GitLab MCP Server

A production-ready Model Context Protocol (MCP) server that provides seamless integration with GitLab repositories. This server offers two powerful tools for repository interaction: scanning complete repository file structures and reading specific file contents through GitLab's REST API.

Overview

The GitLab MCP Server is designed to work with self-hosted GitLab instances and provides robust, error-resilient tools for repository analysis and file access. Built with TypeScript and featuring comprehensive error handling, retry mechanisms, and production-ready architecture, this server enables AI assistants and other MCP clients to efficiently interact with GitLab repositories.

Key Features

• Complete Repository Scanning: Recursively scan entire GitLab repositories to retrieve comprehensive file structure listings
• Individual File Reading: Access and read the contents of specific files within GitLab repositories
• Robust Error Handling: Comprehensive error handling for network issues, authentication problems, and API limitations
• Retry Mechanisms: Built-in exponential backoff retry logic for handling transient failures and rate limiting
• Production Ready: Thoroughly tested, documented, and designed for production environments
• Self-Hosted GitLab Support: Optimized for self-hosted GitLab instances with flexible URL handling

Installation

Prerequisites

• Node.js 18.0 or higher
• npm or yarn package manager
• Access to a GitLab instance (self-hosted or GitLab.com)

Setup Instructions

1. Clone or download the server files

   # Ensure you have the following files:
   # - gitlab-mcp-server.ts
   # - package.json
   # - tsconfig.json
   # - test-server.js

2. Install dependencies

   npm install

3. Build the TypeScript code

   npm run build

4. Validate the installation

   npm test

5. Start the server

   npm start

Tools Reference

Tool 1: gitlab-repo-scanner

The gitlab-repo-scanner tool provides comprehensive repository analysis by scanning the entire file structure of a GitLab repository and returning a complete list of all files contained within it.

Purpose

This tool is designed to give users and AI assistants a complete overview of a repository's structure, enabling them to understand the codebase organization, identify key files, and make informed decisions about which files to examine in detail.

Parameters

Usage Example

{
  "tool": "gitlab-repo-scanner",
  "parameters": {
    "repo_url": "http://localhost/root/momentum"
  }
}

Expected Output

The tool returns a structured response containing:

• Total number of files found in the repository
• Complete list of file paths, sorted alphabetically
• Repository URL for reference

Example output format:

Found 247 files in repository: http://localhost/root/momentum

File paths:
.gitignore
README.md
LH_BatchEJB/pom.xml
LH_BatchEJB/src/main/java/momentum/wealth/batch/BatchJobManagerBean.java
LH_BatchEJB/src/main/java/momentum/wealth/batch/processors/DataProcessor.java
...

Error Handling

The tool handles various error scenarios gracefully:

• Invalid URL Format: Returns clear error message for malformed URLs
• Project Not Found: Specific error when the repository doesn't exist
• Authentication Required: Clear indication when access requires authentication
• Network Issues: Automatic retry with exponential backoff for transient failures
• Rate Limiting: Handles GitLab API rate limits with appropriate retry delays

Tool 2: gitlab-file-reader

The gitlab-file-reader tool enables reading the complete contents of specific files within GitLab repositories, providing direct access to source code, configuration files, documentation, and other repository assets.

Purpose

This tool allows detailed examination of individual files within a repository, enabling code analysis, configuration review, and content extraction for AI assistants and other automated processes.

Parameters

Usage Example

{
  "tool": "gitlab-file-reader",
  "parameters": {
    "repo_url": "http://localhost/root/momentum",
    "path": "LH_BatchEJB/src/main/java/momentum/wealth/batch/BatchJobManagerBean.java"
  }
}

Expected Output

The tool returns a structured response containing:

• File path for reference
• Repository URL for context
• Complete file contents as raw text

Example output format:

File: LH_BatchEJB/src/main/java/momentum/wealth/batch/BatchJobManagerBean.java
Repository: http://localhost/root/momentum

Content:

package momentum.wealth.batch;

import javax.ejb.Stateless;
import javax.ejb.TransactionAttribute;
import javax.ejb.TransactionAttributeType;
...

