update to monitoring script

script/queue_size.rb

@@ -3,5 +3,5 @@ require_relative '../lib/postal/config'
 require 'mysql2'
 client = Mysql2::Client.new(:host => Postal.config.main_db.host, :username => Postal.config.main_db.username, :password => Postal.config.main_db.password, :port => Postal.config.main_db.port, :database => Postal.config.main_db.database)
-result = client.query("SELECT COUNT(id) as size FROM `queued_messages` WHERE retry_after IS NULL OR retry_after <= ADDTIME(UTC_TIMESTAMP(), '30')")
+result = client.query("SELECT COUNT(id) as size FROM `queued_messages` WHERE retry_after IS NULL OR retry_after <= ADDTIME(UTC_TIMESTAMP(), '30') AND locked_at IS NULL")
 puts result.to_a.first['size']