Mesh Expansion

8 minute read

This guide provides instructions to integrate VMs and bare metal hosts into an Istio mesh deployed on Kubernetes.

Prerequisites

You have already set up Istio on Kubernetes. If you haven’t done so, you can find out how in the Installation guide.
Mesh expansion machines must have IP connectivity to the endpoints in the mesh. This typically requires a VPC or a VPN, as well as a container network that provides direct (without NAT or firewall deny) routing to the endpoints. The machine is not required to have access to the cluster IP addresses assigned by Kubernetes.
Mesh expansion VMs must have access to a DNS server that resolves names to cluster IP addresses. Options include exposing the Kubernetes DNS server through an internal load balancer, using a Core DNS server, or configuring the IPs in any other DNS server accessible from the VM.
Install the Helm client. Helm is needed to enable mesh expansion.

The following instructions:

Assume the expansion VM is running on GCE.
Use Google platform-specific commands for some steps.

Installation steps

Setup consists of preparing the mesh for expansion and installing and configuring each VM.

Preparing the Kubernetes cluster for expansion

The first step when adding non-Kubernetes services to an Istio mesh is to configure the Istio installation itself, and generate the configuration files that let mesh expansion VMs connect to the mesh. To prepare the cluster for mesh expansion, run the following commands on a machine with cluster admin privileges:

Ensure that mesh expansion is enabled for the cluster. If you didn’t use the --set global.meshExpansion.enabled=true flag when installing Helm, you can use one of the following two options depending on how you originally installed Istio on the cluster:
- If you installed Istio with Helm and Tiller, run helm upgrade with the new option:
```
$ cd install/kubernetes/helm/istio
$ helm upgrade --set global.meshExpansion.enabled=true istio .
$ cd -
```
- If you installed Istio without Helm and Tiller, use helm template to update your configuration with the option and reapply with kubectl:
```
$ kubectl create namespace istio-system
$ helm template  install/kubernetes/helm/istio-init --name istio-init --namespace istio-system  | kubectl apply -f -
$ cd install/kubernetes/helm/istio
$ helm template --set global.meshExpansion.enabled=true --namespace istio-system . > istio.yaml
$ kubectl apply -f istio.yaml
$ cd -
```
When updating configuration with Helm, you can either set the option on the command line, as in our examples, or add it to a .yaml values file and pass it to the command with --values, which is the recommended approach when managing configurations with multiple options. You can see some sample values files in your Istio installation’s install/kubernetes/helm/istio directory and find out more about customizing Helm charts in the Helm documentation.
Define the namespace the VM joins. This example uses the SERVICE_NAMESPACE environment variable to store the namespace. The value of this variable must match the namespace you use in the configuration files later on.
```
$ export SERVICE_NAMESPACE="default"
```

Determine and store the IP address of the Istio ingress gateway since the mesh expansion machines access Citadel and Pilot through this IP address.

$ export GWIP=$(kubectl get -n istio-system service istio-ingressgateway -o jsonpath='{.status.loadBalancer.ingress[0].ip}')
$ echo $GWIP
35.232.112.158

Generate a cluster.env configuration to deploy in the VMs. This file contains the Kubernetes cluster IP address ranges to intercept and redirect via Envoy. You specify the CIDR range when you install Kubernetes as servicesIpv4Cidr. Replace $MY_ZONE and $MY_PROJECT in the following example commands with the appropriate values to obtain the CIDR after installation:
```
$ ISTIO_SERVICE_CIDR=$(gcloud container clusters describe $K8S_CLUSTER --zone $MY_ZONE --project $MY_PROJECT --format "value(servicesIpv4Cidr)")
$ echo -e "ISTIO_CP_AUTH=MUTUAL_TLS\nISTIO_SERVICE_CIDR=$ISTIO_SERVICE_CIDR\n" > cluster.env
```
Check the contents of the generated cluster.env file. It should be similar to the following example:
```
$ cat cluster.env
ISTIO_CP_AUTH=MUTUAL_TLS
ISTIO_SERVICE_CIDR=10.55.240.0/20
```
If the VM only calls services in the mesh, you can skip this step. Otherwise, add the ports the VM exposes to the cluster.env file with the following command. You can change the ports later if necessary.
```
$ echo "ISTIO_INBOUND_PORTS=3306,8080" >> cluster.env
```

Extract the initial keys the service account needs to use on the VMs.

