Catch and handle RateLimitedError exception

RateLimitedError is thrown when rate limit
throttling is being applied.

app/controllers/application_controller.rb

@@ -108,6 +108,12 @@ class ApplicationController < ActionController::Base
     head :forbidden, retry_after: Gitlab::Auth::UniqueIpsLimiter.config.unique_ips_limit_time_window
   end
 
+  rescue_from RateLimitedService::RateLimitedError do |e|
+    e.log_request(request, current_user)
+    response.headers.merge!(e.headers)
+    render plain: e.message, status: :too_many_requests
+  end
+
   def redirect_back_or_default(default: root_path, options: {})
     redirect_back(fallback_location: default, **options)
   end

lib/api/api.rb

@@ -124,6 +124,11 @@ module API
       handle_api_exception(exception)
     end
 
+    rescue_from RateLimitedService::RateLimitedError do |exception|
+      exception.log_request(context.request, context.current_user)
+      rack_response({ 'message' => { 'error' => exception.message } }.to_json, 429, exception.headers)
+    end
+
     format :json
     formatter :json, Gitlab::Json::GrapeFormatter
     content_type :json, 'application/json'

spec/controllers/projects/issues_controller_spec.rb

@@ -1411,6 +1411,7 @@ RSpec.describe Projects::IssuesController do
         stub_application_setting(issues_create_limit: 5)
       end
 
+      context 'when issue creation limits imposed' do
         it 'prevents from creating more issues', :request_store do
           5.times { post_new_issue }
 
@@ -1418,6 +1419,7 @@ RSpec.describe Projects::IssuesController do
             .to change { Gitlab::GitalyClient.get_request_count }.by(1) # creates 1 projects and 0 issues
 
           post_new_issue
+
           expect(response.body).to eq(_('This endpoint has been requested too many times. Try again later.'))
           expect(response).to have_gitlab_http_status(:too_many_requests)
         end
@@ -1447,6 +1449,7 @@ RSpec.describe Projects::IssuesController do
           end
         end
       end
+    end
 
     context 'setting issue type' do
       let(:issue_type) { 'issue' }

spec/graphql/mutations/issues/create_spec.rb

@@ -53,7 +53,11 @@ RSpec.describe Mutations::Issues::Create do
       stub_spam_services
     end
 
-    subject { mutation.resolve(**mutation_params) }
+    def resolve
+      mutation.resolve(**mutation_params)
+    end
+
+    subject { resolve }
 
     context 'when the user does not have permission to create an issue' do
       it 'raises an error' do
@@ -61,6 +65,15 @@ RSpec.describe Mutations::Issues::Create do
       end
     end
 
+    context 'when the user has exceeded the rate limit' do
+      it 'raises an error' do
+        allow(::Gitlab::ApplicationRateLimiter).to receive(:throttled?).and_return(true)
+        project.add_developer(user)
+
+        expect { resolve }.to raise_error(RateLimitedService::RateLimitedError, _('This endpoint has been requested too many times. Try again later.'))
+      end
+    end
+
     context 'when the user can create an issue' do
       context 'when creating an issue a developer' do
         before do

spec/lib/gitlab/email/handler/create_issue_handler_spec.rb

@@ -136,6 +136,36 @@ RSpec.describe Gitlab::Email::Handler::CreateIssueHandler do
         expect { handler.execute }.to raise_error(Gitlab::Email::ProjectNotFound)
       end
     end
+
+    context 'rate limiting' do
+      let(:rate_limited_service_feature_enabled) { nil }
+
+      before do
+        stub_feature_flags(rate_limited_service_issues_create: rate_limited_service_feature_enabled)
+      end
+
+      context 'when :rate_limited_service Feature is disabled' do
+        let(:rate_limited_service_feature_enabled) { false }
+
+        it 'does not attempt to throttle' do
+          expect(::Gitlab::ApplicationRateLimiter).not_to receive(:throttled?)
+
+          setup_attachment
+          receiver.execute
+        end
+      end
+
+      context 'when :rate_limited_service Feature is enabled' do
+        let(:rate_limited_service_feature_enabled) { true }
+
+        it 'raises a RateLimitedService::RateLimitedError' do
+          allow(::Gitlab::ApplicationRateLimiter).to receive(:throttled?).and_return(true)
+
+          setup_attachment
+          expect { receiver.execute }.to raise_error(RateLimitedService::RateLimitedError, _('This endpoint has been requested too many times. Try again later.'))
+        end
+      end
+    end
   end
 
   def email_fixture(path)

spec/lib/gitlab/email/handler/service_desk_handler_spec.rb

@@ -243,6 +243,15 @@ RSpec.describe Gitlab::Email::Handler::ServiceDeskHandler do
           end
         end
       end
+
+      context 'when rate limiting is in effect' do
+        it 'allows unlimited new issue creation' do
+          stub_application_setting(issues_create_limit: 1)
+          setup_attachment
+
+          expect { 2.times { receiver.execute } }.to change { Issue.count }.by(2)
+        end
+      end
     end
 
     describe '#can_handle?' do

spec/requests/api/issues/post_projects_issues_spec.rb

@@ -399,16 +399,15 @@ RSpec.describe API::Issues do
     end
 
     context 'when request exceeds the rate limit' do
-      before do
+      it 'prevents users from creating more issues' do
         allow(::Gitlab::ApplicationRateLimiter).to receive(:throttled?).and_return(true)
-      end
 
-      it 'prevents users from creating more issues' do
         post api("/projects/#{project.id}/issues", user),
         params: { title: 'new issue', labels: 'label, label2', weight: 3, assignee_ids: [user2.id] }
 
-        expect(response).to have_gitlab_http_status(:too_many_requests)
         expect(json_response['message']['error']).to eq('This endpoint has been requested too many times. Try again later.')
+
+        expect(response).to have_gitlab_http_status(:too_many_requests)
       end
     end
   end

spec/workers/email_receiver_worker_spec.rb

@@ -80,6 +80,21 @@ RSpec.describe EmailReceiverWorker, :mailer do
           expect(email).to be_nil
         end
       end
+
+      context 'when the error is RateLimitedService::RateLimitedError' do
+        let(:error) { RateLimitedService::RateLimitedError.new(key: :issues_create, rate_limiter: Gitlab::ApplicationRateLimiter) }
+
+        it 'does not report the error to the sender' do
+          expect(Gitlab::ErrorTracking).to receive(:track_exception).with(error).and_call_original
+
+          perform_enqueued_jobs do
+            described_class.new.perform(raw_message)
+          end
+
+          email = ActionMailer::Base.deliveries.last
+          expect(email).to be_nil
+        end
+      end
     end
   end