Kubernetes service mesh workload scenarios

This page provides example workflows for registering workloads on Kubernetes into Consul's service mesh in different scenarios, including multiport deployments. Each scenario provides an example Kubernetes manifest to demonstrate how to use Consul's service mesh with a specific Kubernetes workload type.

Kubernetes Pods running as a deployment

The following example shows a Kubernetes configuration that specifically enables service mesh connections for the static-server service. Consul starts and registers a sidecar proxy that listens on port 20000 by default and proxies valid inbound connections to port 8080.

apiVersion: v1
kind: Service
metadata:
  # This name will be the service name in Consul.
  name: static-server
spec:
  selector:
    app: static-server
  ports:
    - protocol: TCP
      port: 80
      targetPort: 8080
---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: static-server
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: static-server
spec:
  replicas: 1
  selector:
    matchLabels:
      app: static-server
  template:
    metadata:
      name: static-server
      labels:
        app: static-server
      annotations:
        'consul.hashicorp.com/connect-inject': 'true'
    spec:
      containers:
        - name: static-server
          image: hashicorp/http-echo:latest
          args:
            - -text="hello world"
            - -listen=:8080
          ports:
            - containerPort: 8080
              name: http
      # If ACLs are enabled, the serviceAccountName must match the Consul service name.
      serviceAccountName: static-server

To establish a connection to the upstream Pod using service mesh, a client must dial the upstream workload using a mesh proxy. The client mesh proxy will use Consul service discovery to find all available upstream proxies and their public ports.

Connecting to mesh-enabled Services

The example Deployment specification below configures a Deployment that is capable of establishing connections to our previous example "static-server" service. The connection to this static text service happens over an authorized and encrypted connection via service mesh.

apiVersion: v1
kind: Service
metadata:
  # This name will be the service name in Consul.
  name: static-client
spec:
  selector:
    app: static-client
  ports:
    - port: 80
---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: static-client
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: static-client
spec:
  replicas: 1
  selector:
    matchLabels:
      app: static-client
  template:
    metadata:
      name: static-client
      labels:
        app: static-client
      annotations:
        'consul.hashicorp.com/connect-inject': 'true'
    spec:
      containers:
        - name: static-client
          image: curlimages/curl:latest
          # Just spin & wait forever, we'll use `kubectl exec` to demo
          command: ['/bin/sh', '-c', '--']
          args: ['while true; do sleep 30; done;']
      # If ACLs are enabled, the serviceAccountName must match the Consul service name.
      serviceAccountName: static-client

By default when ACLs are enabled or when ACLs default policy is allow, Consul will automatically configure proxies with all upstreams from the same datacenter. When ACLs are enabled with default deny policy, you must supply an intention to tell Consul which upstream you need to talk to.

When upstreams are specified explicitly with the consul.hashicorp.com/connect-service-upstreams annotation, the injector will also set environment variables <NAME>_CONNECT_SERVICE_HOST and <NAME>_CONNECT_SERVICE_PORT in every container in the Pod for every defined upstream. This is analogous to the standard Kubernetes service environment variables, but point instead to the correct local proxy port to establish connections via service mesh.

You cannot reference auto-generated environment variables when the upstream annotation contains a dot. This is because Consul also renders the environment variables to include a dot. For example, Consul renders the variables generated for static-server.svc:8080 as STATIC-SERVER.SVC_CONNECT_SERVICE_HOST and STATIC_SERVER.SVC_CONNECT_SERVICE_PORT, which makes the variables unusable. You can verify access to the static text server using kubectl exec. Because transparent proxy is enabled by default, use Kubernetes DNS to connect to your desired upstream.

$ kubectl exec deploy/static-client -- curl --silent http://static-server/
"hello world"

You can control access to the server using intentions. If you use the Consul UI or CLI to deny communication between "static-client" and "static-server", connections are immediately rejected without updating either of the running pods. You can then remove this intention to allow connections again.

