Add exclusive lease to mergeability check processosw-avoid-errors-due-to-concurrent-calls

Concurrent calls to UserMergeToRef RPC updating a single ref
can lead to an opaque fail that is being rescued at Gitaly.

So this commit adds an exclusive lease to the mergeability
check process with the key as the current MR ID.

1 files changed, 13 insertions, 4 deletions

diff --git a/spec/lib/gitlab/exclusive_lease_helpers_spec.rb b/spec/lib/gitlab/exclusive_lease_helpers_spec.rb
index 5107e1efbbd..c3b706fc538 100644
--- a/spec/lib/gitlab/exclusive_lease_helpers_spec.rb
+++ b/spec/lib/gitlab/exclusive_lease_helpers_spec.rb
@@ -25,13 +25,13 @@ describe Gitlab::ExclusiveLeaseHelpers, :clean_gitlab_redis_shared_state do
       end
 
       it 'calls the given block' do
-        expect { |b| class_instance.in_lock(unique_key, &b) }.to yield_control.once
+        expect { |b| class_instance.in_lock(unique_key, &b) }.to yield_with_args(false)
       end
 
       it 'calls the given block continuously' do
-        expect { |b| class_instance.in_lock(unique_key, &b) }.to yield_control.once
-        expect { |b| class_instance.in_lock(unique_key, &b) }.to yield_control.once
-        expect { |b| class_instance.in_lock(unique_key, &b) }.to yield_control.once
+        expect { |b| class_instance.in_lock(unique_key, &b) }.to yield_with_args(false)
+        expect { |b| class_instance.in_lock(unique_key, &b) }.to yield_with_args(false)
+        expect { |b| class_instance.in_lock(unique_key, &b) }.to yield_with_args(false)
       end
 
       it 'cancels the exclusive lease after the block' do
@@ -68,6 +68,15 @@ describe Gitlab::ExclusiveLeaseHelpers, :clean_gitlab_redis_shared_state do
 
           expect { subject }.to raise_error('Failed to obtain a lock')
         end
+
+        context 'when lease is granted after retry' do
+          it 'yields block with true' do
+            expect(lease).to receive(:try_obtain).exactly(3).times { nil }
+            expect(lease).to receive(:try_obtain).once { unique_key }
+
+            expect { |b| class_instance.in_lock(unique_key, &b) }.to yield_with_args(true)
+          end
+        end
       end
 
       context 'when sleep second is specified' do