Consul is used to manage endpoints and deliver a service discovery feature. The DNS interface is used in order to resolve hosts and service names. It also provides a REST interface that could be used by users or operators of the platform.
More information on the DNS interface for Consul can be found in the Consul DNS documentation
Each node in a PNDA Cluster includes a Consul agent. These agents register with a Consul server - a single one running on the Kafka instance for the pico flavor and a quorum running on the Zookeeper instances for standard. The agents automatically keep the DNS entries in the server up to date with any changes.
Hosts can be referenced with their hostname or full qualified domain name:
<hostname>.node.<datacenter>.<domain>
e.g.
pnda-kafka-0.node.dc1.pnda.local
or just
pnda-kafka-0
PNDA uses default values for datacenter and domain of dc1 and pnda.local.
Services can be referenced with:
<servicename>.service.<datacenter>.<domain>
The Consul DNS server is configured on each node in a PNDA cluster in resolv.conf. This defines the nameserver as the IP address where the server instance of Consul is running and the search domain as node.dc1.pnda.local. Here is a sample configuration:
[root@pnda-guide-14371-kafka-0 ec2-user]# cat /etc/resolv.conf
nameserver 10.0.1.98
# Generated by NetworkManager
search eu-west-1.compute.internal node.dc1.pnda.local
nameserver 10.0.0.2
Hostnames, fully qualified domain names, and service names can all be resolved from any node in the cluster, for example:
[root@pnda-guide-14371-bastion ec2-user]# ping pnda-guide-14371-kafka-0
PING pnda-guide-14371-kafka-0.node.dc1.pnda.local (10.0.1.98) 56(84) bytes of data.
[root@pnda-guide-14371-bastion ec2-user]# ping zookeeper.service.dc1.pnda.local
PING zookeeper.service.dc1.pnda.local (10.0.1.98) 56(84) bytes of data.
The Consul UI can be used to view the cluster topology:
