Introduce a new middleware for the test environment that can block requests28307-fix-sporadic-feature-spec-failures

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: Rémy Coutable <remy@rymai.me>

6 files changed, 108 insertions, 1 deletions

diff --git a/Gemfile b/Gemfile
index 2f813324a35..d9bdb0cd62e 100644
--- a/Gemfile
+++ b/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'
diff --git a/Gemfile.lock b/Gemfile.lock
index c60c045a4c2..a3861508d0f 100644
--- a/Gemfile.lock
+++ b/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)
diff --git a/config/environments/test.rb b/config/environments/test.rb
index fb25d3a8b14..a25c5016a3b 100644
--- a/config/environments/test.rb
+++ b/config/environments/test.rb
@@ -1,4 +1,7 @@
 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
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
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 5fda7c63cdb..409b97d6703 100644
--- a/spec/spec_helper.rb
+++ b/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
diff --git a/spec/support/wait_for_requests.rb b/spec/support/wait_for_requests.rb
new file mode 100644
index 00000000000..4a8958c7336
--- /dev/null
+++ b/spec/support/wait_for_requests.rb
@@ -0,0 +1,40 @@
+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