View Source gc_discover_dns_ip (gen_cluster v0.3.0)

Discovery method that takes a host name to query DNS A records for and uses all the returned hosts as peers to connect or reconnect to. Whether to use the IP or the hostname associated with each IP result is configured with the option host_type which takes ip or hostname as values. The default is ip which uses the IP as is in the node name. When it is hostname each returned IP is passed to inet_res:gethostbyaddr/1 to get a hostname for the address.

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_ip. The alias dns covers both gc_discover_dns_ip and gc_discover_dns_srv. This method (gc_discover_dns_ip) is used by default and when the option record_type => ip 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, and that record_type defaults to ip:

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

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

To use IPv6 set ipv6 to true:

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

This results in the AAAA records of k8s-erlang-cluster.k8s-erlang-cluster being queried for.

Summary

Types

options()

Module options. Takes a domain to query for, an optional host_type which can be ip or hostname, a boolean ipv6 for whether to query for A or AAAA records and lookup_timeout which is the time each DNS query can take.

Functions

init/1
peers/1

Types

Link to this type

options()

View Source 
-type options() ::
          #{domain := gc_discover_dns:dns_name(),
            host_type => gc_discover_dns:host_type(),
            ipv6 => boolean(),
            lookup_timeout => erlang:timeout()}.

Module options. Takes a domain to query for, an optional host_type which can be ip or hostname, a boolean ipv6 for whether to query for A or AAAA records and lookup_timeout which is the time each DNS query can take.

Functions

Link to this function

init/1

View Source 
-spec init(options()) ->
              {ok,
               #state{node_name :: string(),
                      domain :: 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()}}.
Link to this function

peers/1

View Source 
-spec peers(#state{node_name :: string(),
                   domain :: 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().