AI Workload Migration Across Kubernetes Clusters

Question

Pulumi · Accepted Answer

Migrating workloads across Kubernetes clusters involves moving resources such as deployments, services, persistent volumes, secrets, and configuration from one cluster to another. Using Pulumi, this process involves several steps:

1. **Exporting Resources from the Source Cluster**: We need to capture the current state of the workloads from the source cluster. This can be done using the `pulumi stack export` command, which outputs the state of resources in a stack to a file.

2. **Modifying the Exported Stack**: The exported stack may need some modifications to fit the context of the target cluster. For example, you might need to change the resource names, namespaces, or specific annotations that are cluster-specific.

3. **Importing Resources to the Target Cluster**: With the modified stack, you can import the resources into the target cluster using the `pulumi stack import` command. This will attempt to create all the resources in the target cluster as per the modified stack file.

4. **Verifying the Migration**: After importing, it's crucial to verify that the resources are functioning correctly in the new cluster. This might involve checking the services' statuses, ensuring persistent volumes are correctly attached, and testing the applications.

Below is an example Pulumi Python program which does not perform the migration itself but sets up the necessary resources for a Kubernetes cluster that you could use in a migration. The example demonstrates how to declare a Kubernetes cluster and associated resources in Pulumi.

For migration, you would first capture the existing cluster's state, then modify the configurations to fit the new cluster's specifications and apply the modified configurations to the new cluster.

### Pulumi Python Program Setup for Kubernetes Clusters

```python
import pulumi
from pulumi_kubernetes import Provider
from pulumi_kubernetes.apps.v1 import Deployment
from pulumi_kubernetes.core.v1 import Namespace, Service

# Configure the Kubernetes provider for the source cluster
source_kubeconfig = "..."  # This should be replaced with the actual kubeconfig content or file path
source_cluster_provider = Provider("source-provider", kubeconfig=source_kubeconfig)

# Configure the Kubernetes provider for the target cluster
target_kubeconfig = "..."  # This should be replaced with the actual kubeconfig content or file path
target_cluster_provider = Provider("target-provider", kubeconfig=target_kubeconfig)

# Deploy a sample namespace to the source cluster
source_namespace = Namespace("source-namespace",
                             metadata={"name": "source-workloads"},
                             opts=pulumi.ResourceOptions(provider=source_cluster_provider))

# Deploy a sample deployment to the source cluster
source_deployment = Deployment("source-deployment",
                               metadata={"namespace": source_namespace.metadata["name"]},
                               spec={
                                   "selector": {"matchLabels": {"app": "source-app"}},
                                   "replicas": 1,
                                   "template": {
                                       "metadata": {"labels": {"app": "source-app"}},
                                       "spec": {"containers": [{"name": "nginx",
                                                                "image": "nginx"}]}
                                   }
                               },
                               opts=pulumi.ResourceOptions(provider=source_cluster_provider))

# Deploy a sample service to the source cluster
source_service = Service("source-service",
                         metadata={"namespace": source_namespace.metadata["name"]},
                         spec={
                             "selector": {"app": "source-app"},
                             "ports": [{"port": 80}]
                         },
                         opts=pulumi.ResourceOptions(provider=source_cluster_provider))

# Here you would normally have code for the target cluster resources

# Export the source deployment and service details
pulumi.export("source_deployment_name", source_deployment.metadata["name"])
pulumi.export("source_service_name", source_service.metadata["name"])
```

To perform a migration using Pulumi, you'd follow these high-level steps:
1. Use `pulumi stack export` on the source cluster to generate a stack file.
2. Modify the stack file as necessary for the target cluster's context.
3. Use `pulumi stack import` on the target cluster to initiate the migration.
4. Monitor the migration and troubleshoot any issues that arise.

Remember that actual workloads may need more detailed adjustment, including persistent volume handling, secret rotations, updating DNS entries, and ensuring consistent network policies. Always plan and test your migration strategies thoroughly in a staging environment before executing them in production.