent?).and_return(true)
+      end
+
+      it 'returns true' do
+        expect(duplicate_job).to be_idempotent
+      end
+    end
+  end
+
   def set_idempotency_key(key, value = '1')
     Sidekiq.redis { |r| r.set(key, value) }
   end

spec/support/shared_examples/lib/gitlab/sidekiq_middleware/strategy_shared_examples.rb

@@ -38,7 +38,7 @@ RSpec.shared_examples 'deduplicating jobs when scheduling' do |strategy_name|
       it 'adds the jid of the existing job to the job hash' do
         allow(fake_duplicate_job).to receive(:scheduled?).and_return(false)
         allow(fake_duplicate_job).to receive(:check!).and_return('the jid')
-        allow(fake_duplicate_job).to receive(:droppable?).and_return(true)
+        allow(fake_duplicate_job).to receive(:idempotent?).and_return(true)
         allow(fake_duplicate_job).to receive(:options).and_return({})
         job_hash = {}
 
@@ -62,7 +62,7 @@ RSpec.shared_examples 'deduplicating jobs when scheduling' do |strategy_name|
               receive(:check!)
                 .with(Gitlab::SidekiqMiddleware::DuplicateJobs::DuplicateJob::DUPLICATE_KEY_TTL)
                 .and_return('the jid'))
-            allow(fake_duplicate_job).to receive(:droppable?).and_return(true)
+            allow(fake_duplicate_job).to receive(:idempotent?).and_return(true)
             job_hash = {}
 
             expect(fake_duplicate_job).to receive(:duplicate?).and_return(true)
@@ -82,7 +82,7 @@ RSpec.shared_examples 'deduplicating jobs when scheduling' do |strategy_name|
               allow(fake_duplicate_job).to receive(:options).and_return({ including_scheduled: true })
               allow(fake_duplicate_job).to(
                 receive(:check!).with(time_diff.to_i).and_return('the jid'))
-              allow(fake_duplicate_job).to receive(:droppable?).and_return(true)
+              allow(fake_duplicate_job).to receive(:idempotent?).and_return(true)
               job_hash = {}
 
               expect(fake_duplicate_job).to receive(:duplicate?).and_return(true)
@@ -104,13 +104,13 @@ RSpec.shared_examples 'deduplicating jobs when scheduling' do |strategy_name|
         allow(fake_duplicate_job).to receive(:duplicate?).and_return(true)
         allow(fake_duplicate_job).to receive(:options).and_return({})
         allow(fake_duplicate_job).to receive(:existing_jid).and_return('the jid')
-        allow(fake_duplicate_job).to receive(:droppable?).and_return(true)
+        allow(fake_duplicate_job).to receive(:idempotent?).and_return(true)
       end
 
       it 'drops the job' do
         schedule_result = nil
 
-        expect(fake_duplicate_job).to receive(:droppable?).and_return(true)
+        expect(fake_duplicate_job).to receive(:idempotent?).and_return(true)
 
         expect { |b| schedule_result = strategy.schedule({}, &b) }.not_to yield_control
         expect(schedule_result).to be(false)