Add correlation id in X-Request-ID for external pipeline validation

changelogs/unreleased/326106-correlation-id-to-validation-service.yml

+---
+title: Add correlation id in X-Request-ID for external pipeline validation
+merge_request: 58486
+author:
+type: other

lib/gitlab/ci/pipeline/chain/validate/external.rb

@@ -69,8 +69,10 @@ module Gitlab
             end
 
             def validate_service_request
-              headers = {}
-              headers['X-Gitlab-Token'] = validation_service_token if validation_service_token
+              headers = {
+                'X-Request-ID' => Labkit::Correlation::CorrelationId.current_id,
+                'X-Gitlab-Token' => validation_service_token
+              }.compact
 
               Gitlab::HTTP.post(
                 validation_service_url, timeout: validation_service_timeout,

spec/lib/gitlab/ci/pipeline/chain/validate/external_spec.rb

@@ -127,13 +127,23 @@ RSpec.describe Gitlab::Ci::Pipeline::Chain::Validate::External do
 
       it 'passes token in X-Gitlab-Token header' do
         expect(::Gitlab::HTTP).to receive(:post) do |_url, params|
-          expect(params[:headers]).to eq({ 'X-Gitlab-Token' => '123' })
+          expect(params[:headers]).to include({ 'X-Gitlab-Token' => '123' })
         end
 
         perform!
       end
     end
 
+    it 'passes the correlation id in X-Request-ID header' do
+      allow(Labkit::Correlation::CorrelationId).to receive(:current_id).and_return('correlation-id')
+
+      expect(::Gitlab::HTTP).to receive(:post) do |_url, params|
+        expect(params[:headers]).to include({ 'X-Request-ID' => 'correlation-id' })
+      end
+
+      perform!
+    end
+
     context 'when validation returns 200 OK' do
       before do
         stub_request(:post, validation_service_url).to_return(status: 200, body: "{}")