$ kubectl exec deploy/static-client -- curl --silent http://static-server/
command terminated with exit code 52

Kubernetes Jobs

Kubernetes Jobs run pods that only make outbound requests to services on the mesh and successfully terminate when they are complete. In order to register a Kubernetes Job with the mesh, you must provide an integer value for the consul.hashicorp.com/sidecar-proxy-lifecycle-shutdown-grace-period-seconds annotation. Then, issue a request to the http://127.0.0.1:20600/graceful_shutdown API endpoint so that Kubernetes gracefully shuts down the consul-dataplane sidecar after the job is complete.

Below is an example Kubernetes manifest that deploys a job correctly.

---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: test-job
  namespace: default
---
apiVersion: v1
kind: Service
metadata:
  name: test-job
  namespace: default
spec:
  selector:
    app: test-job
  ports:
    - port: 80
---
apiVersion: batch/v1
kind: Job
metadata:
   name: test-job
   namespace: default
   labels:
     app: test-job
spec:
  template:
    metadata:
      annotations:
        'consul.hashicorp.com/connect-inject': 'true'
        'consul.hashicorp.com/sidecar-proxy-lifecycle-shutdown-grace-period-seconds': '5'
      labels:
        app: test-job
    spec:
      containers:
      - name: test-job
        image: alpine/curl:3.14
        ports:
        - containerPort: 80
        command:
          - /bin/sh
          - -c
          - |
            echo "Started test job"
            sleep 10
            echo "Killing proxy"
            curl --max-time 2 -s -f -X POST http://127.0.0.1:20600/graceful_shutdown
            sleep 10
            echo "Ended test job"
      serviceAccountName: test-job
      restartPolicy: Never

Upon completing the job you should be able to verify that all containers are shut down within the pod.

$ kubectl get pods
NAME             READY   STATUS      RESTARTS   AGE
test-job-49st7   0/2     Completed   0          3m55s

$ kubectl get job
NAME       COMPLETIONS   DURATION   AGE
test-job   1/1           30s        4m31s

In addition, based on the logs emitted by the pod you can verify that the proxy was shut down before the Job completed.

$ kubectl logs test-job-49st7 -c test-job
Started test job
Killing proxy
Ended test job

Kubernetes Pods with multiple ports

To configure a pod with multiple ports to be a part of the service mesh and receive and send service mesh traffic, you will need to add configuration so that a Consul service can be registered per port. This is because services in Consul currently support a single port per service instance.

In the following example, suppose we have a pod which exposes 2 ports, 8080 and 9090, both of which will need to receive service mesh traffic.

First, decide on the names for the two Consul services that will correspond to those ports. In this example, the user chooses the names web for 8080 and web-admin for 9090.

Create two service accounts for web and web-admin:

apiVersion: v1
kind: ServiceAccount
metadata:
  name: web
---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: web-admin

Create two Service objects for web and web-admin:

apiVersion: v1
kind: Service
metadata:
  name: web
spec:
  selector:
    app: web
  ports:
    - protocol: TCP
      port: 80
      targetPort: 8080
---
apiVersion: v1
kind: Service
metadata:
  name: web-admin
spec:
  selector:
    app: web
  ports:
    - protocol: TCP
      port: 80
      targetPort: 9090

web will target containerPort 8080 and select pods labeled app: web. web-admin will target containerPort 9090 and will also select the same pods.

apiVersion: v1
kind: Secret
metadata:
  name: web
  annotations:
    kubernetes.io/service-account.name: web
type: kubernetes.io/service-account-token
---
apiVersion: v1
kind: Secret
metadata:
  name: web-admin
  annotations:
    kubernetes.io/service-account.name: web-admin
type: kubernetes.io/service-account-token

Create a Deployment with any chosen name, and use the following annotations:

annotations:
  'consul.hashicorp.com/connect-inject': 'true'
  'consul.hashicorp.com/transparent-proxy': 'false'
  'consul.hashicorp.com/connect-service': 'web,web-admin'
  'consul.hashicorp.com/connect-service-port': '8080,9090'

Note that the order the ports are listed in the same order as the service names, i.e. the first service name web corresponds to the first port, 8080, and the second service name web-admin corresponds to the second port, 9090.

