Prevent interweaving apps flushing

Change-Id: Ic6dbc7c23dde78e855bc7701a3b384379e99bb70

lib/router/router.rb

@@ -40,6 +40,7 @@ def config(config)
         @flush_apps_interval = config['flush_apps_interval'] || 30
         @active_apps = Set.new
         @flushing_apps = Set.new
+        @flushing = false
       end
     end
 
@@ -235,6 +236,9 @@ def add_active_app(app_id)
     def flush_active_apps
       return unless @enable_nonprod_apps
 
+      return if @flushing
+      @flushing = true
+
       @active_apps, @flushing_apps = @flushing_apps, @active_apps
       @active_apps.clear
 
@@ -244,6 +248,8 @@ def flush_active_apps
 
         log.info("Flushing active apps, app size: #{@flushing_apps.size}, msg size: #{zmsg.size}")
         EM.next_tick { NATS.publish('router.active_apps', zmsg) }
+
+        @flushing = false
       end
 
     end