Tell Me More, Nginx (2017)

Web servers are the workhorses of the internet, reliable and battle-hardened, but the logs are standard and never have anything of the interesting application metadata anyway. Upstream response headers (docs): Tuck useful metadata from your application into your HTTP response headers, and tell nginx to pull X-Whatever-You-Want out into your logs. User IDs, database timers, and server metadata—right alongside high-level, granular data surrounding each request.

Source: www.honeycomb.io