$ kubectl -n $SERVICE_NAMESPACE get secret istio.default  \
    -o jsonpath='{.data.root-cert\.pem}' |base64 --decode > root-cert.pem
$ kubectl -n $SERVICE_NAMESPACE get secret istio.default  \
    -o jsonpath='{.data.key\.pem}' |base64 --decode > key.pem
$ kubectl -n $SERVICE_NAMESPACE get secret istio.default  \
      -o jsonpath='{.data.cert-chain\.pem}' |base64 --decode > cert-chain.pem

Setting up the VM

Next, run the following commands on each machine that you want to add to the mesh:

Copy the previously created cluster.env and *.pem files to the VM. For example:

$ export GCE_NAME="your-gce-instance"
$ gcloud compute scp --project=${MY_PROJECT} --zone=${MY_ZONE} {key.pem,cert-chain.pem,cluster.env,root-cert.pem} ${GCE_NAME}:~

Install the Debian package with the Envoy sidecar.

$ gcloud compute ssh --project=${MY_PROJECT} --zone=${MY_ZONE} "${GCE_NAME}"
$ curl -L https://storage.googleapis.com/istio-release/releases/1.2.5/deb/istio-sidecar.deb > istio-sidecar.deb
$ sudo dpkg -i istio-sidecar.deb

Add the IP address of the Istio gateway to /etc/hosts. Revisit the preparing the cluster section to learn how to obtain the IP address. The following example updates the /etc/hosts file with the Istio gateway address:
```
$ echo "35.232.112.158 istio-citadel istio-pilot istio-pilot.istio-system" | sudo tee -a /etc/hosts
```

Install root-cert.pem, key.pem and cert-chain.pem under /etc/certs/.

$ sudo mkdir -p /etc/certs
$ sudo cp {root-cert.pem,cert-chain.pem,key.pem} /etc/certs

Install cluster.env under /var/lib/istio/envoy/.
```
$ sudo cp cluster.env /var/lib/istio/envoy
```
Transfer ownership of the files in /etc/certs/ and /var/lib/istio/envoy/ to the Istio proxy.
```
$ sudo chown -R istio-proxy /etc/certs /var/lib/istio/envoy
```

Verify the node agent works:

$ sudo node_agent
....
CSR is approved successfully. Will renew cert in 1079h59m59.84568493s

Start Istio using systemctl.

$ sudo systemctl start istio-auth-node-agent
$ sudo systemctl start istio

Send requests from VM workloads to Kubernetes services

After setup, the machine can access services running in the Kubernetes cluster or on other mesh expansion machines.

The following example shows accessing a service running in the Kubernetes cluster from a mesh expansion VM using /etc/hosts/, in this case using a service from the Bookinfo example.

First, on the cluster admin machine get the virtual IP address (clusterIP) for the service:
```
$ kubectl get svc productpage -o jsonpath='{.spec.clusterIP}'
10.55.246.247
```

Then on the mesh expansion machine, add the service name and address to its etc/hosts file. You can then connect to the cluster service from the VM, as in the example below:

$ echo "10.55.246.247 productpage.default.svc.cluster.local" | sudo tee -a /etc/hosts
$ curl -v productpage.default.svc.cluster.local:9080
< HTTP/1.1 200 OK
< content-type: text/html; charset=utf-8
< content-length: 1836
< server: envoy
... html content ...

The server: envoy header indicates that the sidecar intercepted the traffic.

Running services on a mesh expansion machine

Setup an HTTP server on the VM instance to serve HTTP traffic on port 8080:
```
$ gcloud compute ssh ${GCE_NAME}
$ python -m SimpleHTTPServer 8080
```

Determine the VM instance’s IP address. For example, find the IP address of the GCE instance with the following commands:

$ export GCE_IP=$(gcloud --format="value(networkInterfaces[0].networkIP)" compute instances describe ${GCE_NAME})
$ echo ${GCE_IP}

