1 files changed, 63 insertions, 8 deletions

diff --git a/spec/services/issue_rebalancing_service_spec.rb b/spec/services/issue_rebalancing_service_spec.rb
index 7b3d4213b24..1c7f74264b7 100644
--- a/spec/services/issue_rebalancing_service_spec.rb
+++ b/spec/services/issue_rebalancing_service_spec.rb
@@ -3,31 +3,35 @@
 require 'spec_helper'
 
 RSpec.describe IssueRebalancingService do
-  let_it_be(:project) { create(:project) }
+  let_it_be(:project, reload: true) { create(:project) }
   let_it_be(:user) { project.creator }
   let_it_be(:start) { RelativePositioning::START_POSITION }
   let_it_be(:max_pos) { RelativePositioning::MAX_POSITION }
   let_it_be(:min_pos) { RelativePositioning::MIN_POSITION }
   let_it_be(:clump_size) { 300 }
 
-  let_it_be(:unclumped) do
-    (0..clump_size).to_a.map do |i|
+  let_it_be(:unclumped, reload: true) do
+    (1..clump_size).to_a.map do |i|
       create(:issue, project: project, author: user, relative_position: start + (1024 * i))
     end
   end
 
-  let_it_be(:end_clump) do
-    (0..clump_size).to_a.map do |i|
+  let_it_be(:end_clump, reload: true) do
+    (1..clump_size).to_a.map do |i|
       create(:issue, project: project, author: user, relative_position: max_pos - i)
     end
   end
 
-  let_it_be(:start_clump) do
-    (0..clump_size).to_a.map do |i|
+  let_it_be(:start_clump, reload: true) do
+    (1..clump_size).to_a.map do |i|
       create(:issue, project: project, author: user, relative_position: min_pos + i)
     end
   end
 
+  before do
+    stub_feature_flags(issue_rebalancing_with_retry: false)
+  end
+
   def issues_in_position_order
     project.reload.issues.reorder(relative_position: :asc).to_a
   end
@@ -101,19 +105,70 @@ RSpec.describe IssueRebalancingService do
     end
   end
 
+  shared_examples 'rebalancing is retried on statement timeout exceptions' do
+    subject { described_class.new(project.issues.first) }
+
+    it 'retries update statement' do
+      call_count = 0
+      allow(subject).to receive(:run_update_query) do
+        call_count += 1
+        if call_count < 13
+          raise(ActiveRecord::QueryCanceled)
+        else
+          call_count = 0 if call_count == 13 + 16 # 16 = 17 sub-batches - 1 call that succeeded as part of 5th batch
+          true
+        end
+      end
+
+      # call math:
+      # batches start at 100 and are split in half after every 3 retries if ActiveRecord::StatementTimeout exception is raised.
+      # We raise ActiveRecord::StatementTimeout exception for 13 calls:
+      # 1. 100 => 3 calls
+      # 2. 100/2=50 => 3 calls + 3 above = 6 calls, raise ActiveRecord::StatementTimeout
+      # 3. 50/2=25 => 3 calls + 6 above = 9 calls, raise ActiveRecord::StatementTimeout
+      # 4. 25/2=12 => 3 calls + 9 above = 12 calls, raise ActiveRecord::StatementTimeout
+      # 5. 12/2=6 => 1 call + 12 above = 13 calls, run successfully
+      #
+      # so out of 100 elements we created batches of 6 items => 100/6 = 17 sub-batches of 6 or less elements
+      #
+      # project.issues.count: 900 issues, so 9 batches of 100 => 9 * (13+16) = 261
+      expect(subject).to receive(:update_positions).exactly(261).times.and_call_original
+
+      subject.execute
+    end
+  end
+
   context 'when issue_rebalancing_optimization feature flag is on' do
     before do
       stub_feature_flags(issue_rebalancing_optimization: true)
     end
 
     it_behaves_like 'IssueRebalancingService shared examples'
+
+    context 'when issue_rebalancing_with_retry feature flag is on' do
+      before do
+        stub_feature_flags(issue_rebalancing_with_retry: true)
+      end
+
+      it_behaves_like 'IssueRebalancingService shared examples'
+      it_behaves_like 'rebalancing is retried on statement timeout exceptions'
+    end
   end
 
-  context 'when issue_rebalancing_optimization feature flag is on' do
+  context 'when issue_rebalancing_optimization feature flag is off' do
     before do
       stub_feature_flags(issue_rebalancing_optimization: false)
     end
 
     it_behaves_like 'IssueRebalancingService shared examples'
+
+    context 'when issue_rebalancing_with_retry feature flag is on' do
+      before do
+        stub_feature_flags(issue_rebalancing_with_retry: true)
+      end
+
+      it_behaves_like 'IssueRebalancingService shared examples'
+      it_behaves_like 'rebalancing is retried on statement timeout exceptions'
+    end
   end
 end