nns

Node Name Server service

NNS service is a service that stores node-id to IP mapping. It exposes several interfaces to query and update the mapping:

1. GRPC interface
2. Prometheus HTTP targets config that can be used by Prometheus to scrape metrics from nodes. Available at /prometheus
3. DNS GRPC. Implementation of CoreDNS grpc plugin that could be integrated with CoreDNS to resolve node-id on DNS level. Useful for running in Kubernetes

CoreDNS Integration

NNS service acts as a CoreDNS grpc plugin that resolves A DNS requests only. Refer to CoreDNS documentation for more details.

Here is an example of CoreDNS config map that resolves all subdomains of .node.mesh via network service:

apiVersion: v1
data:
  Corefile: |
           node.mesh {
              errors
              log
              grpc . 172.20.224.224:9090
            }
           .:53 {
              errors
              health
              kubernetes cluster.local in-addr.arpa ip6.arpa {
                  pods insecure
                  fallthrough in-addr.arpa ip6.arpa
              }
              prometheus :9153
              forward    . /etc/resolv.conf
              cache 30
              loop
              reload
              loadbalance
              }
kind: ConfigMap
metadata:
  labels:
    eks.amazonaws.com/component: coredns
    k8s-app: kube-dns
  name: coredns
  namespace: kube-system

172.20.224.224 is the IP of the Net service running in cluster

Running Locally

1. Build the app: make build
2. Run docker-compose docker-compose up --build
3. Add DNS record to etcd: docker exec -it etcd etcdctl put uk-sa2203-hnode-a1-0a16 172.10.0.1
4. Login to bastion: docker exec -it bastion bash
5. Check the resolution of node's hostname dig -p 53 @coredns uk-sa2203-hnode-a1-0a16.node.mesh

...
;; ANSWER SECTION:
uk-sa2203-hnode-a1-0a16.node.mesh. 0 IN A       172.10.0.1
...