View Source gc_discover_dns_srv (gen_cluster v0.3.0)

Discovery method that takes a host name to query DNS SRV records for and uses all the returned hosts as peers to connect or reconnect to. Whether to use the hostname or IP for each hostname result is configured with the option host_type which takes hostname or ip as values. The default is hostname which keeps the result as is in the node name. When it is ip each returned hostname is passed to inet_res:getbyname/3 to get an IP.

Since this is a built-in discovery module it has an alias, dns, which can be used in place of the full module name, gc_discovery_dns_srv. The alias dns covers both gc_discover_dns_ip and gc_discover_dns_srv. This module (gc_discover_dns_srv) is used when the option record_type => srv is given.

The name part of the node name to connect to is taken from the current node's name.

The following is an example relying on the alias, dns:

{gen_cluster, [{discovery, {dns, #{record_type => srv,
                                   domain => "k8s-erlang-cluster.k8s-erlang-cluster"}}}]}

This results in the SRV records for k8s-erlang-cluster.k8s-erlang-cluster being queried for every gen_cluster refresh interval and it tries to establish connections to those not already connected to.

To use IPv6 addresses as the host part of each node name set both host_type to ip and ipv6 to true:

{gen_cluster, [{discovery, {dns, #{record_type => srv,
                                   domain => "k8s-erlang-cluster.k8s-erlang-cluster",
                                   host_type => ip,
                                   ipv6 => true}}}]}

Summary

Types

options()

Module options. Takes domain, the domain to query for, an optional host_type which can be ip or hostname, the optional boolean ipv6 for whether to query for A or AAAA record when host_type is ip and optional lookup_timeout which is the time each DNS query can take (defaults to 5000 milliseconds).

Functions

init/1

peers/1

Types

options()

-type options() ::
          #{domain := string(),
            host_type => gc_discover_dns:host_type(),
            ipv6 => boolean(),
            lookup_opts => [inet_res:res_option()]}.

Functions

init/1

-spec init(options()) ->
              {ok,
               #state{node_name :: string(),
                      srv :: gc_discover_dns:dns_name(),
                      host_type :: gc_discover_dns:host_type(),
                      ip_record_type :: gc_discover_dns:ip_record_type(),
                      lookup_timeout :: erlang:timeout()}}.

peers/1

-spec peers(#state{node_name :: string(),
                   srv :: gc_discover_dns:dns_name(),
                   host_type :: gc_discover_dns:host_type(),
                   ip_record_type :: gc_discover_dns:ip_record_type(),
                   lookup_timeout :: erlang:timeout()}) ->
               gen_cluster:peers().