Consul integration

Consul integration

Consul is a widely used service mesh. Emissary natively supports service discovery and unauthenticated communication to services in Consul. Additionally, the Ambassador Consul Connector enables Emissary to encrypt and authenticate its communication via mTLS with services in Consul that make use of Consul’s Connect feature.

Architecture overview

Using Consul with Emissary is particularly useful when deploying Emissary in hybrid cloud environments where you deploy applications on VMs and Kubernetes. In this environment, Consul enables Emissary to securely route over TLS to any application regardless of where it is deployed.

In this architecture, Consul serves as the source of truth for your entire data center, tracking available endpoints, service configuration, and secrets for TLS encryption. New applications and services automatically register themselves with Consul using the Consul agent or API. When you send a request through Emissary, Emissary sends the request to an endpoint based on the data in Consul.

ambassador-consul

This guide first instructs you on registering a service with Consul and using Emissary to dynamically route requests to that service based on Consul’s service discovery data, and subsequently instructs you on using using the Ambassador Consul Connector to use Consul for authorizing and encrypting requests.

Installing Consul

If you already have Consul installed in your cluster, then go ahead and skip to the next section.

Before you install Consul, make sure to check the Consul documentation for any setup steps specific to your platform. Below you can find setup guides for some of the more popular Kubernetes platforms. This step is primarily to ensure you have the proper permissions to set up Consul. You can skip these guides if your cluster is already configured to grant you the necessary permissions.
If you did not find your Kubernetes platform above, check the Consul documentation here to see if there are specific setup instructions for your platform.
Add the Hashicorp repository for installing Consul with Helm. If you do not have Helm installed, you can find an installation guide here.
```
helm repo add hashicorp https://helm.releases.hashicorp.com
```
Create a new consul-values.yaml YAML file for the Consul installation values and copy the values below into that file.
```
global:
  datacenter: dc1

ui:
  service:
    type: 'LoadBalancer'

syncCatalog:
  enabled: true

server:
  replicas: 1
  bootstrapExpect: 1

connectInject:
  enabled: true
```
Note: you are free to change the value of the datacenter field in the install values. This is the the name of your Consul Datacenter.
Install Consul with Helm using the consul-values.yaml values file you just created.
```
helm install -f consul-values.yaml hashicorp hashicorp/consul
```

Installing Emissary

If you have not already installed Emissary in to your cluster, then go to the quick start guide before continuing any further in this guide.

Using Consul for service discovery

This section of the guide instructs you on configuring Emissary to look for services registered to Consul, registering a demo application with Consul, and configuring Emissary to route to this application using endpoint data from Consul.

In this tutorial, you deploy the application in Kubernetes. However, this application can be deployed anywhere in your data center, such as on a VM.

Configure Emissary to look for services registered to Consul by creating the ConsulResolver. Use kubectl to apply the following manifest:
```
kubectl apply -f <<EOF
---
apiVersion: getambassador.io/v3alpha1
kind: ConsulResolver
metadata:
  name: consul-dc1
spec:
  address: http://hashicorp-consul-server-0.hashicorp-consul-server.default.svc.cluster.local:8500
  datacenter: dc1
EOF
```
Note: If you changed the name of your datacenter in the Consul install values, make sure to change it in the resolver above to match the name of your datacenter.

If you changed the name of the helm install from hashicorp to another value, make sure to update the value of the address field in your resolver to match it.

If you are having trouble figuring out what your address field should be, it follow this format: http://{consul_server_pod}.{consul_server_service}.{namespace}.svc.cluster.local:{consul_port}. The default Consul port should be 8500 unless you changed it.

This tells Emissary that Consul is a service discovery endpoint.

You must set the resolver to your ConsulResolver on a per-Mapping basis, otherwise for that Mapping Emissary uses the default resolver. That is, in order for a Mapping to make use of a service registered in Consul, you need to add resolver: consul-dc1 to that Mapping.

For more information about resolver configuration, see the resolver reference documentation. (If you’re using Consul deployed elsewhere in your data center, make sure the address points to your Consul FQDN or IP address).

Deploy the Quote demo application. Use kubectl to apply the following manifest:

kubectl apply -f <<EOF
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: quote-consul
spec:
  replicas: 1
  strategy:
    type: RollingUpdate
  selector:
    matchLabels:
      app: quote-consul
  template:
    metadata:
      labels:
        app: quote-consul
      annotations:
        "consul.hashicorp.com/connect-inject": "false"
    spec:
      containers:
      - name: backend
        image: docker.io/datawire/quote:$quoteVersion$
        ports:
        - name: http
          containerPort: 8080
        env:
        - name: CONSUL_IP
          valueFrom:
            fieldRef:
              fieldPath: status.hostIP
        - name: POD_IP
          valueFrom:
            fieldRef:
              fieldPath: status.podIP
        - name: SERVICE_NAME
          value: "quote-consul"
        readinessProbe:
          httpGet:
            path: /health
            port: 8080
          initialDelaySeconds: 30
          periodSeconds: 3
        resources:
          limits:
            cpu: "0.1"
            memory: 100Mi
EOF

The SERVICE_NAME environment variable in the quote-consul Deployment specifies the service name for Consul. The default value is set to “quote-consul”, so you only need to include it if you want to change the service name.

