Register services running on external nodes to Consul on Kubernetes
This page provides an overview for registering services in the Consul catalog when the service runs on a node that is not part of the Kubernetes cluster.
Introduction
Because Kubernetes has built-in service discovery capabilities, Consul on Kubernetes includes components such as Consul dataplanes and service sync so that operators can continue to use Kubernetes tools and processes. However, this approach to service networking still requires a service to run on a node that Consul is aware of, either through a local Consul client agent or the Kubernetes cluster. We call services that run on external nodes that Consul cannot automatically recognize external services.
Previously, the only way to register an external service when running Consul on Kubernetes was using Consul's HTTP API. This approach requires additional ACLs and direct access to Consul's HTTP API endpoint. Consul now supports registering external services and their associated health checks in the Consul catalog using a Registration custom resource definition (CRD) that follows the format of Consul's service definitions.
Workflows
The process to register an external service in Consul on Kubernetes consists of the following steps:
- Start Consul ESM. You must use Consul ESM to run health checks on external services.
- Define the external service and its health checks in a
RegistrationCRD. - Apply the CRD to your Kubernetes cluster. Internally, this action triggers an API call to Consul's
/catalog/registerendpoint to register the service. - When using Consul's service mesh, you should also:
- Deploy a terminating gateway so that downstream services can communicate with the external service.
- Define service intentions for the external service and the downstream services that communicate with it.
Guidance
The following resources are available to help you register external services to Consul on Kubernetes.