What is Cluster Peering?

Cluster peering is currently in technical preview: Functionality associated with cluster peering is subject to change. You should never use the technical preview release in secure environments or production scenarios. Features in technical preview may have performance issues, scaling issues, and limited support.

You can create peering connections between two or more independent clusters so that services deployed to different partitions or datacenters can communicate.

Overview

Cluster peering allows Consul clusters in different datacenters to communicate with each other. The cluster peering process consists of the following steps:

Create a peering token to share with other clusters
Establish a connection between clusters
Make services available to other clusters

For detailed instructions on setting up cluster peering with the Consul CLI, refer to Create and Manage Peering Connections.

Differences between WAN federation and cluster peering

WAN federation and cluster peering are different ways to connect clusters. The most important distinction is that WAN federation assumes clusters are owned by the same operators, so it maintains and replicates global states such as ACLs and configuration entries. As a result, WAN federation requires a primary datacenter to serve as an authority for replicated data.

Regardless of whether you connect your clusters through WAN federation or cluster peering, human and machine users can use either method to discover services in other clusters or dial them through the service mesh.

	WAN Federation	Cluster Peering
Connects clusters across datacenters	✅	✅
Shares support queries and service endpoints	✅	✅
Connects clusters owned by different operators	❌	✅
Functions without declaring primary datacenter	❌	✅
Shares key/value stores	✅	❌
Uses gossip protocol	✅	❌

Technical preview constraints

Not all features and functionality are available in the technical preview release. In particular, consider the following technical constraints:

Consul ACLs must be disabled or the ACL default_policy must be set to allow.
Mesh gateways for server to server traffic are not available. However, mesh gateways for service to service traffic between clusters are available.
Services exported to peered clusters must be configured to use the TCP protcol (not HTTP, HTTP 2 and gRPC).
Support for dynamic routing such as splits, custom routes, or redirects is not available.
The consul intention CLI command is not supported. To manage intentions that specify services in peered clusters, use configuration entries.
L7 permissions are not supported.
Configuring service failover across peers is not supported.
Accessing key/value stores across peers is not supported.
Consul datacenters that are already federated stay federated.
Non-enterprise Consul instances cannot sync services with namespaces outside of the default namespace.