Extend logs

[dennis-tra]

These fields are already logged by nginx. We're just piping them through.

@iand quick questions:

• the referer field is empty. Is http_referer the wrong field here?
• The addr field contains cloudflare IP's and not client IP's. Should we rather use realip_remote_addr instead of remote_addr here? Will pointed me to this line.
• Would the upstream_cache_status field be populated in nginx_conf_ipfs? If so, I'd love to add that there as well. I can also ask in that bifrost-infra repo 👍

[WYiluo]

Just realize after today's meeting. I gusee the response time is the latency, say, the time to get the first byte.

We may also want the response complete time, that is, the time to get the last byte.

The response time should be compared with DHT walk duration, and the response complete should be compared with the total content fetch duration from an IPFS node.