The service account on the pod spec for the deployment should be set to the first service name web:

serviceAccountName: web

The following deployment example demonstrates the required annotations for the manifest. In addition, the previous YAML manifests can also be combined into a single manifest for easier deployment.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: web
spec:
  replicas: 1
  selector:
    matchLabels:
      app: web
  template:
    metadata:
      name: web
      labels:
        app: web
      annotations:
        'consul.hashicorp.com/connect-inject': 'true'
        'consul.hashicorp.com/transparent-proxy': 'false'
        'consul.hashicorp.com/connect-service': 'web,web-admin'
        'consul.hashicorp.com/connect-service-port': '8080,9090'
    spec:
      containers:
        - name: web
          image: hashicorp/http-echo:latest
          args:
            - -text="hello world"
            - -listen=:8080
          ports:
            - containerPort: 8080
              name: http
        - name: web-admin
          image: hashicorp/http-echo:latest
          args:
            - -text="hello world from 9090"
            - -listen=:9090
          ports:
            - containerPort: 9090
              name: http
      serviceAccountName: web

After deploying the web application, you can test service mesh connections by deploying the static-client application with the configuration in the previous section and add the consul.hashicorp.com/connect-service-upstreams: 'web:1234,web-admin:2234' annotation to the pod template on static-client:

apiVersion: v1
kind: Service
metadata:
  # This name will be the service name in Consul.
  name: static-client
spec:
  selector:
    app: static-client
  ports:
    - port: 80
---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: static-client
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: static-client
spec:
  replicas: 1
  selector:
    matchLabels:
      app: static-client
  template:
    metadata:
      name: static-client
      labels:
        app: static-client
      annotations:
        'consul.hashicorp.com/connect-inject': 'true'
        'consul.hashicorp.com/connect-service-upstreams': 'web:1234,web-admin:2234'
    spec:
      containers:
        - name: static-client
          image: curlimages/curl:latest
          # Just spin & wait forever, we'll use `kubectl exec` to demo
          command: ['/bin/sh', '-c', '--']
          args: ['while true; do sleep 30; done;']
      # If ACLs are enabled, the serviceAccountName must match the Consul service name.
      serviceAccountName: static-client

If you exec on to a static-client pod, using a command like:

$ kubectl exec -it static-client-5bd667fbd6-kk6xs -- /bin/sh

you can then run:

$ curl localhost:1234

to see the output hello world and run:

$ curl localhost:2234

to see the output hello world from 9090.

The way this works is that a Consul service instance is being registered per port on the Pod, so there are 2 Consul services in this case. An additional Envoy sidecar proxy and connect-init init container are also deployed per port in the Pod. So the upstream configuration can use the individual service names to reach each port as seen in the example.

Caveats for Multi-port Pods

• Transparent proxy is not supported for multi-port Pods.
• Metrics and metrics merging is not supported for multi-port Pods.
• Upstreams will only be set on the first service's Envoy sidecar proxy for the pod.
  • This means that ServiceIntentions from a multi-port pod to elsewhere, will need to use the first service's name, web in the example above to accept connections from either web or web-admin. ServiceIntentions from elsewhere to a multi-port pod can use the individual service names within the multi-port Pod.
• Health checking is done on a per-Pod basis, so if any Kubernetes health checks (like readiness, liveness, etc) are failing for any container on the Pod, the entire Pod is marked unhealthy, and any Consul service referencing that Pod will also be marked as unhealthy. So, if web has a failing health check, web-admin would also be marked as unhealthy for service mesh traffic.