Adding a Virtual Machine to the Mesh Using Calisti

Prasenjit Sarker
Prasenjit Sarker

Wednesday, May 25th, 2022

In a perfect world, every workload that you needed to deploy today would be designed from the ground up to be cloud native. It would run inside containers and play nicely with Kubernetes by default.

But the reality is that not all apps do these things. Many businesses need to deploy legacy workloads – such as virtual machines – within cloud native environments. This alone is very complicated. Add to this the fact that many businesses don’t have the time or resources to rebuild those workloads from scratch to fit cloud native security architecture.

As we explained in a previous blog, Calisti - The Cisco Service Mesh Manager addresses this challenge by making it easy to integrate VMs into a Istio Service Mesh. Calisti, which is built on top of Istio, treats VMs and containers alike as first-class citizens, which means you don’t need to cut corners or perform extra work to get legacy workloads running in a cloud native environment.

To prove the point, let’s walk step-by-step through the process of adding a virtual machine to your Istio Service Mesh using Calisti.

Step 0: Prerequisites for an Istio-based service mesh environment

For the purposes of this tutorial, you’ll need:

  • A VM that is configured to match the parameters described here.
    • In particular, you’ll need a Linux-based OS that supports Debian packages and systems, as well as access to TCP port 16400.
  • Root access to your VM.

VM

Step 1: Scale down analytics service from demo app

Note: If you are not using the demo application to test VM integration, skip this step. You can install the demo application on your Calisti cluster by running

smm demoapp install

Before proceeding further, we want to make sure there are no replicas for the analytics service running in your cluster. So, scale down to zero replicas with:

kubectl scale deploy -n smm-demo analytics-v1 --replicas=0

Verify that there are no replicas by running:

kubectl get pods -n smm-demo | grep analytics

This command should return nothing if you’ve successfully scaled down the analytics service.

Step 2: Configure an external workload

Calisti treats VMs as Kubernetes workloads. To connect a legacy VM to the service mesh, you need to assign a set of labels that match the machine.

Do that by using YAML, such as the following:

apiVersion: networking.istio.io/v1alpha3
  kind: WorkloadGroup
  metadata:
	labels:
  	app: analytics
  	version: v0
	name: analytics-v0
	namespace: smm-demo
  spec:
	metadata:
  	labels:
    	app: analytics
    	version: v0
	probe:
  	httpGet:
    	path: /
    	host: 127.0.0.1
    	port: 8080
    	scheme: HTTP
	template:
  	network: vm-network-1
  	ports:
    	http: 8080
    	grpc: 8082
    	tcp: 8083
  	serviceAccount: default

This adds a virtual machine serving the analytics traffic in the demo application.

Step 3: Optionally configure mTLS

If you need to configure communication without encryption on some service ports, you can do this by creating a PeerAuthentication object in the smm-demo namespace. For example:

apiVersion: security.istio.io/v1beta1
kind: PeerAuthentication
metadata:
  name: analytics
  namespace: smm-demo
spec:
  mtls:
	mode: PERMISSIVE
  selector:
	matchLabels:
  	app: analytics
  	version: v0

Note: You can skip this step if the default Istio Service Mesh networking settings suffice for your workload.

Step 4: Set up the VM

At this point, it’s time to start up the workload on your VM. Do this by logging into the VM and running whichever command starts the workload:

sudo /path/to/your_workload

You’ll also need iptables and curl installed on the VM. So, since you’re logged in anyway, go ahead and install them (if they’re not already installed) with:

sudo apt-get update && apt-get install -y curl iptables

Step 5: Collect credentials

To connect the VM to Istio service Mesh, you need to know the URL of the dashboard, the namespace and name of the WorkloadGroup and the bearer token of the service account referenced in the .spec.template.serviceAccount of the WorkloadGroup.

