Chat Handler

Text-based chat pipeline for the DaviesTechLabs AI/ML platform.

Overview

A NATS-based service that handles chat completion requests with RAG (Retrieval Augmented Generation).

Pipeline: Query → Embeddings → Milvus → Rerank → LLM → (optional TTS)

Versions

File	Description
chat_handler.py	Standalone implementation (v1)
chat_handler_v2.py	Uses handler-base library (recommended)
Dockerfile	Standalone image
Dockerfile.v2	Handler-base image

Architecture

NATS (ai.chat.request)
        │
        ▼
┌───────────────────┐
│   Chat Handler    │
└───────────────────┘
        │
        ├──▶ BGE Embeddings (drizzt)
        │         │
        │         ▼
        ├──▶ Milvus Vector Search
        │         │
        │         ▼
        ├──▶ BGE Reranker (danilo)
        │         │
        │         ▼
        ├──▶ vLLM (khelben)
        │         │
        │         ▼ (optional)
        └──▶ XTTS TTS (elminster)
                  │
                  ▼
         NATS (ai.chat.response.{id})

NATS Message Format

Request (ai.chat.request)

{
  "request_id": "uuid",
  "query": "What is the capital of France?",
  "collection": "knowledge_base",
  "enable_tts": false,
  "system_prompt": "Optional custom system prompt"
}

Response (ai.chat.response.{request_id})

{
  "request_id": "uuid",
  "response": "The capital of France is Paris.",
  "sources": [
    {"text": "Paris is the capital...", "score": 0.95}
  ],
  "audio": "base64-encoded-audio (if TTS enabled)"
}

Configuration

Environment Variable	Default	Description
NATS_URL	nats://nats.ai-ml.svc.cluster.local:4222	NATS server
EMBEDDINGS_URL	http://embeddings-predictor.ai-ml.svc.cluster.local	Embeddings
RERANKER_URL	http://reranker-predictor.ai-ml.svc.cluster.local	Reranker
VLLM_URL	http://llm-draft.ai-ml.svc.cluster.local:8000	LLM service
TTS_URL	http://tts-predictor.ai-ml.svc.cluster.local	TTS (optional)
MILVUS_HOST	milvus.ai-ml.svc.cluster.local	Vector DB
COLLECTION_NAME	knowledge_base	Default Milvus collection
ENABLE_TTS	false	Enable audio responses

Building

# Standalone image (v1)
docker build -f Dockerfile -t chat-handler:latest .

# Handler-base image (v2 - recommended)
docker build -f Dockerfile.v2 -t chat-handler:v2 .

Dependencies

The v2 handler depends on handler-base:

pip install git+https://git.daviestechlabs.io/daviestechlabs/handler-base.git

Related

• handler-base - Base handler library
• voice-assistant - Voice pipeline
• homelab-design - Architecture docs