Emulates a syslog server to push nginx request data to StatsD. A lot of this is fit for my implementation

nginx.conf

log_format json escape=json
  '{'
    '"timestamp":"$time_iso8601",'
    '"request_time":"$request_time",'
    '"request_time_ms":"$msec",'
    '"upstream_cache_status":"$upstream_cache_status",'
    '"remote_addr":"$remote_addr",'
    '"cf_connecting_ip":"$http_cf_connecting_ip",'
    '"range":"$http_range",'
    '"uri":"$uri",'
    '"args":"$args",'
    '"status":"$status",'
    '"bytes_sent":"$body_bytes_sent",'
    '"http_user_agent":"$http_user_agent",'
    '"http_host":"$http_host", '
  '}';

access_log syslog:server=127.0.0.1:8514 json;

syslog.ts

import { config } from 'dotenv';
import dgram from 'dgram';
import StatsD from './StatsD.js';

config({ path: '.env' });

const server = dgram.createSocket('udp4');

const statsd = new StatsD(process.env.STATSD_DSN, {
  prefix: '_',
  globalTags: { env: process.env.NODE_ENV || 'development' },
  errorHandler: (error) => console.error('StatsD error:', error)
});

interface RequestData {
  request_time: number;
  request_time_ms: number;
  bytes_sent: number;
  status: number;
  args: { key: string; value: string }[];
  timestamp: Date;
  host_ip?: string;
  uri: string;
  upstream_cache_status?: string;
}

const processMessage = (msg: Buffer, hostIP: string): void => {
  const json = msg.slice(msg.indexOf('{'), msg.lastIndexOf('}') + 1).toString();
  const data = JSON.parse(json) as RequestData;

  data.request_time = parseFloat(data.request_time?.toString() || '0');
  data.request_time_ms = parseFloat(data.request_time_ms?.toString() || '0') * 1000;
  data.bytes_sent = parseInt(data.bytes_sent?.toString() || '0');
  data.status = parseInt(data.status?.toString() || '0');
  
  data.args = (data.args as unknown as string).split('&').map(arg => {
    const [key, value] = arg.split('=');
    return { key, value };
  });

  data.timestamp = new Date(data.timestamp as unknown as string);
  data.host_ip = hostIP;

  statsd.gauge('bw.bytes', data.bytes_sent, {
    // Add whatever else here
    host_ip: data.host_ip,
    cache_status: data.upstream_cache_status,
  });
};

let messagesPerSec = 0;

setInterval(() => {
  console.log('Messages per sec:', Math.round(messagesPerSec / 5));
  messagesPerSec = 0;
}, 5000);

server.on('message', (msg: Buffer, rinfo: dgram.RemoteInfo) => {
  try {
    processMessage(msg, rinfo.address);
  } catch (e) {
    console.error(e);
  }
  messagesPerSec++;
});

server.bind(8514, process.env.LOG_BIND_IP || '127.0.0.1');

process.on('SIGINT', () => server.close());