Path-based Routing for AI Microservices on Kubernetes.

Question

Pulumi · Accepted Answer

Path-based routing in Kubernetes is commonly accomplished through Ingress resources. An Ingress resource manages external access to services inside a Kubernetes cluster, typically HTTP. Ingress can provide load balancing, SSL termination, and name-based virtual hosting.

In this Pulumi program, we will define an Ingress resource that establishes path-based routing to AI microservices in a Kubernetes cluster. Each path specified in the Ingress resource will correspond to a different microservice.

First, a Kubernetes `Service` is created for each microservice to expose it within the cluster. These services are responsible for load balancing the traffic and providing a stable endpoint to reach the pods comprising the microservice.

Next, an `Ingress` resource is set up to manage external access to these services. This Ingress includes rules that map incoming requests based on the path to the appropriate microservice.

Here's how you could set up path-based routing for two AI microservices named "service-a" and "service-b" using Pulumi:

```python
import pulumi
import pulumi_kubernetes as k8s

# Define a Kubernetes Service for AI Microservice A
service_a = k8s.core.v1.Service("service-a",
    spec=k8s.core.v1.ServiceSpecArgs(
        type="ClusterIP",  # Type of service is ClusterIP because it's only reachable within the cluster
        selector={"app": "microservice-a"},  # Selector for the pods this service should target
        ports=[k8s.core.v1.ServicePortArgs(
            port=80,  # The port the service is exposed on
            target_port="http",  # The target port on the pod(s)
        )],
    ))

# Define a Kubernetes Service for AI Microservice B
service_b = k8s.core.v1.Service("service-b",
    spec=k8s.core.v1.ServiceSpecArgs(
        type="ClusterIP",
        selector={"app": "microservice-b"},
        ports=[k8s.core.v1.ServicePortArgs(
            port=80,
            target_port="http",
        )],
    ))

# Define the Ingress resource to route traffic based on paths
ingress = k8s.networking.v1.Ingress("ingress",
    metadata=k8s.meta.v1.ObjectMetaArgs(
        name="path-based-ingress",
        annotations={"nginx.ingress.kubernetes.io/rewrite-target": "/"},
    ),
    spec=k8s.networking.v1.IngressSpecArgs(
        rules=[k8s.networking.v1.IngressRuleArgs(
            http=k8s.networking.v1.HTTPIngressRuleValueArgs(
                paths=[
                    k8s.networking.v1.HTTPIngressPathArgs(
                        path="/service-a",  # External path for AI Microservice A
                        path_type="Prefix",
                        backend=k8s.networking.v1.IngressBackendArgs(
                            service=k8s.networking.v1.IngressServiceBackendArgs(
                                name=service_a.metadata.name,
                                port=k8s.networking.v1.ServiceBackendPortArgs(
                                    number=80,
                                ),
                            ),
                        ),
                    ),
                    k8s.networking.v1.HTTPIngressPathArgs(
                        path="/service-b",  # External path for AI Microservice B
                        path_type="Prefix",
                        backend=k8s.networking.v1.IngressBackendArgs(
                            service=k8s.networking.v1.IngressServiceBackendArgs(
                                name=service_b.metadata.name,
                                port=k8s.networking.v1.ServiceBackendPortArgs(
                                    number=80,
                                ),
                            ),
                        ),
                    ),
                ],
            ),
        )],
    ))
```

In the above program, `service-a` and `service-b` are Kubernetes Services that expose our AI microservices within the cluster. Then we create an Ingress resource named `ingress`. The Ingress resource has rules to route traffic coming to `/service-a` to the `service-a` backend on port 80, and requests to `/service-b` go to the `service-b` backend, also on port 80.

The `nginx.ingress.kubernetes.io/rewrite-target` annotation tells the Ingress controller to strip the matched part of the path (`/service-a` or `/service-b`) before forwarding the request to the respective service. This is specific to the NGINX Ingress controller. If you're using a different Ingress controller, you'd want to adjust the annotations accordingly.

To deploy this Pulumi program, you need to have Pulumi installed and configured to communicate with your Kubernetes cluster. Once you've written the code to a file (e.g., `main.py`), you can run `pulumi up` from the command line in the same directory as your code, which will provision the resources defined in the program in your cluster.