# Rerank Module

Cohere/Jina-compatible reranking API with support for vLLM and llama.cpp backends.

## Features

- **Cohere/Jina-compatible API**: Drop-in replacement for Cohere's `/v1/rerank` endpoint
- **Multiple backends**: Support for vLLM and llama.cpp
- **High performance**: Built on FastAPI with async support
- **Production-ready**: Rate limiting, authentication, health checks

## Prerequisites

### Required

- **Linux** - Ubuntu 22.04+ or similar
- **Python 3.10+** - Managed via `uv`
- **uv** - Fast Python package manager

### Optional (for backends)

- **vLLM** - Requires NVIDIA GPU with CUDA 12.x
- **llama.cpp** - Can run on CPU or GPU

## Quick Start

### 1. Install dependencies

```bash
cd modules/rerank
uv sync --all-extras
```

### 2. Configure environment

```bash
cp .env.example .env
# Edit .env with your settings
```

### 3. Start backend server

**vLLM (GPU):**
```bash
python -m vllm.entrypoints.openai.api_server \
    --model BAAI/bge-reranker-v2-m3 \
    --host 0.0.0.0 --port 54201 \
    --task score
```

**llama.cpp (CPU):**
```bash
llama-server \
    --model /models/bge-reranker-v2-m3-q4_k_m.gguf \
    --host 0.0.0.0 --port 54210 \
    --reranking
```

### 4. Start API server

```bash
# Set required environment variables
export RERANK_DEFAULT_BACKEND=vllm
export RERANK_ENABLE_VLLM=true
export RERANK_ENABLE_LLAMACPP=false
export RERANK_EXTERNAL_URL=http://localhost:54200

# Run the server
uv run python -m rerank.cli --port 54200
```

### 5. Test the API

```bash
curl -X POST http://localhost:54200/v1/rerank \
  -H "Content-Type: application/json" \
  -d '{
    "model": "BAAI/bge-reranker-v2-m3",
    "query": "What is machine learning?",
    "documents": [
      "Machine learning is a subset of AI",
      "Cats are pets",
      "Deep learning uses neural networks"
    ]
  }'
```

## Docker Deployment

```bash
cd modules/rerank/deploy

# Copy and configure .env
cp ../.env.example .env
# Edit .env with your settings

# Start with vLLM backend
./deploy.sh --profile vllm -d

# Or start with llama.cpp backend
./deploy.sh --profile llamacpp -d

# View logs
./deploy.sh --profile vllm --logs

# Stop
./deploy.sh --profile vllm --down
```

## Python Library Usage

```python
from rerank import RerankClient

# Initialize client (reads config from environment)
client = RerankClient()

# Rerank documents
response = await client.rerank(
    query="What is machine learning?",
    documents=[
        "ML is a subset of AI",
        "Cats are pets",
        "Deep learning uses neural networks",
    ],
    model="BAAI/bge-reranker-v2-m3",
)

# Access results
for result in response.results:
    print(f"Index {result.index}: {result.relevance_score:.4f}")

# Get top N results
response = await client.rerank(
    query="programming",
    documents=["Python", "Java", "Cooking", "C++"],
    model="BAAI/bge-reranker-v2-m3",
    top_n=2,
)

# Include documents in response
response = await client.rerank(
    query="AI",
    documents=["Machine learning", "Deep learning"],
    model="BAAI/bge-reranker-v2-m3",
    return_documents=True,
)
for result in response.results:
    print(f"{result.document}: {result.relevance_score:.4f}")
```

## Configuration

All configuration is via environment variables with the `RERANK_` prefix:

| Variable | Required | Default | Description |
|----------|----------|---------|-------------|
| `RERANK_DEFAULT_BACKEND` | Yes | - | Default backend: `vllm` or `llamacpp` |
| `RERANK_ENABLE_VLLM` | Yes | - | Enable vLLM backend |
| `RERANK_ENABLE_LLAMACPP` | Yes | - | Enable llama.cpp backend |
| `RERANK_EXTERNAL_URL` | Yes | - | External URL for OpenAPI spec |
| `RERANK_PORT` | No | 54200 | API server port |
| `RERANK_VLLM_BASE_URL` | No | http://localhost:54201 | vLLM server URL |
| `RERANK_LLAMACPP_BASE_URL` | No | http://localhost:54210 | llama.cpp server URL |
| `RERANK_API_TOKENS` | No | - | Comma-separated API tokens |
| `RERANK_RATE_LIMIT_RPS` | No | 20.0 | Requests per second limit |
| `RERANK_MAX_CONCURRENT_RERANKS` | No | 20 | Max concurrent requests |

See `.env.example` for the complete list.

## Port Allocation

Following the datacenter port schema (x42xx = Reranking):

| Port | Service | Environment |
|------|---------|-------------|
| 14200 | Rerank API | Production |
| 54200 | Rerank API | Development |
| 14201 | vLLM Rerank Server | Production |
| 54201 | vLLM Rerank Server | Development |
| 14210 | llama.cpp Rerank Server | Production |
| 54210 | llama.cpp Rerank Server | Development |

## Development

```bash
# Install dev dependencies
uv sync --all-extras

# Run tests
uv run pytest

# Run tests with coverage
uv run pytest --cov=src/rerank --cov-report=term-missing

# Lint and format
uv run ruff check .
uv run ruff format .

# Type check
uv run mypy src/
```

## API Reference

See [API.md](API.md) for the complete API documentation.