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05-consul.md

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Consul

Consul is a distributed key/value store that provides service discovery and health checking in a Nomad cluster. In this section three Consul servers will be deployed as part of the Nomad control plane.

Provision the Consul Servers

Consul will be configured to store cluster state on network attached volumes. The network attached volumes will be dynamically provisioned and managed by Kubernetes.

Create the consul ConfigMap which holds the Consul server and client configuration:

kubectl apply -f configmaps/consul.yaml

Create the consul StatefulSet which will manage the Consul servers and ensure they have stable storage and DNS names:

kubectl apply -f statefulsets/consul.yaml

It will take a few minutes to provision the Consul cluster. Use the kubectl command to monitor progress:

kubectl get pods -l app=consul

NAME       READY     STATUS    RESTARTS   AGE
consul-0   0/1       Pending   0          5s

Estimated time to completion: 2 minutes.

kubectl get pods -l app=consul

NAME       READY     STATUS    RESTARTS   AGE
consul-0   1/1       Running   0          1m
consul-1   1/1       Running   0          1m
consul-2   1/1       Running   0          39s

Delegate the consul domain to Consul

The internal Kubernetes DNS service can be configured to delegate specific domains to another DNS server such as Consul. This enables Consul to handle all DNS queries to the consul. domain, while Kubernetes handles everything else.

Update the kube-dns ConfigMap to delegate the consul. domain to the Consul cluster:

cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: ConfigMap
metadata:
  labels:
    addonmanager.kubernetes.io/mode: EnsureExists
  name: kube-dns
  namespace: kube-system
data:
  stubDomains: |
    {"consul": ["$(kubectl get svc consul-dns -o jsonpath='{.spec.clusterIP}')"]}
EOF

Next: Provision The Vault Service