Merge branch 'add-correlation-id-to-500-page' into 'master'

Show request ID on 500 error page

See merge request gitlab-org/gitlab!77377

config/application.rb

@@ -68,6 +68,9 @@ module Gitlab
     require_dependency Rails.root.join('lib/gitlab/middleware/rack_multipart_tempfile_factory')
     require_dependency Rails.root.join('lib/gitlab/runtime')
     require_dependency Rails.root.join('lib/gitlab/patch/legacy_database_config')
+    require_dependency Rails.root.join('lib/gitlab/exceptions_app')
+
+    config.exceptions_app = Gitlab::ExceptionsApp.new(Rails.public_path)
 
     # To be removed in 15.0
     # This preload is needed to convert legacy `database.yml`

lib/gitlab/exceptions_app.rb

+# frozen_string_literal: true
+
+require_relative 'utils/override'
+
+module Gitlab
+  class ExceptionsApp < ActionDispatch::PublicExceptions
+    extend ::Gitlab::Utils::Override
+
+    REQUEST_ID_PLACEHOLDER = '<!-- REQUEST_ID -->'
+    REQUEST_ID_PARAGRAPH = '<p>Request ID: <code>%s</code></p>'
+
+    override :call
+    def call(env)
+      status, headers, body = super
+
+      if html_rendered? && body.first&.include?(REQUEST_ID_PLACEHOLDER)
+        body = [insert_request_id(env, body.first)]
+        headers['X-GitLab-Custom-Error'] = '1'
+      end
+
+      [status, headers, body]
+    end
+
+    private
+
+    override :render_html
+    def render_html(status)
+      @html_rendered = true
+
+      super
+    end
+
+    def html_rendered?
+      !!@html_rendered
+    end
+
+    def insert_request_id(env, body)
+      request_id = ERB::Util.html_escape(ActionDispatch::Request.new(env).request_id)
+
+      body.gsub(REQUEST_ID_PLACEHOLDER, REQUEST_ID_PARAGRAPH % [request_id])
+    end
+  end
+end

public/500.html

@@ -76,6 +76,7 @@
   <div class="container">
     <h3>Whoops, something went wrong on our end.</h3>
     <hr />
+    <!-- REQUEST_ID -->
     <p>Try refreshing the page, or going back and attempting the action again.</p>
     <p>Please contact your GitLab administrator if this problem persists.</p>
     <a href="javascript:history.back()" class="js-go-back go-back">Go back</a>

spec/lib/gitlab/exceptions_app_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Gitlab::ExceptionsApp, type: :request do
+  describe '.call' do
+    let(:exceptions_app) { described_class.new(Rails.public_path) }
+    let(:app) { ActionDispatch::ShowExceptions.new(error_raiser, exceptions_app) }
+
+    before do
+      @app = app
+    end
+
+    context 'for a 500 error' do
+      let(:error_raiser) { proc { raise 'an unhandled error' } }
+
+      context 'for an HTML request' do
+        it 'fills in the request ID' do
+          get '/', env: { 'action_dispatch.request_id' => 'foo' }
+
+          expect(response).to have_gitlab_http_status(:internal_server_error)
+          expect(response).to have_header('X-Gitlab-Custom-Error')
+          expect(response.body).to include('Request ID: <code>foo</code>')
+        end
+
+        it 'HTML-escapes the request ID' do
+          get '/', env: { 'action_dispatch.request_id' => '<b>foo</b>' }
+
+          expect(response).to have_gitlab_http_status(:internal_server_error)
+          expect(response).to have_header('X-Gitlab-Custom-Error')
+          expect(response.body).to include('Request ID: <code>&lt;b&gt;foo&lt;/b&gt;</code>')
+        end
+
+        it 'returns an empty 500 when the 500.html page cannot be found' do
+          allow(File).to receive(:exist?).and_return(false)
+
+          get '/', env: { 'action_dispatch.request_id' => 'foo' }
+
+          expect(response).to have_gitlab_http_status(:internal_server_error)
+          expect(response).not_to have_header('X-Gitlab-Custom-Error')
+          expect(response.body).to be_empty
+        end
+      end
+
+      context 'for a JSON request' do
+        it 'does not include the request ID' do
+          get '/', env: { 'action_dispatch.request_id' => 'foo' }, as: :json
+
+          expect(response).to have_gitlab_http_status(:internal_server_error)
+          expect(response).not_to have_header('X-Gitlab-Custom-Error')
+          expect(response.body).not_to include('foo')
+        end
+      end
+    end
+
+    context 'for a 404 error' do
+      let(:error_raiser) { proc { raise AbstractController::ActionNotFound } }
+
+      it 'returns a 404 response that does not include the request ID' do
+        get '/', env: { 'action_dispatch.request_id' => 'foo' }
+
+        expect(response).to have_gitlab_http_status(:not_found)
+        expect(response).not_to have_header('X-Gitlab-Custom-Error')
+        expect(response.body).not_to include('foo')
+      end
+    end
+  end
+end