1 files changed, 63 insertions, 0 deletions
diff --git a/rubocop/cop/worker_data_consistency.rb b/rubocop/cop/worker_data_consistency.rb
new file mode 100644
index 00000000000..e9047750f3e
--- /dev/null
+++ b/rubocop/cop/worker_data_consistency.rb
@@ -0,0 +1,63 @@
+# frozen_string_literal: true
+
+require_relative '../code_reuse_helpers'
+
+module RuboCop
+  module Cop
+    # This cop checks for a call to `data_consistency` to exist in Sidekiq workers.
+    #
+    # @example
+    #
+    # # bad
+    # class BadWorker
+    #   def perform
+    #   end
+    # end
+    #
+    # # good
+    # class GoodWorker
+    #   data_consistency :delayed
+    #
+    #   def perform
+    #   end
+    # end
+    #
+    class WorkerDataConsistency < RuboCop::Cop::Cop
+      include CodeReuseHelpers
+
+      HELP_LINK = 'https://docs.gitlab.com/ee/development/sidekiq_style_guide.html#job-data-consistency-strategies'
+
+      MSG = <<~MSG
+        Should define data_consistency expectation.
+
+        It is encouraged for workers to use database replicas as much as possible by declaring
+        data_consistency to use the :delayed or :sticky modes. Mode :always will result in the
+        worker always hitting the primary database node for both reads and writes, which limits
+        scalability.
+
+        Some guidelines:
+        
+        1. If your worker mostly writes or reads its own writes, use mode :always. TRY TO AVOID THIS.
+        2. If your worker performs mostly reads and can tolerate small delays, use mode :delayed.
+        3. If your worker performs mostly reads but cannot tolerate any delays, use mode :sticky.
+
+        See #{HELP_LINK} for a more detailed explanation of these settings.
+      MSG
+
+      def_node_search :application_worker?, <<~PATTERN
+      `(send nil? :include (const nil? :ApplicationWorker))
+      PATTERN
+
+      def_node_search :data_consistency_defined?, <<~PATTERN
+        `(send nil? :data_consistency ...)
+      PATTERN
+
+      def on_class(node)
+        return unless in_worker?(node) && application_worker?(node)
+        return if data_consistency_defined?(node)
+
+        add_offense(node, location: :expression)
+      end
+    end
+  end
+end