I'm new in the world of elastic. I would like to know if it is possible with watcher to get some variables and use it in "Message" (example: slack). I would like to create a watcher that send me a message on slack when I get HTTP server down. I'm ok with that but I don't know how to get url.full and http.response.status_code from my hearbeat-* indice. So if someone can give me documentation or little explanation to guide my search.