# Put log_format inside your http context. escape=json is important.
# Choose your own log destination; do not replace existing logs blindly.
log_format request_sieve escape=json
    '{"epoch":$msec,"host":"$host","uri":"$request_uri",'
    '"status":$status,"method":"$request_method"}';

# In the desired server context, after defining the format above:
# access_log /var/log/nginx/request-sieve.jsonl request_sieve;