dcrouter/test/suite/smtpclient_performance/test.cperf-08.dns-caching.ts

import { test } from '@git.zone/tstest/tapbundle';
import { createTestServer, createSmtpClient } from '../../helpers/utils.js';
import { Email } from '../../../ts/mail/core/classes.email.js';

test('CPERF-08: DNS Caching Efficiency Performance Tests', async () => {
  console.log('\n🌐 Testing SMTP Client DNS Caching Efficiency');
  console.log('=' .repeat(60));

  // Scenario 1: DNS Resolution Caching
  await test.test('Scenario 1: DNS Resolution Caching', async () => {
    console.log('\n🔍 Testing DNS resolution caching performance...');
    
    let dnsLookupCount = 0;
    const originalLookup = require('dns').lookup;
    
    // Mock DNS lookup to track calls
    require('dns').lookup = (hostname: string, options: any, callback: any) => {
      dnsLookupCount++;
      console.log(`  [DNS] Lookup ${dnsLookupCount} for: ${hostname}`);
      
      // Simulate DNS resolution delay
      setTimeout(() => {
        if (hostname === 'localhost' || hostname === '127.0.0.1') {
          callback(null, '127.0.0.1', 4);
        } else {
          callback(null, '127.0.0.1', 4); // Mock all domains to localhost for testing
        }
      }, 50); // 50ms DNS lookup delay
    };

    const testServer = await createTestServer({
      responseDelay: 10,
      onConnect: () => {
        console.log('  [Server] Connection established');
      }
    });

    try {
      console.log('  Creating SMTP client with connection pooling...');
      const smtpClient = createSmtpClient({
        host: testServer.hostname,
        port: testServer.port,
        secure: false,
        pool: true,
        maxConnections: 3,
        maxMessages: 100,
        // DNS caching settings
        dnsCache: true,
        dnsCacheTtl: 5000 // 5 seconds TTL
      });

      console.log('  Sending multiple emails to same domain...');
      const emails = [];
      for (let i = 0; i < 10; i++) {
        emails.push(new Email({
          from: 'sender@example.com',
          to: [`recipient${i}@example.com`],
          subject: `DNS Cache Test ${i + 1}`,
          text: `Testing DNS caching efficiency ${i + 1}`,
          messageId: `dns-cache-${i + 1}@example.com`
        }));
      }

      const startTime = Date.now();
      const promises = emails.map((email, index) => {
        return smtpClient.sendMail(email).then(result => {
          console.log(`  ✓ Email ${index + 1} sent successfully`);
          return { success: true, result };
        }).catch(error => {
          console.log(`  ✗ Email ${index + 1} failed: ${error.message}`);
          return { success: false, error };
        });
      });

      const results = await Promise.all(promises);
      const endTime = Date.now();
      
      const successful = results.filter(r => r.success).length;
      const totalTime = endTime - startTime;
      
      console.log(`  Total DNS lookups performed: ${dnsLookupCount}`);
      console.log(`  Emails sent: ${emails.length}, Successful: ${successful}`);
      console.log(`  Total time: ${totalTime}ms`);
      console.log(`  DNS cache efficiency: ${dnsLookupCount < emails.length ? 'Good' : 'Poor'}`);
      console.log(`  Expected 1-3 DNS lookups for ${emails.length} emails to same domain`);

      smtpClient.close();
    } finally {
      // Restore original DNS lookup
      require('dns').lookup = originalLookup;
      testServer.close();
    }
  });

  // Scenario 2: Multiple Domain DNS Caching
  await test.test('Scenario 2: Multiple Domain DNS Caching', async () => {
    console.log('\n🌍 Testing DNS caching across multiple domains...');
    
    let dnsLookupCount = 0;
    const dnsCache = new Map<string, { ip: string; timestamp: number }>();
    const originalLookup = require('dns').lookup;
    
    // Enhanced DNS mock with caching simulation
    require('dns').lookup = (hostname: string, options: any, callback: any) => {
      const now = Date.now();
      const cached = dnsCache.get(hostname);
      
      if (cached && (now - cached.timestamp) < 3000) { // 3 second cache
        console.log(`  [DNS] Cache hit for: ${hostname}`);
        setTimeout(() => callback(null, cached.ip, 4), 5); // Fast cache response
        return;
      }
      
      dnsLookupCount++;
      console.log(`  [DNS] Cache miss, lookup ${dnsLookupCount} for: ${hostname}`);
      
      setTimeout(() => {
        const ip = '127.0.0.1';
        dnsCache.set(hostname, { ip, timestamp: now });
        callback(null, ip, 4);
      }, 75); // Slower DNS lookup
    };

    const testServer = await createTestServer({
      responseDelay: 10
    });

    try {
      const smtpClient = createSmtpClient({
        host: testServer.hostname,
        port: testServer.port,
        secure: false,
        pool: true,
        maxConnections: 2,
        dnsCache: true,
        dnsCacheTtl: 3000
      });

      console.log('  Creating emails to multiple domains...');
      const domains = ['domain1.com', 'domain2.com', 'domain3.com'];
      const emails = [];
      
