Handle query timeouts better

We currently get quite a few `ActiveRecord::QueryCancelled`
errors. This adds handling for this error in the following:

* The autocomplete web action
* All API actions

Changelog: changed

app/controllers/search_controller.rb

@@ -5,7 +5,7 @@ class SearchController < ApplicationController
   include SearchHelper
   include RedisTracking
 
-  RESCUE_FROM_TIMEOUT_ACTIONS = [:count, :show].freeze
+  RESCUE_FROM_TIMEOUT_ACTIONS = [:count, :show, :autocomplete].freeze
 
   track_redis_hll_event :show, name: 'i_search_total'
 
@@ -74,11 +74,7 @@ class SearchController < ApplicationController
   def autocomplete
     term = params[:term]
 
-    if params[:project_id].present?
-      @project = Project.find_by(id: params[:project_id])
-      @project = nil unless can?(current_user, :read_project, @project)
-    end
-
+    @project = search_service.project
     @ref = params[:project_ref] if params[:project_ref].present?
 
     render json: search_autocomplete_opts(term).to_json
@@ -189,17 +185,16 @@ class SearchController < ApplicationController
 
     @timeout = true
 
-    if count_action_name?
+    case action_name.to_sym
+    when :count
       render json: {}, status: :request_timeout
+    when :autocomplete
+      render json: [], status: :request_timeout
     else
       render status: :request_timeout
     end
   end
 
-  def count_action_name?
-    action_name.to_sym == :count
-  end
-
   def strip_surrounding_whitespace_from_search
     %i(term search).each { |param| params[param]&.strip! }
   end

lib/api/search.rb

@@ -8,6 +8,10 @@ module API
 
     feature_category :global_search
 
+    rescue_from ActiveRecord::QueryCanceled do |e|
+      render_api_error!({ error: 'Request timed out' }, 408)
+    end
+
     helpers do
       SCOPE_ENTITY = {
         merge_requests: Entities::MergeRequestBasic,

spec/controllers/search_controller_spec.rb

@@ -328,6 +328,7 @@ RSpec.describe SearchController do
     describe 'GET #autocomplete' do
       it_behaves_like 'when the user cannot read cross project', :autocomplete, { term: 'hello' }
       it_behaves_like 'with external authorization service enabled', :autocomplete, { term: 'hello' }
+      it_behaves_like 'support for active record query timeouts', :autocomplete, { term: 'hello' }, :project, :json
     end
 
     describe '#append_info_to_payload' do

spec/requests/api/search_spec.rb

@@ -122,6 +122,23 @@ RSpec.describe API::Search do
       end
     end
 
+    context 'when DB timeouts occur from global searches', :aggregate_errors do
+      %w(
+        issues
+        merge_requests
+        milestones
+        projects
+        snippet_titles
+        users
+      ).each do |scope|
+        it "returns a 408 error if search with scope: #{scope} times out" do
+          allow(SearchService).to receive(:new).and_raise ActiveRecord::QueryCanceled
+          get api(endpoint, user), params: { scope: scope, search: 'awesome' }
+          expect(response).to have_gitlab_http_status(:request_timeout)
+        end
+      end
+    end
+
     context 'when scope is not supported' do
       it 'returns 400 error' do
         get api(endpoint, user), params: { scope: 'unsupported', search: 'awesome' }