Configure a service entry to enable service discovery for the VM. You can add VM services to the mesh using a service entry. Service entries let you manually add additional services to Pilot’s abstract model of the mesh. Once VM services are part of the mesh’s abstract model, other services can find and direct traffic to them. Each service entry configuration contains the IP addresses, ports, and appropriate labels of all VMs exposing a particular service, for example:
```
$ kubectl -n ${SERVICE_NAMESPACE} apply -f - <<EOF
apiVersion: networking.istio.io/v1alpha3
kind: ServiceEntry
metadata:
  name: vmhttp
spec:
  hosts:
  - vmhttp.${SERVICE_NAMESPACE}.svc.cluster.local
  ports:
  - number: 8080
    name: http
    protocol: HTTP
  resolution: STATIC
  endpoints:
  - address: ${GCE_IP}
    ports:
      http: 8080
    labels:
      app: vmhttp
      version: "v1"
EOF
```
The workloads in a Kubernetes cluster need a DNS mapping to resolve the domain names of VM services. To integrate the mapping with your own DNS system, use istioctl register and creates a Kubernetes selector-less service, for example:
```
$ istioctl  register -n ${SERVICE_NAMESPACE} vmhttp ${GCE_IP} 8080
```
Make sure you have already added istioctl client to your PATH environment variable, as described in the Download page.

Deploy a pod running the sleep service in the Kubernetes cluster, and wait until it is ready:

$ kubectl apply -f @samples/sleep/sleep.yaml@
$ kubectl get pod
NAME                             READY     STATUS    RESTARTS   AGE
productpage-v1-8fcdcb496-xgkwg   2/2       Running   0          1d
sleep-88ddbcfdd-rm42k            2/2       Running   0          1s
...

Send a request from the sleep service on the pod to the VM’s HTTP service:

$ kubectl exec -it sleep-88ddbcfdd-rm42k -c sleep -- curl vmhttp.${SERVICE_NAMESPACE}.svc.cluster.local:8080

You should see something similar to the output below.

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><html>
<title>Directory listing for /</title>
<body>
<h2>Directory listing for /</h2>
<hr>
<ul>
<li><a href=".bashrc">.bashrc</a></li>
<li><a href=".ssh/">.ssh/</a></li>
...
</body>

Congratulations! You successfully configured a service running in a pod within the cluster to send traffic to a service running on a VM outside of the cluster and tested that the configuration worked.

Cleanup

Run the following commands to remove the expansion VM from the mesh’s abstract model.

$ istioctl deregister -n ${SERVICE_NAMESPACE} vmhttp ${GCE_IP}
2019-02-21T22:12:22.023775Z     info    Deregistered service successfull
$ kubectl delete ServiceEntry vmhttp -n ${SERVICE_NAMESPACE}
serviceentry.networking.istio.io "vmhttp" deleted

Troubleshooting

The following are some basic troubleshooting steps for common mesh expansion issues.

When making requests from a VM to the cluster, ensure you don’t run the requests as root or istio-proxy user. By default, Istio excludes both users from interception.
Verify the machine can reach the IP of the all workloads running in the cluster. For example:

$ kubectl get endpoints productpage -o jsonpath='{.subsets[0].addresses[0].ip}'
10.52.39.13

$ curl 10.52.39.13:9080
html output

Check the status of the node agent and sidecar:

$ sudo systemctl status istio-auth-node-agent
$ sudo systemctl status istio

Check that the processes are running. The following is an example of the processes you should see on the VM if you run ps, filtered for istio:

$ ps aux | grep istio
root      6941  0.0  0.2  75392 16820 ?        Ssl  21:32   0:00 /usr/local/istio/bin/node_agent --logtostderr
root      6955  0.0  0.0  49344  3048 ?        Ss   21:32   0:00 su -s /bin/bash -c INSTANCE_IP=10.150.0.5 POD_NAME=demo-vm-1 POD_NAMESPACE=default exec /usr/local/bin/pilot-agent proxy > /var/log/istio/istio.log istio-proxy
istio-p+  7016  0.0  0.1 215172 12096 ?        Ssl  21:32   0:00 /usr/local/bin/pilot-agent proxy
istio-p+  7094  4.0  0.3  69540 24800 ?        Sl   21:32   0:37 /usr/local/bin/envoy -c /etc/istio/proxy/envoy-rev1.json --restart-epoch 1 --drain-time-s 2 --parent-shutdown-time-s 3 --service-cluster istio-proxy --service-node sidecar~10.150.0.5~demo-vm-1.default~default.svc.cluster.local

Check the Envoy access and error logs:

$ tail /var/log/istio/istio.log
$ tail /var/log/istio/istio.err.log