Introduce a new middleware for the test environment that can block requests

The idea is that after each feature spec example, we block all incoming
requests at the Rack level, go to the 'about:blank' page, and wait until
the current requests reach 0.

This should solve the problem where a request would end after database
cleaner performed the database truncation. The problem was that a GET
request can still lead to records creation (e.g. namespaces or routes).
Signed-off-by: NRémy Coutable <remy@rymai.me>

Gemfile

@@ -327,6 +327,7 @@ group :test do
   gem 'test_after_commit', '~> 1.1'
   gem 'sham_rack', '~> 1.3.6'
   gem 'timecop', '~> 0.8.0'
+  gem 'concurrent-ruby', '~> 1.0.5'
 end
 
 gem 'octokit', '~> 4.6.2'

Gemfile.lock

@@ -128,7 +128,7 @@ GEM
       execjs
     coffee-script-source (1.10.0)
     colorize (0.7.7)
-    concurrent-ruby (1.0.4)
+    concurrent-ruby (1.0.5)
     connection_pool (2.2.1)
     crack (0.4.3)
       safe_yaml (~> 1.0.0)
@@ -868,6 +868,7 @@ DEPENDENCIES
   chronic (~> 0.10.2)
   chronic_duration (~> 0.10.6)
   coffee-rails (~> 4.1.0)
+  concurrent-ruby (~> 1.0.5)
   connection_pool (~> 2.0)
   creole (~> 0.5.0)
   d3_rails (~> 3.5.0)

config/environments/test.rb

 Rails.application.configure do
+  # Make sure the middleware is inserted first in middleware chain
+  config.middleware.insert_before('ActionDispatch::Static', 'Gitlab::Testing::RequestBlockerMiddleware')
+
   # Settings specified here will take precedence over those in config/application.rb
 
   # The test environment is used exclusively to run your application's

lib/gitlab/testing/request_blocker_middleware.rb

+# 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

spec/spec_helper.rb

@@ -35,6 +35,7 @@ RSpec.configure do |config|
   config.include Warden::Test::Helpers, type: :request
   config.include LoginHelpers, type: :feature
   config.include SearchHelpers, type: :feature
+  config.include WaitForRequests, :js
   config.include WaitForAjax, type: :feature
   config.include StubConfiguration
   config.include EmailHelpers, type: :mailer

spec/support/wait_for_requests.rb

+module WaitForRequests
+  extend self
+
+  # This is inspired by http://www.salsify.com/blog/engineering/tearing-capybara-ajax-tests
+  def wait_for_requests_complete
+    stop_client
+    Gitlab::Testing::RequestBlockerMiddleware.block_requests!
+    wait_for('pending AJAX requests complete') do
+      Gitlab::Testing::RequestBlockerMiddleware.num_active_requests.zero?
+    end
+  ensure
+    Gitlab::Testing::RequestBlockerMiddleware.allow_requests!
+  end
+
+  # Navigate away from the current page which will prevent any new requests from being started
+  def stop_client
+    page.execute_script %Q{
+      window.location = "about:blank";
+    }
+  end
+
+  # Waits until the passed block returns true
+  def wait_for(condition_name, max_wait_time: Capybara.default_max_wait_time, polling_interval: 0.01)
+    wait_until = Time.now + max_wait_time.seconds
+    loop do
+      break if yield
+      if Time.now > wait_until
+        raise "Condition not met: #{condition_name}"
+      else
+        sleep(polling_interval)
+      end
+    end
+  end
+end
+
+RSpec.configure do |config|
+  config.after(:each, :js) do
+    wait_for_requests_complete
+  end
+end