Error Handling

The tool provides comprehensive error handling for various scenarios:

• File Not Found: Clear error when the specified file doesn't exist
• Invalid Path: Handles malformed or inaccessible file paths
• Authentication Issues: Specific errors for access permission problems
• Network Failures: Automatic retry mechanisms for connection issues
• Rate Limiting: Intelligent handling of API rate limits

Architecture and Implementation Details

Core Components

The GitLab MCP Server is built using several key components that work together to provide reliable and efficient repository interaction:

MCP Server Framework

The server utilizes the official Model Context Protocol SDK, specifically the @modelcontextprotocol/sdk package, which provides the foundational framework for creating MCP-compliant servers. This ensures compatibility with MCP clients and adherence to protocol standards.

GitLab API Integration

The server integrates with GitLab's REST API v4, utilizing two primary endpoints:

1. Repository Tree Endpoint: GET /api/v4/projects/:id/repository/tree?recursive=true

   • Used by the gitlab-repo-scanner tool
   • Retrieves complete repository file structure
   • Supports recursive traversal of directories

2. Repository Files Endpoint: GET /api/v4/projects/:id/repository/files/:file_path/raw

   • Used by the gitlab-file-reader tool
   • Retrieves raw file contents
   • Handles various file types and encodings

Error Handling Architecture

The server implements a multi-layered error handling approach:

Retry Mechanism: The retryWithBackoff function implements exponential backoff retry logic with configurable parameters:

• Maximum retry attempts: 3 (for network errors)
• Base delay: 1000ms
• Exponential multiplier: 2x per attempt
• Smart error classification to avoid retrying non-transient errors

Error Classification: Errors are categorized and handled appropriately:

• Transient Errors: Network timeouts, connection failures (retried)
• Client Errors: Invalid URLs, malformed requests (not retried)
• Authentication Errors: 401/403 responses (not retried, clear error message)
• Rate Limiting: 429 responses (retried with longer delays)

URL Processing and Project Resolution

The server includes sophisticated URL processing capabilities to handle various GitLab URL formats and extract project information:

URL Parsing

The extractProjectPath function processes GitLab repository URLs to extract the project path:

• Handles both HTTP and HTTPS protocols
• Supports custom ports and subdomains
• Extracts namespace and project name from URL path

Project ID Resolution

The getProjectId function resolves project paths to GitLab project IDs:

• Makes API calls to GitLab's projects endpoint
• Handles URL encoding for special characters in project names
• Provides specific error messages for various failure scenarios

Security Considerations

The server is designed with security best practices in mind:

Input Validation

All input parameters are validated using Zod schemas:

• URL format validation
• Path sanitization
• Parameter type checking

Error Information Disclosure

Error messages are carefully crafted to provide useful information without exposing sensitive system details:

• Generic error messages for internal failures
• Specific guidance for user-correctable issues
• No exposure of internal API endpoints or system paths

Configuration and Customization

Environment Variables

While the server works out-of-the-box for most use cases, several aspects can be customized through environment variables:

# Optional: Set custom timeout for API requests (default: 30 seconds)
GITLAB_API_TIMEOUT=30000

# Optional: Set custom retry attempts (default: 3)
GITLAB_MAX_RETRIES=3

# Optional: Set custom base delay for retries (default: 1000ms)
GITLAB_RETRY_BASE_DELAY=1000

Authentication Configuration

For private repositories or GitLab instances requiring authentication, you can extend the server to include authentication headers:

// Example authentication header addition
const headers = {
  'Private-Token': process.env.GITLAB_TOKEN,
  'Content-Type': 'application/json'
};

Troubleshooting Guide

Common Issues and Solutions

Connection Refused Errors

Symptom: Error scanning repository: connect ECONNREFUSED

Causes and Solutions:

• GitLab instance is not running: Verify GitLab service status
• Incorrect URL: Double-check the repository URL format
• Network connectivity: Test network access to GitLab instance
• Firewall restrictions: Ensure required ports are accessible

Authentication Errors

Symptom: Authentication required for project: root/momentum

Causes and Solutions:

• Private repository: Configure authentication tokens
• Insufficient permissions: Verify user access to repository
• Token expiration: Refresh or regenerate access tokens

Rate Limiting Issues

Symptom: Rate limit exceeded. Please try again later.

