nginx header logs

header-logging.conf

# Load JavaScript code from here
js_include conf.d/header_logging.js;

# Fill variable from JS function
js_set $access_log_with_headers kvAccessLog;

# Define special log format
log_format kvpairs $access_log_with_headers;

server {
  listen 80;
  access_log /var/log/nginx/access_headers.log kvpairs;
  location / {
    proxy_pass http://www.example.com;
  }
}

header-logging.js

function kvHeaders(headers, parent) {
  var kvpairs = ""
  for (var h in headers) {
    kvpairs += " " + parent + "." + h + "="
    if (headers[h].indexOf(" ") == -1) {
      kvpairs += headers[h]
    } else {
      kvpairs += "'" + headers[h] + "'"
    }
  }
  return kvpairs
}

function kvAccessLog(r) {
  var log = r.variables.time_iso8601    // NGINX JavaScript can access all variables
  log += " client=" + r.remoteAddress   // Property of request object
  log += " method=" + r.method          // "
  log += " uri=" + r.uri                // "
  log += " status=" + r.status          // Property of response object
  log += kvHeaders(r.headersIn, "in")  // Send request headers object to function
  log += kvHeaders(r.headersOut, "out") // Send response headers object to function
  return log
}