# Erlang DNS Server

Serve DNS authoritative responses...with Erlang.

[![Build Status](](

## Building

To build:


To start fresh:

  make fresh

## Zones

Zones are loaded from JSON.

Example JSON files are in the priv/ directory.

You can also write new systems to load zones by writing the zones directly to the zone cache using `erldns_zone_cache:put_zone/1`.

## Configuration

An example configuration file can be found in erldns.config.example.

Copy it to erldns.config and modify as needed.

## Running

Launch directly:

    rebar3 shell

Or use Foreman:

    foreman start

## Querying

Here are some queries to try:

    dig -p8053 @ a
    dig -p8053 @ cname
    dig -p8053 @ ns
    dig -p8053 @ mx
    dig -p8053 @ spf
    dig -p8053 @ txt
    dig -p8053 @ sshfp
    dig -p8053 @ soa
    dig -p8053 @ naptr

    dig -p8053 @ -x ptr

## Performance

In our environment (DNSimple) we are seeing 30 to 65 µs handoff times to retreive a packet from the UDP port and give it to a worker for processing. Your performance may vary, but given those measurements erl-dns is capable of handling between 15k and 30k questions per second. Please note: You may need to configure the number of workers available to handle traffic at higher volumes.

## Design

The `erldns_resolver` module will attempt to find zone data in the zone cache. If you're embedding erl-dns in your application the easiest thing to do is to load the zone cache once the zone cache `gen_server` starts push an updated zone into the cache each time data changes.

To insert a zone, use `erldns_zone_cache:put_zone({Name, Records})` where Name is a binary term such as <<"">> and Records is a list of `dns_rr` records (whose definitions can be found in `deps/dns/include/dns_records.hrl`). The name of each record must be the fully qualified domain name (including the zone part).

Here's an example:

  <<"">>, [
      name = <<"">>,
      type = ?DNS_TYPE_A,
      ttl = 3600,
      data = #dns_rrdata_a{ip = {1,2,3,4}}
      name = <<"">>,
      type = ?DNS_TYPE_CNAME,
      ttl = 3600,
      data = #dns_rrdata_cname{dname = <<"">>}

## Metrics

Folsom is used to gather runtime metrics and statistics.

There is an HTTP API for querying metric data available at

## Admin

There is a administrative API for querying the current zone cache and for basic control. You can find it in