      // Create multiple emails per domain
      domains.forEach((domain, domainIndex) => {
        for (let i = 0; i < 4; i++) {
          emails.push(new Email({
            from: `sender@${domain}`,
            to: [`recipient${i}@${domain}`],
            subject: `Multi-domain DNS Test ${domainIndex + 1}-${i + 1}`,
            text: `Testing DNS caching for ${domain}`,
            messageId: `multi-dns-${domainIndex}-${i}@${domain}`
          }));
        }
      });

      console.log('  Sending emails to test DNS caching across domains...');
      const startTime = Date.now();
      
      const results = [];
      for (const email of emails) {
        try {
          const result = await smtpClient.sendMail(email);
          results.push({ success: true, result });
          console.log(`  ✓ Email to ${email.to[0]} sent`);
        } catch (error) {
          results.push({ success: false, error });
          console.log(`  ✗ Email to ${email.to[0]} failed`);
        }
        
        // Small delay between sends
        await new Promise(resolve => setTimeout(resolve, 10));
      }
      
      const endTime = Date.now();
      const successful = results.filter(r => r.success).length;
      
      console.log(`  Total DNS lookups: ${dnsLookupCount}`);
      console.log(`  Unique domains: ${domains.length}`);
      console.log(`  Total emails: ${emails.length}, Successful: ${successful}`);
      console.log(`  Total time: ${endTime - startTime}ms`);
      console.log(`  DNS cache entries: ${dnsCache.size}`);
      console.log(`  Expected ~${domains.length} DNS lookups for ${domains.length} domains`);

      smtpClient.close();
    } finally {
      require('dns').lookup = originalLookup;
      testServer.close();
    }
  });

  // Scenario 3: DNS Cache TTL and Refresh
  await test.test('Scenario 3: DNS Cache TTL and Refresh', async () => {
    console.log('\n⏰ Testing DNS cache TTL and refresh behavior...');
    
    let dnsLookupCount = 0;
    const lookupTimes: number[] = [];
    const originalLookup = require('dns').lookup;
    
    require('dns').lookup = (hostname: string, options: any, callback: any) => {
      dnsLookupCount++;
      const lookupTime = Date.now();
      lookupTimes.push(lookupTime);
      console.log(`  [DNS] Lookup ${dnsLookupCount} at ${new Date(lookupTime).toISOString().substr(11, 12)}`);
      
      setTimeout(() => {
        callback(null, '127.0.0.1', 4);
      }, 40);
    };

    const testServer = await createTestServer({
      responseDelay: 10
    });

    try {
      const smtpClient = createSmtpClient({
        host: testServer.hostname,
        port: testServer.port,
        secure: false,
        pool: true,
        maxConnections: 1,
        dnsCache: true,
        dnsCacheTtl: 1000 // 1 second TTL for testing
      });

      console.log('  Sending emails with 1.5 second intervals to test TTL...');
      
      const email1 = new Email({
        from: 'sender@ttltest.com',
        to: ['recipient1@ttltest.com'],
        subject: 'TTL Test 1',
        text: 'First email to test TTL',
        messageId: 'ttl-test-1@ttltest.com'
      });

      console.log('  Sending first email...');
      await smtpClient.sendMail(email1);
      console.log('  ✓ First email sent');

      console.log('  Waiting 500ms (within TTL)...');
      await new Promise(resolve => setTimeout(resolve, 500));

      const email2 = new Email({
        from: 'sender@ttltest.com',
        to: ['recipient2@ttltest.com'],
        subject: 'TTL Test 2',
        text: 'Second email within TTL',
        messageId: 'ttl-test-2@ttltest.com'
      });

      console.log('  Sending second email (should use cache)...');
      await smtpClient.sendMail(email2);
      console.log('  ✓ Second email sent');

      console.log('  Waiting 1000ms (TTL expiry)...');
      await new Promise(resolve => setTimeout(resolve, 1000));

      const email3 = new Email({
        from: 'sender@ttltest.com',
        to: ['recipient3@ttltest.com'],
        subject: 'TTL Test 3',
        text: 'Third email after TTL expiry',
        messageId: 'ttl-test-3@ttltest.com'
      });

      console.log('  Sending third email (should trigger new lookup)...');
      await smtpClient.sendMail(email3);
      console.log('  ✓ Third email sent');

      console.log(`  Total DNS lookups: ${dnsLookupCount}`);
      console.log(`  Expected pattern: Initial lookup -> Cache hit -> TTL refresh`);
      
      if (lookupTimes.length >= 2) {
        const timeBetweenLookups = lookupTimes[1] - lookupTimes[0];
        console.log(`  Time between DNS lookups: ${timeBetweenLookups}ms`);
        console.log(`  TTL behavior: ${timeBetweenLookups > 1000 ? 'Correct' : 'Needs review'}`);
      }

      smtpClient.close();
    } finally {
      require('dns').lookup = originalLookup;
      testServer.close();
    }
  });

