lws.md

(deployment-lws)=

# LWS

LeaderWorkerSet (LWS) is a Kubernetes API that aims to address common deployment patterns of AI/ML inference workloads.
A major use case is for multi-host/multi-node distributed inference.

vLLM can be deployed with [LWS](https://github.com/kubernetes-sigs/lws) on Kubernetes for distributed model serving.

## Prerequisites

* At least two Kubernetes nodes, each with 8 GPUs, are required.
* Install LWS by following the instructions found [here](https://lws.sigs.k8s.io/docs/installation/).

## Deploy and Serve

Deploy the following yaml file `lws.yaml`

```yaml
apiVersion: leaderworkerset.x-k8s.io/v1
kind: LeaderWorkerSet
metadata:
  name: vllm
spec:
  replicas: 2
  leaderWorkerTemplate:
    size: 2
    restartPolicy: RecreateGroupOnPodRestart
    leaderTemplate:
      metadata:
        labels:
          role: leader
      spec:
        containers:
          - name: vllm-leader
            image: docker.io/vllm/vllm-openai:latest
            env:
              - name: HUGGING_FACE_HUB_TOKEN
                value: <your-hf-token>
            command:
              - sh
              - -c
              - "bash /vllm-workspace/examples/online_serving/multi-node-serving.sh leader --ray_cluster_size=$(LWS_GROUP_SIZE); 
                 python3 -m vllm.entrypoints.openai.api_server --port 8080 --model meta-llama/Meta-Llama-3.1-405B-Instruct --tensor-parallel-size 8 --pipeline_parallel_size 2"
            resources:
              limits:
                nvidia.com/gpu: "8"
                memory: 1124Gi
                ephemeral-storage: 800Gi
              requests:
                ephemeral-storage: 800Gi
                cpu: 125
            ports:
              - containerPort: 8080
            readinessProbe:
              tcpSocket:
                port: 8080
              initialDelaySeconds: 15
              periodSeconds: 10
            volumeMounts:
              - mountPath: /dev/shm
                name: dshm
        volumes:
        - name: dshm
          emptyDir:
            medium: Memory
            sizeLimit: 15Gi
    workerTemplate:
      spec:
        containers:
          - name: vllm-worker
            image: docker.io/vllm/vllm-openai:latest
            command:
              - sh
              - -c
              - "bash /vllm-workspace/examples/online_serving/multi-node-serving.sh worker --ray_address=$(LWS_LEADER_ADDRESS)"
            resources:
              limits:
                nvidia.com/gpu: "8"
                memory: 1124Gi
                ephemeral-storage: 800Gi
              requests:
                ephemeral-storage: 800Gi
                cpu: 125
            env:
              - name: HUGGING_FACE_HUB_TOKEN
                value: <your-hf-token>
            volumeMounts:
              - mountPath: /dev/shm
                name: dshm   
        volumes:
        - name: dshm
          emptyDir:
            medium: Memory
            sizeLimit: 15Gi
---
apiVersion: v1
kind: Service
metadata:
  name: vllm-leader
spec:
  ports:
    - name: http
      port: 8080
      protocol: TCP
      targetPort: 8080
  selector:
    leaderworkerset.sigs.k8s.io/name: vllm
    role: leader
  type: ClusterIP
```

```bash
kubectl apply -f lws.yaml
```

Verify the status of the pods:

```bash
kubectl get pods
```

Should get an output similar to this:

```bash
NAME       READY   STATUS    RESTARTS   AGE
vllm-0     1/1     Running   0          2s
vllm-0-1   1/1     Running   0          2s
vllm-1     1/1     Running   0          2s
vllm-1-1   1/1     Running   0          2s
```

Verify that the distributed tensor-parallel inference works:

```bash
kubectl logs vllm-0 |grep -i "Loading model weights took" 
```

Should get something similar to this:

```text
INFO 05-08 03:20:24 model_runner.py:173] Loading model weights took 0.1189 GB
(RayWorkerWrapper pid=169, ip=10.20.0.197) INFO 05-08 03:20:28 model_runner.py:173] Loading model weights took 0.1189 GB
```

## Access ClusterIP service

```bash
# Listen on port 8080 locally, forwarding to the targetPort of the service's port 8080 in a pod selected by the service
kubectl port-forward svc/vllm-leader 8080:8080
```

The output should be similar to the following:

```text
Forwarding from 127.0.0.1:8080 -> 8080
Forwarding from [::1]:8080 -> 8080
```

## Serve the model

Open another terminal and send a request

```text
curl http://localhost:8080/v1/completions \
-H "Content-Type: application/json" \
-d '{
    "model": "meta-llama/Meta-Llama-3.1-405B-Instruct",
    "prompt": "San Francisco is a",
    "max_tokens": 7,
    "temperature": 0
}'
```

The output should be similar to the following

```text
{
  "id": "cmpl-1bb34faba88b43f9862cfbfb2200949d",
  "object": "text_completion",
  "created": 1715138766,
  "model": "meta-llama/Meta-Llama-3.1-405B-Instruct",
  "choices": [
    {
      "index": 0,
      "text": " top destination for foodies, with",
      "logprobs": null,
      "finish_reason": "length",
      "stop_reason": null
    }
  ],
  "usage": {
    "prompt_tokens": 5,
    "total_tokens": 12,
    "completion_tokens": 7
  }
}
```