The Quote application contains code to automatically register itself with Consul, using the CONSUL_IP and POD_IP environment variables specified within the quote-consul container spec.

When you apply this manifest, it registers the Pod in the quote-consul Deployment as a Consul service with the name quote-consul and the IP address of the Pod.

The "consul.hashicorp.com/connect-inject": "false" annotation tells Consul that for this Deployment you do not want to use the sidecar proxy that is part of Consul’s Connect feature. Without Consul’s sidecar, the service needs to include code to make a request to Consul to register the service. The manifest includes the environment variables CONSUL_IP, POD_IP, and SERVICE_NAME to provide the Quote service with enough information to build that request and send it to Consul. To see how this code works, see our our Git repo for the Quote service.

Verify the quote-consul Deployment’s Pod has been registered with Consul. You can verify this by accessing the Consul UI.

First use kubectl port-forward to make the UI available on your local workstation:
```
kubectl port-forward service/hashicorp-consul-ui 8500:80
```
Then, while the port-forward is running, go to http://localhost:8500/ in a web browser. You should see a service named quote-consul.

After you have verified that you see the quote-consul service in your web browser, you may kill the port-forward.

Port forwarding not working for you? Make sure the service name matches your Consul UI service by checking kubectl get svc -A
Configure Emissary to make use of this quote-consul service. Use kubectl to apply the following manifest:
```
kubectl apply -f <<EOF
---
apiVersion: getambassador.io/v3alpha1
kind: Mapping
metadata:
  name: consul-quote-mapping
spec:
  hostname: "*"
  prefix: /quote-consul/
  service: quote-consul
  resolver: consul-dc1
  load_balancer:
    policy: round_robin
EOF
```
Note that in the above config:
- service refers to the service name you specified in the quote-consul Deployment.
- resolver must be set to the ConsulResolver that you created in the previous step.
- load_balancer must be set to configure Emissary to route directly to the Quote application endpoints that are retrieved from Consul.

Send a request to the /quote-consul/ API endpoint in order to validate that Emissary is now making use of that service:

$ AMBASSADOR_IP=$(kubectl --namespace $productNamespace$ get services/$productDeploymentName$ -o "go-template={{range .status.loadBalancer.ingress}}{{or .ip .hostname}}{{end}}")
$ curl -Lk http://$AMBASSADOR_IP/quote-consul/
{
 "server": "janky-elderberry-vtqtolsz",
 "quote": "The last sentence you read is often sensible nonsense.",
 "time": "2021-03-24T23:33:08.515530972Z"
}

Congratulations! You’re successfully routing traffic to the Quote application, the location of which is registered in Consul.

Using Consul for authorization and encryption

In this part of the guide, you’ll install a different version of the demo application that now uses Consul’s Connect feature to authorize its incoming connections using mTLS, and install Ambassador Consul Connector to enable Emissary to authenticate to such services.

The following steps assume you’ve already set up Consul for service discovery, as detailed above.

The Ambassador Consul Connector retrieves the TLS certificate issued by the Consul CA and stores it in a Kubernetes Secret for Emissary to use. Deploy the Ambassador Consul Connector with kubectl:
```
kubectl apply -f https://app.getambassador.io/yaml/v2-docs/$ossVersion$/consul/ambassador-consul-connector.yaml
```
This installs in to your cluster:
- RBAC resources.
- The Ambassador Consul Connector service.
- A TLSContext named ambassador-consul to load the ambassador-consul-connect Secret into Emissary.

Deploy a new version of the demo application, and configure it to inject the Consul Connect sidecar by setting "consul.hashicorp.com/connect-inject" to true. Note that in this version of the configuration, you do not have to configure environment variables for the location of the Consul server. Use kubectl to apply the following manifest:

kubectl apply -f - <<EOF
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: quote-connect
spec:
  replicas: 1
  strategy:
    type: RollingUpdate
  selector:
    matchLabels:
      app: quote-connect
  template:
    metadata:
      labels:
        app: quote-connect
      annotations:
        "consul.hashicorp.com/connect-inject": "true"
    spec:
      containers:
      - name: quote
        image: docker.io/datawire/quote:$quoteVersion$
        ports:
        - name: http
          containerPort: 8080
        readinessProbe:
          httpGet:
            path: /health
            port: 8080
          initialDelaySeconds: 30
          periodSeconds: 3
        resources:
          limits:
            cpu: "0.1"
            memory: 100Mi
---
apiVersion: v1
kind: Service
metadata:
  name: quote-connect
  annotations:
    a8r.io/description: "Quote service"
    a8r.io/owner: "No owner"
    a8r.io/chat: "#ambassador"
    a8r.io/bugs: "https://github.com/datawire/quote/issues"
    a8r.io/documentation: "https://github.com/datawire/quote/blob/master/README.md"
    a8r.io/repository: "https://github.com/datawire/quote"
    a8r.io/support: "http://a8r.io/Slack"
    a8r.io/runbook: "https://github.com/datawire/quote/blob/master/README.md"
    a8r.io/incidents: "https://github.com/datawire/quote/issues"
    a8r.io/dependencies: "None"
spec:
  ports:
  - name: http
    port: 80
    targetPort: 8080
  selector:
    app: quote-connect
EOF

