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Implement an ingress gateway

This topic describes how to add ingress gateways to your Consul service mesh. Ingress gateways enable connectivity within your organizational network by allowing services outside of the service mesh to send traffic to services in the mesh. Refer to Ingress gateways overview for additional information about ingress gateways.

This topic describes ingress gateway usage for virtual machine (VM) environments. Refer to Configure ingress gateways for Consul on Kubernetes for instructions on how to implement ingress gateways in Kubernetes environments.

Overview

Ingress gateways are a type of proxy service included with Consul. Complete the following steps to set up an ingress gateway:

  1. Define listeners and the services they expose. Specify these details in an ingress gateway configuration entry.
  2. Register an ingress gateway service. Define the services in a service definition file.
  3. Start the ingress gateway. This step deploys the Envoy proxy that functions as the ingress gateway.

After specifying listeners and services in the ingress gateway configuration entry, you can register the gateway service and start Envoy with a single CLI command instead of completing these steps separately. Refer Register an ingress service on Envoy startup.

Requirements

ACL requirements

If ACLs are enabled, you must present a token when registering ingress gateways that grant the following permissions:

service:write for the ingress gateway's service name service:read for all services in the ingress gateway's configuration entry node:read for all nodes of the services in the ingress gateway's configuration entry.

These privileges authorize the token to route communications to other services in the mesh. If the Consul client agent on the gateway's node is not configured to use the default 8502 gRPC port, then the gateway's token must also provide agent:read for its node's name in order to discover the agent's gRPC port. gRPC is used to expose Envoy's xDS API to Envoy proxies.

Expose services

Define and apply an ingress gateway configuration entry to specify which services in the mesh to expose to external services.

Define an ingress gateway configuration entry

Ingress gateway configuration entries map downstream ingress listeners to upstream services. When you register an ingress gateway proxy that matches the configuration entry name, Consul applies the settings specified in the configuration entry. Configure the following fields:

  • Kind: Set the value to ingress-gateway.
  • Name: Consul applies the configuration entry settings to ingress gateway proxies with names that match the Name field.
  • Listeners: Specify one or more listeners.
    • Listeners.Port: Specify a port for the listener. Each listener is uniquely identified by its port number.
    • Listeners.Protocol: The default protocol is tcp, but you must specify the protocol used by the services you want to allow traffic from.
    • Listeners.Services: The Services field contains the services that you want to expose to upstream services. The field contains several options and sub-configurations that enable granular control over ingress traffic, such as health check and TLS configurations.

For Consul Enterprise service meshes, you may also need to configure the Partition and Namespace fields for the gateway and for each exposed service.

Refer to Ingress gateway configuration entry reference for details about the supported parameters.

Register an ingress gateway configuration entry

You can register the configuration entry using the consul config command or by calling the /config API endpoint. Refer to How to Use Configuration Entries for details about applying configuration entries.

The following example registers an ingress gateway configuration entry named public-ingress.hcl that is stored on the local system:

$ consul config write public-ingress.hcl

Deploy an ingress gateway service

To deploy an ingress gateway service, create a service definition and register it with Consul.

You can also define an ingress gateway service and register it with Consul while starting an Envoy proxy from the command line. Refer to Register an ingress service on Envoy startup for details.

Create a service definition for the ingress gateway

Consul applies the settings defined in the ingress gateway configuration entry to ingress gateway services that match the configuration entry name. Refer to Define services for additional information about defining services in Consul.

The following fields are required for the ingress gateway service definition:

  • Kind: The field must be set to ingress-gateway.
  • Name: The name should match the value specified for the Name field in the configuration entry.

All other service definition fields are optional, but we recommend defining health checks to verify the health of the gateway. Refer to Services configuration reference for information about defining services.

Register the ingress gateway proxy service

You can register the ingress gateway using API or CLI. Refer to Register services and health checks for instructions on registering services in Consul.

The following example registers an ingress gateway defined in ingress-gateway.hcl from the Consul CLI:

$ consul services register ingress-service.hcl

Start an Envoy proxy

Run the consul connect envoy command to start Envoy. Specify the name of the ingress gateway service and include the -gateway=ingress flag. Refer to Consul Connect Envoy for details about using the command.

The following example starts Envoy for the ingress-service gateway service:

$ consul connect envoy -gateway=ingress ingress-service

Register an ingress service on Envoy startup

You can also automatically register the ingress gateway service when starting the Envoy proxy. Specify the following flags with the consul connect envoy command:

The following example starts Envoy and registers an ingress gateway service named ingress-service bound to the agent address at port 8888: 

$ consul connect envoy -gateway=ingress -register \
   -service ingress-service \
   -address '{{ GetInterfaceIP "eth0" }}:8888'

You cannot register the ingress gateway service and start the proxy at the same time if you configure the gateway to retrieve and serve TLS certificates from their external downstreams. Refer to Serve custom TLS certificates from an external service for more information.

Additional Envoy configurations

Ingress gateways support additional Envoy gateway options and escape-hatch overrides. Specify gateway options in the ingress gateway service definition to use them. To use escape-hatch overrides, you must add them to your global proxy defaults configuration entry. Refer to the following documentation for additional information:

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