Overview

This interface supports integration between designate-bind and prometheus-bind-exporter-operator.

Usage

Layer

To consume this interface in your charm or layer, add the following to layer.yaml:

includes: ['interface:bind-client']

Provides

Add a provides interface of type bind-client to your charm or layers metadata.yaml:

provides:
  dns-backend:
    interface: bind-rndc
  bind-stats:
    interface: bind-client

• Note that charm-designate-bind normally works with charm-designate with the bind-rndc interface.

flag: {relation_name}.connected

This flag is set when the bind-exporter unit is joined and removes when departed, or broken.

For example, the following code is used in charm-designate-bind and the charm may not use a bind-exporter. When the bind-exporter is not present, the flag {relation_name}.connected won't be set and the templates will react accordingly with this.

When the flag {relation_name}.connected is set, it will create a new file /etc/bind/stats.conf in charm-designate-bind with the following content:

statistics-channels {
  inet <stats-listen-net> port <stats-port> allow { <client-ip>; };
};

It will also include this new file at etc/bind/named.conf. This will open a statistics channel in bind that bind-exporter can expose metrics to collect.

When the flag is not set, the statistics channel is closed.

If the bind-exporter is present in the bundle, it will check if configuration has changed and send this information through the endpoint of the relation.

import charm.openstack.designate_bind as designate_bind

@reactive.when('rndckey.available')
@reactive.when('dns-backend.related')
def config_changed():
    '''Render configs and restart services if necessary.'''

    dns_backend_endpoint = reactive.endpoint_from_flag("dns-backend.related")
    bind_stats_endpoint = reactive.endpoint_from_name("bind-stats")

    if reactive.is_flag_set('bind-stats.connected'):
        config = hookenv.config()
        if config.changed("stats-port"):
            bind_stats_endpoint.configure(
                ip='127.0.0.1', port=hookenv.config('stats-port')
            )

    designate_bind.set_apparmor()
    designate_bind.render_all_configs(
        [dns_backend_endpoint, bind_stats_endpoint]
    )

Requires

Add a requires interface of type bind-client to your charm or layers metadata.yaml:

requires:
  bind-stats:
    interface: bind-client

flag: {relation_name}.connected

This flag is set when the bind-exporter unit is joined and removes when departed, or broken.

@reactive.when('bind-stats.connected')
def start_bind_exporter():

    bind_stats_endpoint = reactive.endpoint_from_flag("bind-stats")
    config = bind_stats_endpoint.get_config()
    # logic to start the bind exporter