Serve DNS authoritative responses... with Erlang.
To build:
make
To start fresh:
make fresh
make
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.example.config
. Copy it to erldns.config
and modify as needed.
overmind start
./rebar3 shell
./rebar3 release
./_build/default/rel/erldns/bin/erldns foreground
Here are some queries to try:
dig -p 8053 @127.0.0.1 example.com a
dig -p 8053 @127.0.0.1 example.com cname
dig -p 8053 @127.0.0.1 example.com ns
dig -p 8053 @127.0.0.1 example.com mx
dig -p 8053 @127.0.0.1 example.com spf
dig -p 8053 @127.0.0.1 example.com txt
dig -p 8053 @127.0.0.1 example.com sshfp
dig -p 8053 @127.0.0.1 example.com soa
dig -p 8053 @127.0.0.1 example.com naptr
dig -p 8053 @127.0.0.1 -x 127.0.0.1 ptr
In our environment (DNSimple) we are seeing 30 to 65 µs handoff times to retrieve 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 <<"example.com">> 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:
erldns_zone_cache:put_zone({
<<"example.com">>, [
#dns_rr{
name = <<"example.com">>,
type = ?DNS_TYPE_A,
ttl = 3600,
data = #dns_rrdata_a{ip = {1,2,3,4}}
},
#dns_rr{
name = <<"www.example.com">>,
type = ?DNS_TYPE_CNAME,
ttl = 3600,
data = #dns_rrdata_cname{dname = <<"example.com">>}
}
]}).
Folsom is used to gather runtime metrics and statistics.
There is an HTTP API for querying metric data available at https://github.com/dnsimple/erldns-metrics
This project uses OpenTelemetry (OTEL) Tracing to provide telemetry data on request processing inside of erldns.
To enable opentelmetry tracing, you need to:
Configure the opentelemetry client:
Add the following configuration to the erldns.config:
{opentelemetry,[
{processors,
[{otel_batch_processor,
#{exporter => {opentelemetry_exporter, #{protocol => http_protobuf,
endpoints => [{http, "127.0.0.1", 55681, []}]}}}}]}
]}
NOTE: You will need to have a running OpenTelemetry Collector.
Application traces:
Name | Dimensions |
---|---|
erldns_tcp_worker | |
handle_tcp_dns_query | status, qr, rd, ad, qname, qtype |
handle_decoded_tcp_message | status |
send_tcp_message | |
erldns_udp_worker | host, port, erlang_port_count, erlang_proc_count, erlang_run_queue, erlang_proc_message_queue_len, status |
handle_udp_dns_query | status, qr, rd, ad, qname, qtype |
handle_decoded_udp_message | status |
synthesize_answer | |
encode_message | rcode, aa, ra, answers |
There is an administrative API for querying the current zone cache and for basic control. You can find it in https://github.com/dnsimple/erldns-admin