Fix reloading in dev with user-level fibers

Author: rsamoilov

lib/rage/middleware/reloader.rb

@@ -5,7 +5,9 @@ def initialize(app)
     Iodine.on_state(:on_start) do
       Rage.code_loader.check_updated!
     end
+
     @app = app
+    @mutex = Mutex.new
   end
 
   def call(env)
@@ -21,13 +23,10 @@ def call(env)
   private
 
   def with_reload
-    if Rage.code_loader.check_updated!
-      Fiber.new(blocking: true) {
-        Rage.code_loader.reload
-        yield
-      }.resume
-    else
-      yield
+    @mutex.synchronize do
+      Rage.code_loader.reload if Rage.code_loader.check_updated!
     end
+
+    yield
   end
 end

spec/integration/integration_spec.rb

@@ -274,4 +274,79 @@
       expect(response.code).to eq(200)
     end
   end
+
+  context "with reload" do
+    let(:controller) { Pathname.new("#{__dir__}/test_app/app/controllers/reload_controller.rb") }
+
+    before do
+      @initial = controller.read
+    end
+
+    after do
+      controller.write(@initial)
+    end
+
+    context "with new status" do
+      before do
+        controller.write <<~RUBY
+          class ReloadController < RageController::API
+            def verify
+              head 207
+            end
+          end
+        RUBY
+      end
+
+      it "reloads the app" do
+        response = HTTP.get("http://localhost:3000/reload/verify")
+        expect(response.code).to eq(207)
+      end
+    end
+
+    context "with async code" do
+      before do
+        controller.write <<~RUBY
+          class ReloadController < RageController::API
+            def verify
+              f1 = Fiber.schedule { sleep 0.1 }
+              f2 = Fiber.schedule { sleep 0.2 }
+              Fiber.await([f1, f2])
+
+              head 205
+            end
+          end
+        RUBY
+      end
+
+      it "reloads the app" do
+        response = HTTP.get("http://localhost:3000/reload/verify")
+        expect(response.code).to eq(205)
+      end
+    end
+
+    context "with parallel requests" do
+      before do
+        controller.write <<~RUBY
+          class ReloadController < RageController::API
+            def verify
+              sleep 0.1
+              head 208
+            end
+          end
+        RUBY
+      end
+
+      it "reloads the app" do
+        requests = [
+          Thread.new { HTTP.get("http://localhost:3000/reload/verify") },
+          Thread.new { HTTP.get("http://localhost:3000/reload/verify") }
+        ]
+
+        requests.each(&:join)
+        responses = requests.map(&:value)
+
+        expect(responses.map(&:code).uniq).to eq([208])
+      end
+    end
+  end
 end

spec/integration/test_app/app/controllers/reload_controller.rb

@@ -0,0 +1,4 @@
+class ReloadController < RageController::API
+  def verify
+  end
+end

spec/integration/test_app/config/environments/development.rb

@@ -8,4 +8,6 @@
   # Specify the logger
   config.logger = Rage::Logger.new("log/development.log")
   config.log_level = Logger::INFO
+
+  config.middleware.use Rage::Reloader
 end

spec/integration/test_app/config/routes.rb

@@ -26,6 +26,8 @@
   get "logs/custom", to: "logs#custom"
   get "logs/fiber", to: "logs#fiber"
 
+  get "reload/verify", to: "reload#verify"
+
   mount ->(_) { [200, {}, ""] }, at: "/admin"
 
   namespace :api do