chore: setup for performance benchmarking (#3096)

# What does this PR do?
1. Added a simple mock openai-compat server that serves chat/completion
2. Add a benchmark server in EKS that includes mock inference server
3. Add locust (https://locust.io/) file for load testing

## Test Plan
bash apply.sh
kubectl port-forward service/locust-web-ui 8089:8089
Go to localhost:8089 to start a load test

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src="https://github.com/user-attachments/assets/d6aa3deb-583a-42ed-889b-751262b8e91c"
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<img width="1362" height="881" alt="image"
src="https://github.com/user-attachments/assets/6a28b9b4-05e6-44e2-b504-07e60c12d35e"
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docs/source/distributions/k8s-benchmark/apply.sh

@@ -0,0 +1,57 @@
+#!/usr/bin/env bash
+
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the terms described in the LICENSE file in
+# the root directory of this source tree.
+
+# Deploys the benchmark-specific components on top of the base k8s deployment (../k8s/apply.sh).
+
+export MOCK_INFERENCE_PORT=8080
+export STREAM_DELAY_SECONDS=0.005
+
+export POSTGRES_USER=llamastack
+export POSTGRES_DB=llamastack
+export POSTGRES_PASSWORD=llamastack
+
+export INFERENCE_MODEL=meta-llama/Llama-3.2-3B-Instruct
+export SAFETY_MODEL=meta-llama/Llama-Guard-3-1B
+
+export MOCK_INFERENCE_MODEL=mock-inference
+
+# Use llama-stack-benchmark-service as the benchmark server
+export LOCUST_HOST=http://llama-stack-benchmark-service:8323
+export LOCUST_BASE_PATH=/v1/openai/v1
+
+# Use vllm-service as the benchmark server
+# export LOCUST_HOST=http://vllm-server:8000
+# export LOCUST_BASE_PATH=/v1
+
+
+export BENCHMARK_INFERENCE_MODEL=$INFERENCE_MODEL
+
+set -euo pipefail
+set -x
+
+# Deploy benchmark-specific components
+# Deploy OpenAI mock server
+kubectl create configmap openai-mock --from-file=openai-mock-server.py \
+  --dry-run=client -o yaml | kubectl apply --validate=false -f -
+
+envsubst < openai-mock-deployment.yaml | kubectl apply --validate=false -f -
+
+# Create configmap with our custom stack config
+kubectl create configmap llama-stack-config --from-file=stack_run_config.yaml \
+  --dry-run=client -o yaml > stack-configmap.yaml
+
+kubectl apply --validate=false -f stack-configmap.yaml
+
+# Deploy our custom llama stack server (overriding the base one)
+envsubst < stack-k8s.yaml.template | kubectl apply --validate=false -f -
+
+# Deploy Locust load testing
+kubectl create configmap locust-script --from-file=locustfile.py \
+  --dry-run=client -o yaml | kubectl apply --validate=false -f -
+
+envsubst < locust-k8s.yaml | kubectl apply --validate=false -f -