Use at_exit hook to shut down periodic_updater

* avoids use of sleep commands

Author: jochenehret

lib/cloud_controller/runners/puma_runner.rb

@@ -62,7 +62,10 @@ def initialize(config, app, logger, periodic_updater, request_logs)
         prometheus_updater.update_gauge_metric(:cc_db_connection_pool_timeouts_total, 0, labels: { process_type: 'main' })
         @periodic_updater.setup_updates
       end
-      events.after_stopped(&method(:shutdown_periodic_updater))
+
+      events.after_stopped do
+        stop_periodic_updates
+      end
 
       @puma_launcher = Puma::Launcher.new(puma_config, log_writer:, events:)
     end
@@ -76,19 +79,16 @@ def start!
 
     private
 
-    def shutdown_periodic_updater
-      if @periodic_updater
-        Thread.new do
-          # Give the trap handler a moment to return before taking any locks.
-          sleep 0.05
-          @periodic_updater.stop_updates
-        rescue StandardError => e
-          @logger.error "Failed to stop periodic updates cleanly: #{e}\n#{e.backtrace&.join("\n")}"
-        end
+    def stop_periodic_updates
+      @periodic_updater&.stop_updates
+      @logger.info('Successfully stopped periodic updates in after_stopped')
+    rescue ThreadError
+      at_exit do
+        @periodic_updater&.stop_updates
+        @logger.info('Successfully stopped periodic updates in at_exit')
       end
     rescue StandardError => e
-      # Never let exceptions from the trap context bubble up and crash shutdown.
-      @logger.error "Failed to schedule periodic updates shutdown: #{e}\n#{e.backtrace&.join("\n")}"
+      @logger.error("Failed to stop periodic updates: #{e}\n#{e.backtrace&.join("\n")}")
     end
 
     def prometheus_updater

spec/unit/lib/cloud_controller/runners/puma_runner_spec.rb

@@ -208,7 +208,6 @@ module VCAP::CloudController
           expect(periodic_updater).to receive(:stop_updates)
 
           puma_launcher.events.fire(:after_stopped)
-          sleep 0.1
         end
       end
     end