1 files changed, 61 insertions, 0 deletions
diff --git a/lib/gitlab/testing/request_blocker_middleware.rb b/lib/gitlab/testing/request_blocker_middleware.rb
new file mode 100644
index 00000000000..aa67fa08577
--- /dev/null
+++ b/lib/gitlab/testing/request_blocker_middleware.rb
@@ -0,0 +1,61 @@
+# rubocop:disable Style/ClassVars
+
+# This is inspired by http://www.salsify.com/blog/engineering/tearing-capybara-ajax-tests
+# Rack middleware that keeps track of the number of active requests and can block new requests.
+module Gitlab
+  module Testing
+    class RequestBlockerMiddleware
+      @@num_active_requests = Concurrent::AtomicFixnum.new(0)
+      @@block_requests = Concurrent::AtomicBoolean.new(false)
+
+      # Returns the number of requests the server is currently processing.
+      def self.num_active_requests
+        @@num_active_requests.value
+      end
+
+      # Prevents the server from accepting new requests. Any new requests will return an HTTP
+      # 503 status.
+      def self.block_requests!
+        @@block_requests.value = true
+      end
+
+      # Allows the server to accept requests again.
+      def self.allow_requests!
+        @@block_requests.value = false
+      end
+
+      def initialize(app)
+        @app = app
+      end
+
+      def call(env)
+        increment_active_requests
+        if block_requests?
+          block_request(env)
+        else
+          @app.call(env)
+        end
+      ensure
+        decrement_active_requests
+      end
+
+      private
+
+      def block_requests?
+        @@block_requests.true?
+      end
+
+      def block_request(env)
+        [503, {}, []]
+      end
+
+      def increment_active_requests
+        @@num_active_requests.increment
+      end
+
+      def decrement_active_requests
+        @@num_active_requests.decrement
+      end
+    end
+  end
+end