To make it easy to collect this information, we have provided a script, which you can download and run:

#!/bin/bash -e

SA_NAMESPACE="smm-demo"
SA_SERVICEACCOUNT="default"
SA_BEARER_TOKEN_FILE=~/bearer-token

SA_SECRET_NAME=$(kubectl get serviceaccount $SA_SERVICEACCOUNT -n $SA_NAMESPACE -o json | jq -r '.secrets[0].name')
if [ -z "$SA_SECRET_NAME" ]; then
    	echo "Cannot find secret named $SA_NAMESPACE.$SA_SERVICEACCOUNT"
    	exit 1
fi

mkdir -p $(dirname $SA_BEARER_TOKEN_FILE)
if ! kubectl get secret -n $SA_NAMESPACE ${SA_SECRET_NAME} -o json | jq -r '.data.token | @base64d' > $SA_BEARER_TOKEN_FILE ; then
    	echo "cannot get service account bearer token"
    	exit 1
fi

Step 6: Finish preparing the VM

At this point, there are a few more steps we need to take, to prepare the VM to attach to the mesh. Log into the VM and run these commands (fill in the variables with the data collected by the script in the previous step):

curl http://<dashboard-url>/get/smm-agent | bash # installs smm-agent
smm-agent set workload-group <namespace> <workloadgroup> #specifiies WorkloadGroup and namespace
smm-agent set bearer-token <token> #specifies the bearer token

You can verify that everything was set up correctly by running:

smm-agent show-config

The output should be similar to:

✓ dashboard url=http://a6bc8072e26154e5c9084e0d7f5a9c92-2016650592.eu-north-1.elb.amazonaws.com
✓ target workload-group namespace=smm-demo, name=analytics-v0
✓ no additional labels set
✓ bearer token set
✓ configuration is valid

Step 7: Attach the VM

Now, you can go ahead and attach the VM to the mesh with:

smm-agent reconcile

The output should look similar to:

✓ reconciling host operating system
✓ configuration loaded config=/etc/smm/agent.yaml
✓ install-pilot-agent ❯ downloading and installing OS package component=pilot-agent, platform={linux amd64 deb 0xc00000c168}
✓ install-pilot-agent ❯ downloader reconciles with exponential backoff downloader={pilot-agent {linux amd64 deb 0xc00000c168} true  0xc0002725b0}
...
✓ systemd-ensure-smm-agent-running/systemctl ❯ starting service args=[smm-agent]
✓ systemd-ensure-smm-agent-running/systemctl/start ❯ executing command command=systemctl, args=[start smm-agent], timeout=5m0s
✓ systemd-ensure-smm-agent-running/systemctl/start ❯ command executed successfully command=systemctl, args=[start smm-agent], stdout=, stderr=
✓ changes were made to the host operating system
✓ reconciled host operating system

Step 8: Validate your integration

Finally, to verify the setup, first run this command to check that the new WorkloadGroup exists:

kubectl get workloadentries -n smm-demo

The output should be similar to:

NAME                                	AGE 	ADDRESS
analytics-v0-3.68.232.96-vm-network-1   2m40s   3.68.232.96

You can also check the healthiness of the service with:

kubectl describe workloadentries analytics-v0-3.68.232.96-vm-network-1

Look for output such as:

Name:     	analytics-v0-3.68.232.96-vm-network-1
Namespace:	smm-demo
Labels:   	app=analytics
...
Status:
  Conditions:
	Last Probe Time:   	2022-04-01T05:47:47.472143851Z
	Last Transition Time:  2022-04-01T05:47:47.472144917Z
	Status:            	True
	Type:              	Healthy

Finally, in the Calisti dashboard, navigate to MENU > TOPOLOGY and verify that the VM is visible and that it is receiving traffic.

smm-demo

Conclusion

Congratulations, your VM is now joined to your mesh, so you can manage legacy application traffic just as seamlessly as cloud native workloads.

At this point, your work is done if you intend to operate the VM in the mesh for an extended period of time. If it’s a short-running VM that you want to remove from Istio Service Mesh, stay tuned for a future blog post that covers how to do this.

Click here to learn more about Cisco Calisti, or to use it for free.

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