Merge branch 'sh-fix-more-flaky-specs-16-3' into '16-3-stable-ee'

Fix flaky specs in 16-3-stable-ee

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/154623



Merged-by: Mayra Cabrera <mcabrera@gitlab.com>
Approved-by: Nao Hashizume <nhashizume@gitlab.com>
Approved-by: Mayra Cabrera <mcabrera@gitlab.com>
Co-authored-by: Lin Jen-Shin <jen-shin@gitlab.com>
Co-authored-by: Stan Hu <stanhu@gmail.com>

lib/gitlab/metrics/exporter/base_exporter.rb

@@ -68,11 +68,8 @@ def stop_working
           if server
             # we close sockets if thread is not longer running
             # this happens, when the process forks
-            if thread.alive?
-              server.shutdown
-            else
-              server.listeners.each(&:close)
-            end
+            server.listeners.each(&:close) unless thread.alive?
+            server.shutdown
           end
           @server = nil

spec/lib/gitlab/database/migration_helpers/restrict_gitlab_schema_spec.rb

@@ -3,7 +3,7 @@
 require 'spec_helper'
 RSpec.describe Gitlab::Database::MigrationHelpers::RestrictGitlabSchema, query_analyzers: false,
-  stub_feature_flags: false, feature_category: :cell do
+  stub_feature_flags: false, use_clean_rails_redis_caching: true, feature_category: :cell do
   let(:schema_class) { Class.new(Gitlab::Database::Migration[1.0]).include(described_class) }
   # We keep only the GitlabSchemasValidateConnection analyzer running

spec/lib/gitlab/metrics/exporter/base_exporter_spec.rb

@@ -216,7 +216,7 @@ def call(env)
       # in separate thread
       allow_any_instance_of(::WEBrick::HTTPServer)
         .to receive(:start).and_wrap_original do |m, *args|
-        Thread.new do
+        @server_thread = Thread.new do # rubocop:disable RSpec/InstanceVariable -- let does not work for this case
           m.call(*args)
         rescue IOError
           # is raised as we close listeners
@@ -224,8 +224,17 @@ def call(env)
       end
     end
+    attr_reader :server_thread
+
     after do
       exporter.stop
+
+      next unless server_thread
+
+      server_thread.join(0.05)
+      raise '`exporter.stop` should terminate `server_thread`' if server_thread.alive?
+    ensure
+      server_thread.kill.join if server_thread
     end
     with_them do

spec/support/helpers/stub_feature_flags.rb

@@ -22,6 +22,7 @@ def stub_all_feature_flags
   def unstub_all_feature_flags
     Feature.stub = false
+    Feature.reset_flipper
   end
   # Stub Feature flags with `flag_name: true/false`