cluster: Add cluster peers DNS refresh job (#1428)
cluster: Add cluster peers DNS refresh job (#1428)

Adds a job which runs periodically and refreshes cluster.peer dns records.

The problem is that when you restart all of the alertmanager instances in an environment like Kubernetes, DNS may contain old alertmanager instance IPs, but on startup (when Join() happens) none of the new instance IPs. As at the start DNS is not empty resolvePeers waitIfEmpty=true, will return and "islands" of 1 alertmanager instances will form.

Signed-off-by: Povilas Versockas <bebb224104113522fff3b8e93eba9d0814b47f9c@gmail.com>
GoogleCloudPlatform/alertmanager,prometheus/alertmanager,prometheus/alertmanager,prometheus/alertmanager,GoogleCloudPlatform/alertmanager,GoogleCloudPlatform/alertmanager,GoogleCloudPlatform/alertmanager,prometheus/alertmanager