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DNS server, in erlang.
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aeden Merge pull request #75 from dnsimple/bugfix/not-a-question
Drop messages that are received with the qr bit set to 1
Latest commit 22e8320 Apr 15, 2019
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include Use maps for named index May 16, 2017
priv Merge branch 'master' into bug/zonecut-respond-with-zonecut-delegation Dec 12, 2018
src Merge branch 'master' into bugfix/not-a-question Apr 15, 2019
.gitignore Ignore rebar3 generated files Nov 4, 2016
LICENSE.markdown Update license Jul 20, 2018
Makefile Switch to rebar3 Apr 21, 2018
Procfile Clean up Sep 7, 2012
README.markdown Update README links from aetrion to dnsimple (#84) Oct 18, 2018 Removed dependency. Mar 11, 2013
erldns.config.example Clean up example config so the app launches properly Jan 5, 2017
rebar.config Switch to rebar3 Apr 21, 2018
rebar3 Switch to rebar3 Apr 21, 2018 Fix Apr 26, 2018 Adding tests. Oct 10, 2013


Erlang DNS Server

Serve DNS authoritative responses...with Erlang.

Build Status


To build clean:


If you've already built once and just want to recompile the erl-dns source:

./rebar compile


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.


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

Copy it to erldns.config and modify as needed.


Launch directly:

erl -config erldns.config -pa ebin -pa deps/**/ebin -s erldns

Or use Foreman:

foreman start


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


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.


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 = <<"">>}


Folsom is used to gather runtime metrics and statistics.

There is an HTTP API for querying metric data available at


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

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