Support backward compatibility when introduce new failure reason

app/models/commit_status.rb

@@ -109,7 +109,7 @@ class CommitStatus < ActiveRecord::Base
 
     before_transition any => :failed do |commit_status, transition|
       failure_reason = transition.args.first
-      commit_status.failure_reason = failure_reason
+      commit_status.failure_reason = CommitStatus.failure_reasons[failure_reason]
     end
 
     after_transition do |commit_status, transition|

changelogs/unreleased/avoid-lock-when-introduce-new-failure-reason.yml

+---
+title: Support backward compatibility when introduce new failure reason
+merge_request: 22566
+author:
+type: changed

lib/api/runner.rb

@@ -142,8 +142,7 @@ module API
         requires :id, type: Integer, desc: %q(Job's ID)
         optional :trace, type: String, desc: %q(Job's full trace)
         optional :state, type: String, desc: %q(Job's status: success, failed)
-        optional :failure_reason, type: String, values: CommitStatus.failure_reasons.keys,
-                                  desc: %q(Job's failure_reason)
+        optional :failure_reason, type: String, desc: %q(Job's failure_reason)
       end
       put '/:id' do
         job = authenticate_job!

spec/requests/api/runner_spec.rb

@@ -797,6 +797,15 @@ describe API::Runner, :clean_gitlab_redis_shared_state do
 
           it { expect(job).to be_runner_system_failure }
         end
+
+        context 'when failure_reason is unrecognized value' do
+          before do
+            update_job(state: 'failed', failure_reason: 'what_is_this')
+            job.reload
+          end
+
+          it { expect(job).to be_unknown_failure }
+        end
       end
 
       context 'when trace is given' do