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Consul API Gateway on Nomad

What is this?

An API Gateway is used for controlling access at entry and traffic management. You can read more about it the API gateways overview documentation.

This repository contains a working example of how to deploy an API Gateway using Consul and Nomad. It includes the following:

  1. Consul ACL roles, policies, and intentions for the API Gateway.
  2. Nomad job specifications to deploy the API Gateway and an example upstream application.
  3. A quick setup for trying it all out locally. This setup is similar to a production-grade deployment with mTLS enabled for both Consul and Nomad, but runs only on a single node.

This example uses Nomad's Workload Identity to authorize a Consul task to bootstrap the Envoy gateway task and correctly register it with Consul. The API Gateway is deployed in its own Nomad namespace. You'll add a Consul ACL role that the Consul binding rule matches for that Nomad namespace. That Consul ACL role grants the appropriate permissions to the API Gateway.

Local quickstart setup

If you already have running Nomad and Consul clusters with Workload Identity as described in the Consul ACL with Nomad Workload Identities tutorial, you can skip this section.

quickstart

This quickstart guide assumes that you have both Consul and Nomad installed and on your PATH.

  1. Set environment variables.

If you have go-sockaddr installed, the rest of the setup will use it to automatically get the correct IP address. If you do not, set it in your shell session:

export NODE_IP=<< private IP address >>
  1. Create certificates, root tokens, and TLS configuration.
cd quickstart
make

This will create TLS certificates for local use, as well as Nomad and Consul TLS agent configurations.

  1. Start Consul. In a new terminal window, navigate to the quickstart directory again, and start Consul in dev mode
consul agent -dev -config-file=./secrets/consul-agent.hcl
  1. Configure Consul CLI. Go back to the previous terminal window, and set your environment to configure the Consul CLI to talk to the Consul agent. Note that this command is surrounded by $(...) to run in a subshell to export the environment correctly.
$(make consul-env)

You can see the environment variables this has created by running env | grep CONSUL. It will include the CONSUL_HTTP_ADDR, the CONSUL_HTTP_TOKEN, and variables for the certificate paths.

  1. Setup Initial Consul ACLs.

Create a default Consul agent policy, and set the token for the Consul agent:

consul acl policy create -name "consul-agent" \
    -description "Consul Agent Policy" \
    -rules @acls/consul-agent-policy.hcl

consul acl token create -description="agent token" \
    -policy-name consul-agent \
    -secret=$(cat secrets/tokens/consul-agent)

Create a Consul ACL policy for the Nomad agent, and a token for the Nomad agent:

consul acl policy create -name "nomad-agent" \
    -description "Nomad Agent Policy" \
    -rules @acls/nomad-agent-policy.hcl

consul acl token create \
    -policy-name "nomad-agent" \
    -description "Nomad Agent Token" \
    -secret=$(cat secrets/tokens/nomad-agent)

Create default proxy configuration:

consul config write acls/proxy-default.hcl
  1. Start Nomad In a new terminal window, navigate to the quickstart directory again, and start Nomad in dev mode
sudo nomad agent -dev -dev-connect -config ./secrets/nomad-agent.hcl
  1. Configure Nomad CLI. Go back to the previous terminal window, and set your environment to configure the Nomad CLI to talk to the Nomad agent. Note that this command is surrounded by $(...) to run in a subshell to export the environment correctly.
$(make nomad-env)
  1. Bootstrap Nomad ACLs
nomad acl bootstrap ./secrets/tokens/nomad-root
  1. Configure Nomad and Consul to use Workload Identity. This will create a Consul auth method and binding rule that Nomad can use to get Consul tokens for Nomad workloads.
nomad setup consul -y \
    -jwks-url "$NOMAD_ADDR/.well-known/jwks.json" \
    -jwks-ca-file "$NOMAD_CACERT"
  1. Verify Nomad connectivity to Consul. Checking the node status should show it has fingerprinted attributes for Consul
nomad node status -verbose -self | grep consul

If you've skipped this section because you already have a Nomad and Consul cluster with Workload Identity configured, you should ensure your terminal is configured with environment variables to connect to both the Consul and Nomad APIs, and that you have a management token for both. Typically this should include all the following variables:

CONSUL_CACERT
CONSUL_CLIENT_CERT
CONSUL_CLIENT_KEY
CONSUL_HTTP_ADDR
CONSUL_HTTP_TOKEN

NOMAD_CACERT
NOMAD_CLIENT_CERT
NOMAD_CLIENT_KEY
NOMAD_ADDR
NOMAD_TOKEN

Return to the root of the repository if you haven't already.

Create required policies

Create a Nomad namespace:

nomad namespace apply \
    -description "namespace for Consul API Gateways" \
    ingress

Create a Consul policy for the API Gateway and a role with access to that policy. Note that the name of the role must match the binding rule nomad-${value.nomad_namespace}-tasks that you have previously set up for using Nomad Workload Identity with Consul, when used with the ingress namespace you just created.

consul acl policy create -name "api-gateways" \
    -description "api gateway policy" \
    -rules @acls/api-gateway.policy.hcl

consul acl role create \
       -name "nomad-ingress-tasks" \
       -description "role for Nomad API gateway workloads" \
       -policy-name "api-gateways"

Upload certificates for API Gateway

The API Gateway job needs Consul mTLS certificates to communicate with Consul. The job specification uses Nomad Variables to store these securely, but you could also use Vault secrets. These variables need to be written to the same namespace that the job will be deployed to.

nomad var put -namespace ingress \
    nomad/jobs/ingress/gateway/setup \
    consul_cacert=@$CONSUL_CACERT \
    consul_client_cert=@$CONSUL_CLIENT_CERT \
    consul_client_key=@$CONSUL_CLIENT_KEY

Deploy API Gateway

Look at the api-gateway.nomad.hcl job specification file at the root of this repository. Edit the main listener port network.port.http.static so that it's listening on whichever port you'd like.

Run the Nomad job.

nomad job run ./api-gateway.nomad.hcl

If you have specific Docker images or Nomad namespace you'd like to use, pass the -var option to the nomad job run command. For example:

nomad job run \
    -var="consul_image=hashicorp/consul:1.18.1 \
    -var="envoy_image=hashicorp/envoy:1.28.1 \
    -var="namespace=consul"

Once the deployment is complete, you can check the Consul UI to see the API Gateway registered.

Run an example upstream

This section will run an example upstream application hello and configure access to it from the API Gateway.

  1. Add intentions to allow traffic from the API Gateway to hello by running consul config write example/hello-app-intentions.hcl

  2. Register a listener for the API Gateway by running consul config write example/gateway-listeners.hcl

  3. Register http routes for the API Gateway so that Envoy knows how and where to write the traffic by running consul config write example/my-http-route.hcl

  4. Start the hello app by running nomad run example/hello-app.nomad.hcl

Once the deployment is complete, you can test the API Gateway.

  • Run nomad job status -namespace ingress ingress to find the allocation for the API gateway.
  • Run nomad alloc -namespace ingress status :allocID to find the address for that allocation.
  • Run curl -v http://<api-gateway-address>:<api-gateway-port>/hello
  • You should see the response from hello-app.

For additional debugging, you can dive into Envoy configs through the Envoy admin url and nomad alloc exec, Nomad job logs and Consul catalog service definition.