Create and Manage Cluster Peering Connections

A peering token enables cluster peering between different datacenters. Once you generate a peering token, you can use it to establish a connection between clusters. Then you can export services and authorize other clusters to call those services.

To peer clusters, you must complete the following steps in order:

1. Create a peering token
2. Establish a connection between clusters
3. Export service endpoints
4. Authorize connections between peers

Create a peering token

You can generate peering tokens and initiate connections using the Consul API on any available agent. However, we recommend performing these operations through a client agent in the partition you want to connect.

To begin the cluster peering process, generate a peering token in one of your clusters. The other cluster uses this token to establish the peering connection.

In cluster-01, issue a request for a peering token using the HTTP API.

$ curl --request POST --data '{"PeerName":"cluster-02"}' --url http://localhost:8500/v1/peering/token

The CLI outputs the peering token, which is a base64-encoded string containing the token details.

Create a JSON file that contains the first cluster's name and the peering token.

{
    "PeerName": "cluster-01",
    "PeeringToken": "eyJhbGciOiJIUzI1NiJ9.eyJzdWIiOiJhZG1pbiIsImF1ZCI6IlNvbHIifQ.5T7L_L1MPfQ_5FjKGa1fTPqrzwK4bNSM812nW6oyjb8"
}

Establish a connection between clusters

Next, use peering_token.json to establish a secure connection between the clusters. In the client agents of "cluster-02," establish the peering connection using the HTTP API. This endpoint does not generate an output unless there is an error.

$ curl --request POST --data @peering_token.json http://127.0.0.1:8500/v1/peering/establish

When you connect server agents through cluster peering, they peer their default partitions. To establish peering connections for other partitions through server agents, you must add the Partition field to peering_token.json and specify the partitions you want to peer. For additional configuration information, refer to Cluster Peering - HTTP API.

Export service endpoints

After you establish a connection between the clusters, you need to create a configuration entry that defines the services that are available for other clusters. Consul uses this configuration entry to advertise service information and support service mesh connections across clusters.

First, create a configuration entry and specify the Kind as "exported-services".

Kind = "exported-services"

Services = [
  {
    ## The name and namespace of the service to export.
    Name      = "service-name"
    Namespace = "default"

    ## The list of peer clusters to export the service to.
    Consumers = [
      {
        ## The peer name to reference in config is the one set
        ## during the peering process.
        Peer = "cluster-02"
      }
    ]

Then, add the configuration entry to your cluster.

$ consul config write peering-config.hcl

Before you proceed, wait for the clusters to sync and make services available to their peers. You can issue an endpoint query to check the peered cluster status.

Authorize connections from peers

Before you can call services from peered clusters, you must set service intentions that authorize those clusters to use specific services. Consul prevents services from being exported to unauthorized clusters.

First, create a configuration entry and specify the Kind as "service-intentions". Declare the service on "cluster-02" that can access the service in "cluster-01." The following example sets service intentions so that "frontend-service" can access "backend-service."

Kind      = "service-intentions"
Name      = "backend-service"

Sources = [
  {
    Name   = "frontend-service"
    Peer   = "cluster-02"
    Action = "allow"
  }
]

If the peer’s name is not specified in Peer, then Consul assumes that the service is in the local cluster.

Then, add the configuration entry to your cluster.

$ consul config write peering-intentions.hcl

Check peered cluster status

To confirm that you peered your clusters, you can query the /health/service endpoint of one cluster from the other cluster. For example, in "cluster-02," query the endpoint and add the peer=cluster-01 query parameter to the end of the URL.

$ curl \
    "http://127.0.0.1:8500/v1/health/service/<service-name>?peer=cluster-01"

A successful query will include service information in the output.

Remove peering connections

After you create a peering connection between clusters in different datacenters, you can disconnect the peered clusters. Deleting a peering connection stops data replication to the peer and deletes imported data, including services and CA certificates.

In "cluster-01," request the deletion via the HTTP API.

$ curl --request DELETE http://127.0.0.1:8500/v1/peering/cluster-02