@eggjs/tegg-dns-cache

@eggjs/tegg-dns-cache

DNS cache plugin for tegg framework. This plugin provides DNS caching capabilities to improve performance and reduce DNS lookup time.

Features

• DNS lookup caching with LRU algorithm
• Round-robin address rotation for load balancing
• Support both dns.lookup and dns.resolve modes
• Configurable cache TTL
• Automatic integration with egg httpclient
• Custom DNS nameservers support

Installation

npm install @eggjs/tegg-dns-cache --save

Usage

Enable Plugin

// config/plugin.js
exports.dnsCache = {
  enable: true,
  package: '@eggjs/tegg-dns-cache',
};

Configuration

// config/config.default.js
exports.dnsCache = {
  // DNS resolution mode: 'lookup' or 'resolve' (default: 'resolve')
  // - lookup: Use dns.lookup, respects /etc/hosts, but no TTL support
  // - resolve: Use dns.resolve, queries DNS directly, TTL supported
  mode: 'resolve',
  
  // Custom DNS nameservers (only for 'resolve' mode)
  dnsServers: ['8.8.8.8', '1.1.1.1'],
  
  // Maximum cache entries (default: 1000)
  maxCacheLength: 1000,
  
  // Cache lookup interval in ms (only for 'lookup' mode, default: 10000)
  lookupInterval: 10000,
  
  // Enable address rotation for multiple IPs (default: true)
  addressRotation: true,
};

DNS Resolution Modes

Resolve Mode (Recommended)

Uses dns.resolve4() to query DNS servers directly. Supports TTL from DNS records.

Advantages:

• Respects DNS TTL from authoritative servers
• More control over DNS resolution
• Can specify custom nameservers

Note: Does not respect /etc/hosts file.

exports.dnsCache = {
  mode: 'resolve',
  dnsServers: ['8.8.8.8', '1.1.1.1'], // Optional custom DNS servers
};

Lookup Mode

Uses dns.lookup() which respects system DNS configuration and /etc/hosts.

Advantages:

• Respects /etc/hosts entries
• Uses system DNS configuration

Disadvantages:

• Fixed cache interval (no real TTL)
• Less control over resolution

exports.dnsCache = {
  mode: 'lookup',
  lookupInterval: 10000, // Cache refresh interval in ms
};

API

Access DNS Resolver

// In controller or service
const resolver = this.app.dnsResolver;

// Get cached DNS record
const record = resolver.getCacheRecord('example.com');
console.log(record); // { ip: '93.184.216.34', family: 4, ttl: 60000, ... }

// Clear DNS cache
resolver.resetCache();

// Get the underlying LRU cache
const cache = resolver.getDnsCache();

Address Rotation

When a hostname resolves to multiple IP addresses, the plugin can automatically rotate through them for load balancing:

exports.dnsCache = {
  addressRotation: true, // Enable round-robin rotation
};

Each request to the same hostname will use the next IP address in rotation.

Integration with HttpClient

The plugin automatically integrates with egg's built-in httpclient. All HTTP requests will benefit from DNS caching:

// This request will use cached DNS
await this.app.httpclient.request('https://example.com/api');

Performance Benefits

• Reduced DNS lookup time: Cached DNS results eliminate network round trips
• Lower DNS server load: Fewer queries to DNS servers
• Improved request throughput: Faster connection establishment
• Load distribution: Address rotation spreads load across multiple IPs

License

MIT