Add inference extension doc

Author: bjee19

content/ngf/how-to/gateway-api-inference-extension.md

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+---
+title: Gateway API Inference Extension
+weight: 800
+toc: true
+type: how-to
+product: NGF
+nd-docs: DOCS-0000
+---
+
+Learn how to use NGINX Gateway Fabric with the Gateway API Inference Extension to optimize traffic routing to self-hosting Generative AI Models on Kubernetes. 
+
+## Overview
+
+The [Gateway API Inference Extension](https://gateway-api-inference-extension.sigs.k8s.io/) is an official Kubernetes project that aims to provide optimized load-balancing for self-hosted Generative AI Models on Kubernetes. 
+The project's goal is to improve and standardize routing to inference workloads across the ecosystem. 
+
+Coupled with the provided Endpoint Picker Service, NGINX Gataway Fabric becomes an [Inference Gateway](https://gateway-api-inference-extension.sigs.k8s.io/#concepts-and-definitions), with additional AI specific traffic management features such as model-aware routing, serving priority for models, model rollouts, and more. 
+
+{{< call-out "warning" >}} The Gateway API Inference Extension is still in alpha status and should not be used in production yet.{{< /call-out >}}
+
+## Setup
+
+- Install the Gateway API Inference Extension CRDs:
+
+```shell
+kubectl apply -f https://github.com/kubernetes-sigs/gateway-api-inference-extension/releases/latest/download/manifests.yaml
+```
+
+- To enable the Gateway API Inference Extension, [install]({{< ref "/ngf/install/" >}}) NGINX Gateway Fabric with these modifications:
+  - Using Helm: set the `nginxGateway.gwAPIInferenceExtension.enable=true` Helm value.
+  - Using Kubernetes manifests: set the `--gateway-api-inference-extension` flag in the nginx-gateway container argument, update the ClusterRole RBAC to add the `inferncepools`:
+  ```yaml
+    - apiGroups:
+        - inference.networking.k8s.io
+        resources:
+        - inferencepools
+        verbs:
+        - get
+        - list
+        - watch
+    - apiGroups:
+        - inference.networking.k8s.io
+        resources:
+        - inferencepools/status
+        verbs:
+        - update
+  ```
+
+  See this [example manifest](https://raw.githubusercontent.com/nginx/nginx-gateway-fabric/main/deploy/inference/deploy.yaml) for clarification.
+
+
+## Deploy a sample model server
+
+The [vLLM simulator](https://github.com/llm-d/llm-d-inference-sim/tree/main) model server does not use GPUs and is ideal for test/dev environments. This sample is configured to simulate the [meta-llama/LLama-3.1-8B-Instruct](https://huggingface.co/meta-llama/Llama-3.1-8B-Instruct) model. To deploy the vLLM simulator, run the following command:
+
+```shell
+kubectl apply -f https://github.com/kubernetes-sigs/gateway-api-inference-extension/raw/main/config/manifests/vllm/sim-deployment.yaml
+```
+
+## Deploy the InferencePool and Endpoint Picker Extension
+
+The InferencePool is a Gateway API Inference Extension resource that represents a set of Infernece-focused Pods. With InferencePool, you can configure a routing extension as well as inference-specific routing optimizations. For more information on this resource, refer to the Gateway API Inference Extension [InferencePool documentation](https://gateway-api-inference-extension.sigs.k8s.io/api-types/inferencepool/).
+
+Install an InferencePool named `vllm-llama3-8b-instruct` that selects from endpoints with label `app: vllm-llama3-8b-instruct` and listening on port 8000. The Helm install command automatically installs the Endpoint Picker Extension and InferencePool.
+
+NGINX will query the Endpoint Picker Extension to determine the appropriate pod endpoint to route traffic to. These pods are selected from a pool of ready pods designated by the assigned InferencePool's Selector field. For more information on the [Endpoint Picker](https://github.com/kubernetes-sigs/gateway-api-inference-extension/blob/main/pkg/epp/README.md).
+
