prometheus

prometheus enables Prometheus metrics.

Description

With prometheus you export metrics from CoreDNS and any plugin that has them. The default location for the metrics is localhost:9153. The metrics path is fixed to /metrics. The following metrics are exported:

  • coredns_build_info{version, revision, goversion} - info about CoreDNS itself.
  • coredns_dns_request_count_total{server, zone, proto, family} - total query count.
  • coredns_dns_request_duration_seconds{server, zone} - duration to process each query.
  • coredns_dns_request_size_bytes{server, zone, proto} - size of the request in bytes.
  • coredns_dns_request_do_count_total{server, zone} - queries that have the DO bit set
  • coredns_dns_request_type_count_total{server, zone, type} - counter of queries per zone and type.
  • coredns_dns_response_size_bytes{server, zone, proto} - response size in bytes.
  • coredns_dns_response_rcode_count_total{server, zone, rcode} - response per zone and rcode.

Each counter has a label zone which is the zonename used for the request/response.

Extra labels used are:

  • server is identifying the server responsible for the request. This is a string formatted as the server’s listening address: <scheme>://[<bind>]:<port>. I.e. for a “normal” DNS server this is dns://:53. If you are using the bind plugin an IP address is included, e.g.: dns://127.0.0.53:53.
  • proto which holds the transport of the response (“udp” or “tcp”)
  • The address family (family) of the transport (1 = IP (IP version 4), 2 = IP6 (IP version 6)).
  • type which holds the query type. It holds most common types (A, AAAA, MX, SOA, CNAME, PTR, TXT, NS, SRV, DS, DNSKEY, RRSIG, NSEC, NSEC3, IXFR, AXFR and ANY) and “other” which lumps together all other types.
  • The response_rcode_count_total has an extra label rcode which holds the rcode of the response.

If monitoring is enabled, queries that do not enter the plugin chain are exported under the fake name “dropped” (without a closing dot - this is never a valid domain name).

This plugin can only be used once per Server Block.

Syntax

prometheus [ADDRESS]

For each zone that you want to see metrics for.

It optionally takes an address to which the metrics are exported; the default is localhost:9153. The metrics path is fixed to /metrics.

Examples

Use an alternative address:

. {
    prometheus localhost:9253
}

Or via an enviroment variable (this is supported throughout the Corefile): export PORT=9253, and then:

. {
    prometheus localhost:{$PORT}
}

Bugs

When reloading, we keep the handler running, meaning that any changes to the handler’s address aren’t picked up. You’ll need to restart CoreDNS for that to happen.