---
title: DNS
---

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* [service discovery via DNS](#service-discovery-via-dns)

## service discovery via DNS

Some service discovery system, like Consul, support exposing service information
via DNS. Therefore we can use this way to discover service directly.

First of all, we need to configure the address of DNS servers:

```yaml
# add this to config.yaml
discovery:
   dns:
     servers:
       - "127.0.0.1:8600"          # use the real address of your dns server
```

Unlike configurating domain in the Upstream's `nodes` field, service discovery via
DNS will return all records. For example, with upstream configuration:

```json
{
    "id": 1,
    "discovery_type": "dns",
    "service_name": "test.consul.service",
    "type": "roundrobin"
}
```

and `test.consul.service` be resolved as `1.1.1.1` and `1.1.1.2`, this result will be the same as:

```json
{
    "id": 1,
    "type": "roundrobin",
    "nodes": {
        {"host": "1.1.1.1", "weight": 1},
        {"host": "1.1.1.2", "weight": 1}
    }
}
```

Note that all the IPs from `test.consul.service` share the same weight.

If a service has both A and AAAA records, A record is preferred.
Currently we support A / AAAA records, SRV has not been supported yet.

If you want to specify the port for the upstream server, you can add it to the `service_name`:

```json
{
    "id": 1,
    "discovery_type": "dns",
    "service_name": "test.consul.service:1980",
    "type": "roundrobin"
}
```