legitimate "bots" sending empty requests

[kruskall]

As part of the ops KPI review we've been investigating the following errors in ecs logs:

validation error: 'metadata' required

On closer inspection it looks like this is an empty request: http.request.body.bytes: 0

Besides sending empty request to APM Server, another interesting metric is that the majority of these requests are coming from "legitime bots":

• AdsBot-Google (+http://www.google.com/adsbot.html)
• Mozilla/5.0 [...] (compatible; Google-Read-Aloud; +https://support.google.com/webmasters/answer/1061943)
• Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; Googlebot/2.1; +http://www.google.com/bot.html) Chrome/114.0.5735.179 Safari/537.36
• Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)
• Mozilla/5.0 (Linux; Android 6.0.1; Nexus 5X Build/MMB29P) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/114.0.5735.179 Mobile Safari/537.36 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)
• Mozilla/5.0 (compatible; YandexRenderResourcesBot/1.0; +http://yandex.com/bots) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/108.0.0.0