README.md

dns2

Performance and Benchmarking

Running the benchmark

A UDP throughput benchmark is included. It starts an in-process echo server, fires queries at it, and reports RPS and latency percentiles:

node benchmark/udp.js

# Tune via env vars
TOTAL=50000 CONCURRENCY=200 node benchmark/udp.js

# Target an external server
DNS=127.0.0.1:5353 node benchmark/udp.js

Example output on a modern laptop (single Node.js process, loopback UDP):

Sending 10000 queries at concurrency 100...

Results
-------
  Total queries : 10000
  Errors        : 0
  Wall time     : 812 ms
  Throughput    : 12315 req/s

  Latency (ms)
    min  : 0
    mean : 7.92
    p50  : 7
    p90  : 13
    p99  : 24
    max  : 61

Limiting concurrency with maxConcurrent

Use the maxConcurrent option on createServer to cap how many handler invocations can be in flight simultaneously. Requests that arrive when the limit is already reached receive an immediate SERVFAIL response rather than queuing unboundedly.

const server = dns2.createServer({
  udp: true,
  maxConcurrent: 500, // at most 500 handler calls in flight at once
  handle(request, send) {
    // async work here...
  },
});

Note: handlers must always call send() — the active-request counter decrements only when send() is invoked. A handler that never calls send() will permanently consume one concurrency slot.

Node.js tuning tips

• Run multiple worker processes with the built-in cluster module to use all CPU cores.
• Increase the V8 new-space size to reduce minor-GC frequency under high load: node --max-semi-space-size=64 server.js
• For production, consider a process manager (PM2, systemd) that auto-restarts on failure and enables multi-instance clustering.