DocsEdge StackService discovery and resolvers
Service discovery and resolvers
Service discovery is how cloud applications and their microservices are located on the network. In a cloud environment, services are ephemeral, existing only as long as they are needed and in use, so a real-time service discovery mechanism is required. Ambassador Edge Stack uses information from service discovery to determine where to route incoming requests.
Ambassador Edge Stack support for service discovery
Ambassador Edge Stack supports different mechanisms for service discovery. These mechanisms are:
- Kubernetes service-level discovery (default).
- Kubernetes endpoint-level discovery.
- Consul endpoint-level discovery.
Kubernetes service-level discovery
By default, Ambassador Edge Stack uses Kubernetes DNS and service-level discovery. In a
Mapping resource, specifying
service: foo will prompt Ambassador Edge Stack to look up the DNS address of the
foo Kubernetes service. Traffic will be routed to the
foo service. Kubernetes will then load balance that traffic between multiple pods. For more details on Kubernetes networking and how this works, see our blog post on Session affinity, load balancing controls, gRPC-Web, and Ambassador Edge Stack.
Kubernetes endpoint-level discovery
Ambassador Edge Stack can also watch Kubernetes endpoints. This bypasses the Kubernetes service routing layer and enables the use of advanced load balancing controls such as session affinity and maglev. For more details, see the load balancing reference.
Consul endpoint-level discovery
Ambassador Edge Stack natively integrates with Consul for endpoint-level service discovery. In this mode, Ambassador Edge Stack obtains endpoint information from Consul. One of the primary use cases for this architecture is in hybrid cloud environments that run a mixture of Kubernetes services as well as VMs, as Consul can serve as the single global registry for all services.
The Resolver resource
Resolver resource is used to configure the discovery service strategy for Ambassador Edge Stack.
The Kubernetes service resolver
The Kubernetes Service Resolver configures Ambassador Edge Stack to use Kubernetes services. If no resolver is specified, this behavior is the default. When this resolver is used, the
service.namespace value from a
Mapping is handed to the Kubernetes cluster's DNS resolver to determine where requests are sent.
The Kubernetes endpoint resolver
The Kubernetes Endpoint Resolver configures Ambassador Edge Stack to resolve Kubernetes endpoints. This enables the use of more a advanced load balancing configuration. When this resolver is used, the endpoints for the
service defined in a
Mapping are resolved and used to determine where requests are sent.
The Consul resolver
The Consul Resolver configures Ambassador Edge Stack to use Consul for service discovery. When this resolver is used, the
service defined in a
Mapping is passed to Consul, along with the datacenter specified, to determine where requests are sent.
address: The fully-qualified domain name or IP address of your Consul server. This field also supports environment variable substitution.
datacenter: The Consul data center where your services are registered
You may want to use an environment variable if you're running a Consul agent on each node in your cluster. In this setup, you could do the following:
and then add the
HOST_IP environment variable to your Kubernetes deployment:
Once a resolver is defined, you can use them in a given
The YAML configuration above will configure Ambassador Edge Stack to use Kubernetes Service Discovery to route to the Consul Service Discovery to route to the
bar service on requests with