Update each backorder only once in bulk cancel

app/jobs/amend_backorder_job.rb

@@ -5,6 +5,15 @@
 class AmendBackorderJob < ApplicationJob
   sidekiq_options retry: 0
 
+  def self.schedule_bulk_update_for(orders)
+    # We can have one backorder per order cycle and distributor.
+    groups = orders.group_by { |order| [order.order_cycle, order.distributor] }
+    groups.each_value do |orders_with_same_backorder|
+      # We need to trigger only one update per backorder.
+      perform_later(orders_with_same_backorder.first)
+    end
+  end
+
   def perform(order)
     OrderLocker.lock_order_and_variants(order) do
       amend_backorder(order)

app/services/orders/bulk_cancel_service.rb

@@ -15,8 +15,7 @@ module Orders
         order.send_cancellation_email = @send_cancellation_email
         order.restock_items = @restock_items
         order.cancel
-        AmendBackorderJob.perform_later(order)
-      end
+      end.tap { |orders| AmendBackorderJob.schedule_bulk_update_for(orders) }
       # rubocop:enable Rails/FindEach
     end
 

spec/jobs/amend_backorder_job_spec.rb

@@ -50,6 +50,29 @@ RSpec.describe AmendBackorderJob do
     chia_seed.on_hand = 7
   end
 
+  describe ".schedule_bulk_update_for" do
+    let(:order_same_oc) {
+      create(
+        :completed_order_with_totals,
+        distributor: order.distributor,
+        order_cycle: order.order_cycle,
+      )
+    }
+    let(:order_other_oc) { create(:completed_order_with_totals) }
+
+    it "enqueues only one job per backorder" do
+      expect {
+        AmendBackorderJob.schedule_bulk_update_for([order, order_same_oc])
+      }.to enqueue_job(AmendBackorderJob).exactly(:once)
+    end
+
+    it "enqueues a job for each backorder" do
+      expect {
+        AmendBackorderJob.schedule_bulk_update_for([order, order_other_oc])
+      }.to enqueue_job(AmendBackorderJob).exactly(:twice)
+    end
+  end
+
   describe "#amend_backorder" do
     it "updates an order" do
       stub_request(:get, catalog_url).to_return(body: catalog_json)