Fix ElasticCommitIndexerWorker FK violation

ee/changelogs/unreleased/240923-fix-foreign-key-violation.yml

+---
+title: Fix unnecessary Sidekiq errors/retries when project is deleted during indexing
+merge_request: 45249
+author:
+type: fixed

ee/lib/gitlab/elastic/indexer.rb

@@ -177,6 +177,15 @@ module Gitlab
 
       # rubocop: disable CodeReuse/ActiveRecord
       def update_index_status(to_sha)
+        unless Project.exists?(id: project.id)
+          Gitlab::Elasticsearch::Logger.build.debug(
+            message: 'Index status could not be updated as the project does not exist',
+            project_id: project.id,
+            wiki: index_wiki?
+          )
+          return false
+        end
+
         raise "Invalid sha #{to_sha}" unless to_sha.present?
 
         # An index_status should always be created,

ee/spec/lib/gitlab/elastic/indexer_spec.rb

@@ -388,6 +388,25 @@ RSpec.describe Gitlab::Elastic::Indexer do
     end
   end
 
+  context 'when project no longer exists in database' do
+    let!(:logger_double) { instance_double(Gitlab::Elasticsearch::Logger) }
+
+    before do
+      allow(Gitlab::Elasticsearch::Logger).to receive(:build).and_return(logger_double)
+      allow(indexer).to receive(:run_indexer!) { Project.where(id: project.id).delete_all }
+    end
+
+    it 'does not raises an exception and prints log message' do
+      expect(logger_double).to receive(:debug).with(
+        message: 'Index status could not be updated as the project does not exist',
+        project_id: project.id,
+        wiki: false
+      )
+      expect(IndexStatus).not_to receive(:safe_find_or_create_by!).with(project_id: project.id)
+      expect { indexer.run }.not_to raise_error
+    end
+  end
+
   def expect_popen
     expect(Gitlab::Popen).to receive(:popen)
   end