API Gateway Operations

This guide provides comprehensive guidance for operating API gateways to secure Model Context Protocol (MCP) server traffic. Since most MCP traffic is TLS-encrypted and uninspectable at the network level, API gateways are essential for gaining visibility and control over MCP server communications.

Community Discussion

💬 API Gateway Operations Discussions - Share your API gateway configurations, traffic policies, and operational experiences with the community.

Why API Gateways Are Critical for MCP Security

The TLS Inspection Problem

Most MCP traffic is encrypted and uninspectable:

• HTTPS Everywhere - MCP servers communicate with external services via HTTPS
• Network Monitoring Blind Spots - Traditional network security tools can’t inspect encrypted payloads
• Agent Communication - AI agents make API calls to multiple external services simultaneously
• No Traffic Visibility - Without an API gateway, you can’t see what data is being sent/received

API Gateway Solutions

API gateways provide essential security capabilities:

• Traffic Decryption - Decrypt incoming traffic for inspection, then re-encrypt for external services
• Policy Enforcement - Apply security policies to API calls before they reach external services
• Audit Logging - Log all API interactions for security monitoring and compliance
• Rate Limiting - Control API usage to prevent abuse and resource exhaustion
• Access Control - Authenticate and authorize API calls based on policies

API Gateway Architecture Patterns

MCP Server → API Gateway → External Services

┌─────────────┐    ┌─────────────┐    ┌─────────────┐
│ MCP Server  │───▶│ API Gateway │───▶│ External    │
│             │    │             │    │ Services    │
└─────────────┘    └─────────────┘    └─────────────┘
                          │
                          ▼
                   ┌─────────────┐
                   │ Security    │
                   │ Logging &   │
                   │ Monitoring  │
                   └─────────────┘

Benefits of This Architecture

• Complete Visibility - All external API calls are logged and monitored
• Policy Enforcement - Security policies applied to all outbound traffic
• Centralized Security - Single point for security controls and monitoring
• Compliance - Audit trail of all external API interactions

Popular API Gateway Solutions

Kong Gateway

# docker-compose.yml
version: '3.8'
services:
  kong:
    image: kong:latest
    environment:
      - KONG_DATABASE=off
      - KONG_DECLARATIVE_CONFIG=/kong/declarative/kong.yml
      - KONG_PROXY_ACCESS_LOG=/dev/stdout
      - KONG_ADMIN_ACCESS_LOG=/dev/stdout
      - KONG_PROXY_ERROR_LOG=/dev/stderr
      - KONG_ADMIN_ERROR_LOG=/dev/stderr
    ports:
      - "8000:8000"  # Proxy port
      - "8001:8001"  # Admin API
    volumes:
      - ./kong.yml:/kong/declarative/kong.yml

Kong Configuration Example

# kong.yml
_format_version: "3.0"
_transform: true

services:
  - name: external-api-service
    url: https://api.external-service.com
    plugins:
      - name: rate-limiting
        config:
          minute: 100
          hour: 1000
      - name: request-size-limiting
        config:
          allowed_payload_size: 10
      - name: response-size-limiting
        config:
          allowed_payload_size: 50

routes:
  - name: external-api-route
    service: external-api-service
    paths:
      - /external-api

Nginx with OpenResty

# nginx.conf
events {
    worker_connections 1024;
}

http {
    # Logging for security monitoring
    log_format mcp_access '$remote_addr - $remote_user [$time_local] '
                         '"$request" $status $body_bytes_sent '
                         '"$http_referer" "$http_user_agent" '
                         '"$upstream_addr" "$upstream_response_time"';

    access_log /var/log/nginx/mcp_access.log mcp_access;

    # Rate limiting
    limit_req_zone $binary_remote_addr zone=api_limit:10m rate=10r/s;

    upstream external_service {
        server api.external-service.com:443;
    }

    server {
        listen 8080;
        
        # Apply rate limiting
        limit_req zone=api_limit burst=20 nodelay;
        
        location /api/ {
            # Security headers
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto $scheme;
            
            # Proxy to external service
            proxy_pass https://external_service/;
            proxy_ssl_verify on;
            proxy_ssl_trusted_certificate /etc/ssl/certs/ca-certificates.crt;
            
            # Request/response size limits
            client_max_body_size 10M;
            proxy_buffering on;
            proxy_buffer_size 4k;
            proxy_buffers 8 4k;
        }
    }
}

Configuring MCP Servers to Use API Gateways

Environment Variable Configuration

# Set proxy environment variables
export HTTP_PROXY=http://api-gateway:8080
export HTTPS_PROXY=http://api-gateway:8080
export NO_PROXY=localhost,127.0.0.1,.local

Python MCP Server Configuration

import os
import requests
from requests.adapters import HTTPAdapter
from urllib3.util.retry import Retry

class MCPServer:
    def __init__(self):
        self.session = requests.Session()
        
        # Configure proxy settings
        proxies = {
            'http': os.environ.get('HTTP_PROXY'),
            'https': os.environ.get('HTTPS_PROXY')
        }
        
        if proxies['http'] or proxies['https']:
            self.session.proxies.update(proxies)
        