+{{< call-out "warning" >}} The Endpoint Picker Extension is a third-party application written and provided by the Gateway API Inference Extension project. The communication between NGINX and the Endpoint Picker Extension does not currently have TLS support, so it is an insecure connection. The Gateway API Inference Extension is still in alpha status and should not be used in production yet. NGINX Gateway Fabric is not responsible for any threats or risks associated with using this third-party Endpoint Picker Extension application. {{< /call-out >}}
+
+```shell
+export IGW_CHART_VERSION=v1.0.1
+helm install vllm-llama3-8b-instruct \
+--set inferencePool.modelServers.matchLabels.app=vllm-llama3-8b-instruct \
+--version $IGW_CHART_VERSION \
+oci://registry.k8s.io/gateway-api-inference-extension/charts/inferencepool
+```
+
+## Deploy an Inference Gateway
+
+1. Deploy Inference Gateway:
+
+```shell
+kubectl apply -f https://raw.githubusercontent.com/nginx/nginx-gateway-fabric/v{{< version-ngf >}}/examples/inference/gateway.yaml
+```
+
+Confirm that the Gateway was assigned an IP address and reports a `Programmed=True` status:
+
+```shell
+kubectl describe gateway inference-gateway
+```
+
+Save the public IP address and port of the NGINX Service into shell variables:
+
+```text
+GW_IP=XXX.YYY.ZZZ.III
+GW_PORT=<port number>
+```
+
+2. Deploy the HTTPRoute:
+
+```shell
+kubectl apply -f https://raw.githubusercontent.com/nginx/nginx-gateway-fabric/v{{< version-ngf >}}/examples/snippets-filter/httproute.yaml
+```
+
+Confirm that the HTTPRoute status conditions include `Accepted=True` and `ResolvedRefs=True`:
+
+```shell
+kubectl describe httproute llm-route
+```
+
+## Try it out
+
+Send traffic to the Gateway: 
+
+```shell
+curl -i $GW_IP:$GW_PORT/v1/completions -H 'Content-Type: application/json' -d '{
+"model": "food-review-1",
+"prompt": "Write as if you were a critic: San Francisco",
+"max_tokens": 100,
+"temperature": 0
+}'
+```
+
+## Cleanup
+
+1. Uninstall the InferencePool, InferenceObjective, and model server resources:
+
+
+```shell
+helm uninstall vllm-llama3-8b-instruct
+kubectl delete -f https://github.com/kubernetes-sigs/gateway-api-inference-extension/raw/main/config/manifests/inferenceobjective.yaml --ignore-not-found
+kubectl delete -f https://github.com/kubernetes-sigs/gateway-api-inference-extension/raw/main/config/manifests/vllm/cpu-deployment.yaml --ignore-not-found
+kubectl delete -f https://github.com/kubernetes-sigs/gateway-api-inference-extension/raw/main/config/manifests/vllm/gpu-deployment.yaml --ignore-not-found
+kubectl delete -f https://github.com/kubernetes-sigs/gateway-api-inference-extension/raw/main/config/manifests/vllm/sim-deployment.yaml --ignore-not-found
+```
+
+2. Uninstall the Gateway API Inference Extension CRDs:
+
+```shell
+kubectl delete -k https://github.com/kubernetes-sigs/gateway-api-inference-extension/config/crd --ignore-not-found
+```
+
+3. Uninstall Inference Gateway and HTTPRoute:
+
+```shell
+kubectl delete -f https://raw.githubusercontent.com/nginx/nginx-gateway-fabric/v{{< version-ngf >}}/examples/inference/gateway.yaml
+kubectl delete -f https://raw.githubusercontent.com/nginx/nginx-gateway-fabric/v{{< version-ngf >}}/examples/snippets-filter/httproute.yaml
+```
+
+4. Uninstall NGINX Gateway Fabric:
+
+```shell
+helm uninstall ngf -n nginx-gateway
+```
+If needed, replace ngf with your chosen release name.
+
+5. Remove namespace and NGINX Gateway Fabric CRDs:
+
+```shell
+kubectl delete ns nginx-gateway
+kubectl delete -f https://raw.githubusercontent.com/nginx/nginx-gateway-fabric/v{{< version-ngf >}}/deploy/crds.yaml
+```
+
+6. Remove the Gateway API CRDs:
+
+{{< include "/ngf/installation/uninstall-gateway-api-resources.md" >}}
+
+## See also
+
+- [Gateway API Inference Exntension Introduction](https://gateway-api-inference-extension.sigs.k8s.io/): for introductory details to the project.
+- [Gateway API Inference Extension API Overview](https://gateway-api-inference-extension.sigs.k8s.io/concepts/api-overview/): for an API overview.
+- [Gateway API Inference Extension User Guides](https://gateway-api-inference-extension.sigs.k8s.io/guides/): for additional use cases and guides.