Note: Annotations are used to attach metadata to Kubernetes objects. You can use annotations to link external information to objects, working in a similar, yet different, fashion to labels. For more information on annotations, refer to the Annotating Kubernetes Services for Humans article, or get started with annotations in your own cluster with the Ambassador Cloud Quick start guide.

This deploys a demo application Deployment called quote-connect (different than the quote-consul Deployment in the previous section) with the Consul Connect sidecar proxy. The Connect sidecar registers the application with Consul, requires TLS to access the application, and exposes other Consul Service Segmentation features.

The annotation consul.hashicorp.com/connect-inject being set to true in this Deployment tells Consul that you want this Deployment to use the Consul Connect sidecar. The sidecar proxies requests to the service that it is attached to. Keep this in mind mind when debug requests to the service.

Verify the quote-connect Deployment’s Pod has been registered with Consul. You can verify this by accessing the Consul UI.

First use kubectl port-forward to make the UI available on your local workstation:
```
kubectl port-forward service/hashicorp-consul-ui 8500:80
```
Then, while the port-forward is running, open http://localhost:8500/ in a web browser. You should see a service named quote-connect.

After you have verified that you see the quote-connect service in your web browser, you may kill the port-forward.
Create a Mapping to configure Emissary route to the quote-connect service in Consul. Use kubectl to apply the following manifest:
```
kubectl apply -f <<EOF
---
apiVersion: getambassador.io/v3alpha1
kind: Mapping
metadata:
  name: quote-connect-mapping
spec:
  hostname: "*"
  prefix: /quote-connect/
  service: quote-connect-sidecar-proxy
  resolver: consul-dc1
  tls: ambassador-consul
  load_balancer:
    policy: round_robin
EOF
```
Note that in the above config:
- service must be set to the name of the Consul sidecar service. You can view this with kubectl get svc -A it should follow the format of {service name}-sidecar-proxy.
- resolver must be set to the ConsulResolver created when configuring Emissary.
- tls must be set to the TLSContext storing the Consul mTLS certificates, which is ambassador-consul in the standard ambassador-consul-connector.yaml.
- load_balancer must be set to configure Emissary to route directly to the application endpoints that are retrieved from Consul.
When you apply this manifest, it creates a Mapping that routes to the quote-connect service in Consul.

Send a request to the /quote-connect/ API endpoint in order to validate that Emissary is now using mTLS to encrypt and authenticate communication with that service:

$ AMBASSADOR_IP=$(kubectl --namespace $productNamespace$ get services/$productDeploymentName$ -o "go-template={{range .status.loadBalancer.ingress}}{{or .ip .hostname}}{{end}}")
$ curl -Lk http://$AMBASSADOR_IP/quote-connect/
{
 "server": "tasty-banana-2h6qpwme",
 "quote": "Nihilism gambles with lives, happiness, and even destiny itself!",
 "time": "2021-03-24T23:31:58.47597266Z"
}

Congratulations! You successfully configured the service to work with the Consul Connect sidecar.

Environment variables

The Ambassador Consul Connector can be configured with the following environment variables. The defaults are best for most use-cases.

Environment Variable	Description	Default
`_AMBASSADOR_ID`	Set the Ambassador ID so multiple instances of this integration can run per-Cluster when there are multiple $productNamePlural$ (Required if `AMBASSADOR_ID` is set in your Emissary `Deployment`)	`""`
`_CONSUL_HOST`	Set the IP or DNS name of the target Consul HTTP API server	`127.0.0.1`
`_CONSUL_PORT`	Set the port number of the target Consul HTTP API server	`8500`
`_AMBASSADOR_TLS_SECRET_NAME`	Set the name of the Kubernetes `v1.Secret` created by this program that contains the Consul-generated TLS certificate.	`$AMBASSADOR_ID-consul-connect`
`_AMBASSADOR_TLS_SECRET_NAMESPACE`	Set the namespace of the Kubernetes `v1.Secret` created by this program.	(same Namespace as the Pod running this integration)

More information

For more about Emissary’s integration with Consul, read the service discovery configuration documentation.

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Last modified August 3, 2024: Update all 3.6 resources with appropriate metadata (2d36673)