» Out-of-Cluster Nodes
Non-Kubernetes nodes can join a Consul cluster running within Kubernetes. These are considered "out-of-cluster" nodes.
The recommended way to join a cluster running within Kubernetes is to use the "k8s" cloud auto-join provider.
The auto-join provider dynamically discovers IP addresses to join using
the Kubernetes API. It authenticates with Kubernetes using a standard
kubeconfig file. This works with all major hosted Kubernetes offerings
as well as self-hosted installations.
The auto-join string below will join a Consul server cluster that is started using the official Helm chart:
$ consul agent -retry-join 'provider=k8s label_selector="app=consul,component=server"'
By default, Consul will join the default Gossip port. Pods may set an
consul.hashicorp.com/auto-join-port to an integer value or
a named port to specify the port for the auto-join to return. This enables
different pods to have different exposed ports.
Consul typically requires a fully connected network. Therefore, out-of-cluster nodes joining a cluster running within Kubernetes must be able to communicate to pod IPs or Kubernetes node IPs via the network.
Consul Enterprise customers may use network segments to enable non-fully-connected topologies. However, out-of-cluster nodes must still be able to communicate with the server pod or host IP addresses.
The auto-join provider discussed above will use pod IPs by default. The
host_network=true setting may be set to use host IPs, however all the ports
Consul requires must be exposed via a
hostPort. If no ports are exposed via
hostPort, the pod will not be discovered.