        # Configure retry strategy
        retry_strategy = Retry(
            total=3,
            backoff_factor=1,
            status_forcelist=[429, 500, 502, 503, 504]
        )
        
        adapter = HTTPAdapter(max_retries=retry_strategy)
        self.session.mount("http://", adapter)
        self.session.mount("https://", adapter)
    
    def make_api_call(self, url, data=None):
        """Make API call through gateway"""
        try:
            response = self.session.post(url, json=data, timeout=30)
            response.raise_for_status()
            return response.json()
        except requests.exceptions.RequestException as e:
            # Log error for security monitoring
            print(f"API call failed: {e}")
            raise

Node.js MCP Server Configuration

const axios = require('axios');
const HttpsProxyAgent = require('https-proxy-agent');

class MCPServer {
    constructor() {
        const proxyUrl = process.env.HTTPS_PROXY || process.env.HTTP_PROXY;
        
        this.httpClient = axios.create({
            timeout: 30000,
            httpsAgent: proxyUrl ? new HttpsProxyAgent(proxyUrl) : undefined
        });
        
        // Add request interceptor for logging
        this.httpClient.interceptors.request.use(
            (config) => {
                console.log(`API Request: ${config.method.toUpperCase()} ${config.url}`);
                return config;
            },
            (error) => {
                console.error('Request error:', error);
                return Promise.reject(error);
            }
        );
    }
    
    async makeApiCall(url, data = null) {
        try {
            const response = await this.httpClient.post(url, data);
            return response.data;
        } catch (error) {
            console.error('API call failed:', error.message);
            throw error;
        }
    }
}

Security Policies and Rules

Rate Limiting Policies

# Kong plugin configuration
plugins:
  - name: rate-limiting
    config:
      minute: 100
      hour: 1000
      policy: local
      hide_client_headers: false
      fault_tolerant: true

Request/Response Size Limits

# Kong plugin configuration
plugins:
  - name: request-size-limiting
    config:
      allowed_payload_size: 10  # 10MB
  - name: response-size-limiting
    config:
      allowed_payload_size: 50  # 50MB

IP Whitelisting

# Kong plugin configuration
plugins:
  - name: ip-restriction
    config:
      allow:
        - 10.0.0.0/8
        - 172.16.0.0/12
        - 192.168.0.0/16

Monitoring and Alerting

Security Monitoring

# Monitor API gateway logs for security events
tail -f /var/log/kong/access.log | grep -E "(40[0-9]|50[0-9])" | \
while read line; do
    echo "Security Alert: $line"
    # Send to security monitoring system
done

Prometheus Metrics

# Kong Prometheus plugin
plugins:
  - name: prometheus
    config:
      per_consumer: true
      status_code_metrics: true
      latency_metrics: true
      bandwidth_metrics: true

Log Analysis

# Analyze API gateway logs for suspicious patterns
awk '
    /429/ { rate_limit_exceeded++ }
    /401|403/ { auth_failures++ }
    /50[0-9]/ { server_errors++ }
    END {
        print "Rate limit violations:", rate_limit_exceeded
        print "Authentication failures:", auth_failures
        print "Server errors:", server_errors
    }
' /var/log/kong/access.log

Traffic Inspection and Analysis

Request/Response Logging

# Kong plugin for detailed logging
plugins:
  - name: file-log
    config:
      path: /var/log/kong/requests.log
      custom_fields_by_lua:
        request_body: "return kong.request.get_raw_body()"
        response_body: "return kong.response.get_raw_body()"

Content Filtering

-- Kong custom plugin for content filtering
local ContentFilter = {
    VERSION = "1.0.0",
    PRIORITY = 1000,
}

function ContentFilter:access(conf)
    local body = kong.request.get_raw_body()
    
    -- Check for suspicious content
    if body and string.find(body, "malicious_pattern") then
        return kong.response.exit(400, {
            message = "Request blocked by content filter"
        })
    end
end

return ContentFilter

Performance Optimization

Caching Strategies

# Kong caching plugin
plugins:
  - name: proxy-cache
    config:
      response_code:
        - 200
        - 301
        - 302
      request_method:
        - GET
        - HEAD
      content_type:
        - text/plain
        - application/json
      cache_ttl: 300  # 5 minutes

Load Balancing

# Kong upstream configuration
upstreams:
  - name: external-service-upstream
    algorithm: round-robin
    healthchecks:
      active:
        healthy:
          interval: 30
          successes: 2
        unhealthy:
          interval: 30
          http_failures: 3
    targets:
      - target: api1.external-service.com:443
        weight: 100
      - target: api2.external-service.com:443
        weight: 100

Troubleshooting Common Issues

Connectivity Problems

# Test API gateway connectivity
curl -v http://api-gateway:8000/health

# Check proxy configuration
docker exec mcp-server env | grep -i proxy

# Test external service connectivity through gateway
curl -v -H "Host: api.external-service.com" http://api-gateway:8000/api/test

Performance Issues

# Monitor API gateway performance
docker stats kong

# Check response times
curl -o /dev/null -s -w "Connect: %{time_connect} Start Transfer: %{time_starttransfer} Total: %{time_total}\n" http://api-gateway:8000/api/test

Contributing

Help improve our API gateway operations guidance by sharing:

• Gateway Configurations - Working configurations for different API gateway solutions
• Security Policies - Effective security policies and rules
• Monitoring Setups - Comprehensive monitoring and alerting configurations
• Performance Optimizations - Techniques for optimizing API gateway performance

This page is being developed with community input. Share your API gateway experience in our discussions.