Merge branch 'sh-optimize-read-only-check' into 'master'

Optimize read-only middleware so that it does not consume as much CPU

Closes #40185 and gitlab-com/infrastructure#3240

See merge request gitlab-org/gitlab-ce!15504

lib/gitlab/middleware/read_only.rb

@@ -58,7 +58,7 @@ module Gitlab
       end
 
       def last_visited_url
-        @env['HTTP_REFERER'] || rack_session['user_return_to'] || Rails.application.routes.url_helpers.root_url
+        @env['HTTP_REFERER'] || rack_session['user_return_to'] || Gitlab::Routing.url_helpers.root_url
       end
 
       def route_hash
@@ -74,10 +74,16 @@ module Gitlab
       end
 
       def grack_route
+        # Calling route_hash may be expensive. Only do it if we think there's a possible match
+        return false unless request.path.end_with?('.git/git-upload-pack')
+
         route_hash[:controller] == 'projects/git_http' && route_hash[:action] == 'git_upload_pack'
       end
 
       def lfs_route
+        # Calling route_hash may be expensive. Only do it if we think there's a possible match
+        return false unless request.path.end_with?('/info/lfs/objects/batch')
+
         route_hash[:controller] == 'projects/lfs_api' && route_hash[:action] == 'batch'
       end
     end

spec/lib/gitlab/middleware/read_only_spec.rb

@@ -84,14 +84,23 @@ describe Gitlab::Middleware::ReadOnly do
     end
 
     it 'expects POST of new file that looks like an LFS batch url to be disallowed' do
+      expect(Rails.application.routes).to receive(:recognize_path).and_call_original
       response = request.post('/root/gitlab-ce/new/master/app/info/lfs/objects/batch')
 
       expect(response).to be_a_redirect
       expect(subject).to disallow_request
     end
 
+    it 'returns last_vistited_url for disallowed request' do
+      response = request.post('/test_request')
+
+      expect(response.location).to eq 'http://localhost/'
+    end
+
     context 'whitelisted requests' do
       it 'expects a POST internal request to be allowed' do
+        expect(Rails.application.routes).not_to receive(:recognize_path)
+
         response = request.post("/api/#{API::API.version}/internal")
 
         expect(response).not_to be_a_redirect
@@ -99,6 +108,7 @@ describe Gitlab::Middleware::ReadOnly do
       end
 
       it 'expects a POST LFS request to batch URL to be allowed' do
+        expect(Rails.application.routes).to receive(:recognize_path).and_call_original
         response = request.post('/root/rouge.git/info/lfs/objects/batch')
 
         expect(response).not_to be_a_redirect
@@ -106,6 +116,7 @@ describe Gitlab::Middleware::ReadOnly do
       end
 
       it 'expects a POST request to git-upload-pack URL to be allowed' do
+        expect(Rails.application.routes).to receive(:recognize_path).and_call_original
         response = request.post('/root/rouge.git/git-upload-pack')
 
         expect(response).not_to be_a_redirect