hapax

Hapax

A lightweight HTTP server for Large Language Model (LLM) interactions, built with Go.

Version

v0.0.5a

Features

• HTTP server with completion endpoint (/v1/completions)
• Health check endpoint (/health)
• Configurable server settings (port, timeouts, etc.)
• Clean shutdown handling
• Comprehensive test suite with mock LLM implementation
• Token validation with tiktoken
  • Automatic token counting
  • Context length validation
  • Max tokens validation
• Middleware architecture:
  • Request ID tracking
  • Request timing metrics
  • Panic recovery
  • CORS support
• Enhanced error handling:
  • Structured JSON error responses
  • Request ID tracking in errors
  • Zap-based logging with context
  • Custom error types for different scenarios
  • Seamless error middleware integration

Installation

go get github.com/teilomillet/hapax

Configuration

Hapax uses YAML for configuration. Here's an example configuration file:

server:
  port: 8080
  read_timeout: 30s
  write_timeout: 30s
  max_header_bytes: 1048576  # 1MB
  shutdown_timeout: 30s

llm:
  provider: ollama
  model: llama2
  endpoint: http://localhost:11434
  system_prompt: "You are a helpful assistant."
  max_context_tokens: 4096  # Maximum context length for your model
  options:
    temperature: 0.7
    max_tokens: 2000

logging:
  level: info  # debug, info, warn, error
  format: json # json, text

routes:
  - path: /v1/completions
    handler: completion
  - path: /health
    handler: health

Configuration Options

Server Configuration

• port: HTTP server port (default: 8080)
• read_timeout: Maximum duration for reading request body (default: 30s)
• write_timeout: Maximum duration for writing response (default: 30s)
• max_header_bytes: Maximum size of request headers (default: 1MB)
• shutdown_timeout: Maximum duration to wait for graceful shutdown (default: 30s)

LLM Configuration

• provider: LLM provider name (e.g., "ollama", "openai")
• model: Model name (e.g., "llama2", "gpt-4")
• endpoint: API endpoint URL
• system_prompt: Default system prompt for conversations
• max_context_tokens: Maximum context length in tokens (model-dependent)
• options: Provider-specific options
  • temperature: Sampling temperature (0.0 to 1.0)
  • max_tokens: Maximum tokens to generate

Logging Configuration

• level: Log level (debug, info, warn, error)
• format: Log format (json, text)

Quick Start

package main

import (
    "context"
    "log"

    "github.com/teilomillet/hapax"
    "github.com/teilomillet/gollm"
    "go.uber.org/zap"
)

func main() {
    // Initialize logger (optional, defaults to production config)
    logger, _ := zap.NewProduction()
    defer logger.Sync()
    hapax.SetLogger(logger)

    // Create an LLM instance (using gollm)
    llm := gollm.New()

    // Create a completion handler
    handler := hapax.NewCompletionHandler(llm)

    // Create a router
    router := hapax.NewRouter(handler)

    // Use default configuration
    config := hapax.DefaultConfig()

    // Create and start server
    server := hapax.NewServer(config, router)
    if err := server.Start(context.Background()); err != nil {
        log.Fatal(err)
    }
}

API Endpoints

POST /v1/completions

Generate completions using the configured LLM.

Request:

{
    "prompt": "Your prompt here"
}

Response:

{
    "completion": "LLM generated response"
}

Error Responses:

• 400 Bad Request: Invalid JSON or missing prompt
• 405 Method Not Allowed: Wrong HTTP method
• 500 Internal Server Error: LLM error

GET /health

Check server health status.

Response:

{
    "status": "ok"
}

Error Handling

Hapax provides structured error handling with JSON responses:

{
    "type": "validation_error",
    "message": "Invalid request format",
    "request_id": "req_123abc",
    "details": {
        "field": "prompt",
        "error": "required"
    }
}

Error types include:

• validation_error: Request validation failures
• provider_error: LLM provider issues
• rate_limit_error: Rate limiting
• internal_error: Unexpected server errors

Testing

The project includes a comprehensive test suite with a mock LLM implementation that can be used for testing LLM-dependent code:

import "github.com/teilomillet/hapax/mock_test"

// Create a mock LLM with custom response
llm := &MockLLM{
    GenerateFunc: func(ctx context.Context, p *gollm.Prompt) (string, error) {
        return "Custom response", nil
    },
}

Run the tests:

go test ./...

License

MIT License

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.