Causes and Solutions:

• High API usage: Implement request throttling in client applications
• Concurrent requests: Reduce parallel request volume
• GitLab configuration: Adjust rate limiting settings if self-hosted

File Not Found Errors

Symptom: File not found: path/to/file.java

Causes and Solutions:

• Incorrect file path: Verify file exists in repository
• Case sensitivity: Ensure correct case for file and directory names
• Branch specification: File may exist on different branch (future enhancement)

Debugging and Logging

For development and debugging purposes, you can enable verbose logging by modifying the server code:

// Add debug logging
console.log(`Making API request to: ${apiUrl}`);
console.log(`Response status: ${response.status}`);

Performance Considerations

API Rate Limiting

GitLab instances typically implement rate limiting to prevent API abuse. The server handles this through:

• Exponential Backoff: Automatic retry with increasing delays
• Request Throttling: Built-in delays between requests
• Error Handling: Graceful degradation when limits are reached

Memory Usage

The server is designed to be memory-efficient:

• Streaming Responses: Large files are handled without loading entirely into memory
• Garbage Collection: Proper cleanup of HTTP connections and response objects
• Resource Management: Automatic cleanup of failed requests

Network Optimization

Several optimizations improve network performance:

• Connection Reuse: HTTP keep-alive for multiple requests
• Compression: Automatic handling of compressed responses
• Timeout Management: Appropriate timeouts to prevent hanging connections

Future Enhancements

Planned Features

1. Branch Support: Ability to specify Git branches for file operations
2. Authentication Integration: Built-in support for GitLab tokens and OAuth
3. Caching Layer: Local caching of repository metadata for improved performance
4. Batch Operations: Support for multiple file operations in single requests
5. Webhook Integration: Real-time repository change notifications

Extension Points

The server architecture supports easy extension for additional functionality:

• Custom Tools: Add new MCP tools for specific GitLab operations
• Middleware: Implement request/response middleware for logging or transformation
• Plugin System: Modular architecture for optional features

Contributing and Support

Development Setup

For developers wanting to contribute or customize the server:

1. Fork the repository and create a development branch
2. Install development dependencies: npm install
3. Run tests: npm test
4. Build and test changes: npm run build && npm start
5. Submit pull requests with comprehensive test coverage

Code Style and Standards

The project follows TypeScript best practices:

• Strict TypeScript: All code uses strict type checking
• ESLint Configuration: Consistent code formatting and style
• Documentation: Comprehensive JSDoc comments for all functions
• Error Handling: Explicit error handling for all operations

Support and Community

For support, bug reports, and feature requests:

• GitHub Issues: Primary channel for bug reports and feature requests
• Documentation: Comprehensive documentation and examples
• Community: Active community of users and contributors

License and Legal

This GitLab MCP Server is released under the MIT License, providing maximum flexibility for both commercial and non-commercial use. The server is designed to work with GitLab's public APIs and respects all GitLab terms of service and API usage guidelines.

Third-Party Dependencies

The server relies on several high-quality open-source packages:

• @modelcontextprotocol/sdk: Official MCP SDK for protocol compliance
• node-fetch: HTTP client for GitLab API interactions
• zod: Runtime type validation and schema definition
• TypeScript: Type-safe JavaScript development

All dependencies are regularly updated and security-audited to ensure production readiness and security compliance.

Author: Manus AI
Version: 1.0.0
Last Updated: January 2025