  // Scenario 4: DNS Cache Memory Management
  await test.test('Scenario 4: DNS Cache Memory Management', async () => {
    console.log('\n💾 Testing DNS cache memory management and cleanup...');
    
    let dnsLookupCount = 0;
    const dnsCache = new Map();
    let cacheSize = 0;
    const originalLookup = require('dns').lookup;
    
    require('dns').lookup = (hostname: string, options: any, callback: any) => {
      dnsLookupCount++;
      
      if (!dnsCache.has(hostname)) {
        dnsCache.set(hostname, {
          ip: '127.0.0.1',
          timestamp: Date.now(),
          hits: 1
        });
        cacheSize++;
        console.log(`  [DNS] New cache entry for ${hostname} (cache size: ${cacheSize})`);
      } else {
        const entry = dnsCache.get(hostname);
        entry.hits++;
        console.log(`  [DNS] Cache hit for ${hostname} (hits: ${entry.hits})`);
      }
      
      setTimeout(() => {
        callback(null, '127.0.0.1', 4);
      }, 30);
    };

    const testServer = await createTestServer({
      responseDelay: 10
    });

    try {
      const smtpClient = createSmtpClient({
        host: testServer.hostname,
        port: testServer.port,
        secure: false,
        pool: true,
        maxConnections: 2,
        dnsCache: true,
        dnsCacheTtl: 2000,
        dnsCacheSize: 5 // Small cache size for testing
      });

      console.log('  Creating emails to many domains to test cache limits...');
      const domains = [];
      for (let i = 0; i < 8; i++) {
        domains.push(`domain${i}.example.com`);
      }

      console.log('  Sending emails to test cache memory management...');
      for (let i = 0; i < domains.length; i++) {
        const email = new Email({
          from: `sender@${domains[i]}`,
          to: [`recipient@${domains[i]}`],
          subject: `Cache Memory Test ${i + 1}`,
          text: `Testing cache for ${domains[i]}`,
          messageId: `cache-mem-${i}@${domains[i]}`
        });

        try {
          await smtpClient.sendMail(email);
          console.log(`  ✓ Email ${i + 1} to ${domains[i]} sent`);
        } catch (error) {
          console.log(`  ✗ Email ${i + 1} failed: ${error.message}`);
        }
        
        await new Promise(resolve => setTimeout(resolve, 100));
      }

      console.log('  Testing cache hit rates by resending to same domains...');
      let cacheHits = 0;
      const initialLookups = dnsLookupCount;

      for (let i = 0; i < 4; i++) { // Resend to first 4 domains
        const email = new Email({
          from: `sender@${domains[i]}`,
          to: [`recipient2@${domains[i]}`],
          subject: `Cache Hit Test ${i + 1}`,
          text: `Testing cache hits for ${domains[i]}`,
          messageId: `cache-hit-${i}@${domains[i]}`
        });

        const beforeLookups = dnsLookupCount;
        try {
          await smtpClient.sendMail(email);
          const afterLookups = dnsLookupCount;
          if (afterLookups === beforeLookups) {
            cacheHits++;
            console.log(`  ✓ Cache hit for ${domains[i]}`);
          } else {
            console.log(`  ⚡ Cache miss for ${domains[i]}`);
          }
        } catch (error) {
          console.log(`  ✗ Email failed: ${error.message}`);
        }
        
        await new Promise(resolve => setTimeout(resolve, 50));
      }

      const finalLookups = dnsLookupCount;
      console.log(`  Total DNS lookups: ${finalLookups}`);
      console.log(`  Unique domains tested: ${domains.length}`);
      console.log(`  Cache entries created: ${cacheSize}`);
      console.log(`  Cache hits on retests: ${cacheHits}/4`);
      console.log(`  Cache efficiency: ${((cacheHits / 4) * 100).toFixed(1)}%`);
      console.log(`  Memory management: ${cacheSize <= 5 ? 'Within limits' : 'Exceeded limits'}`);

      smtpClient.close();
    } finally {
      require('dns').lookup = originalLookup;
      testServer.close();
    }
  });

  // Scenario 5: DNS Resolution Performance Impact
  await test.test('Scenario 5: DNS Resolution Performance Impact', async () => {
    console.log('\n⚡ Testing DNS resolution performance impact on email sending...');
    
    let slowLookupCount = 0;
    let fastLookupCount = 0;
    const originalLookup = require('dns').lookup;
    
    // First test: Slow DNS responses
    console.log('  Phase 1: Testing with slow DNS responses (200ms delay)...');
    require('dns').lookup = (hostname: string, options: any, callback: any) => {
      slowLookupCount++;
      console.log(`  [DNS-SLOW] Lookup ${slowLookupCount} for: ${hostname}`);
      
      setTimeout(() => {
        callback(null, '127.0.0.1', 4);
      }, 200); // 200ms delay
    };

    const testServer1 = await createTestServer({
      responseDelay: 10
    });

    const smtpClient1 = createSmtpClient({
      host: testServer1.hostname,
      port: testServer1.port,
      secure: false,
      pool: false, // No pooling to force DNS lookups
      dnsCache: false
    });

    const emails1 = [];
    for (let i = 0; i < 3; i++) {
      emails1.push(new Email({
        from: 'sender@slow.example.com',
        to: [`recipient${i}@slow.example.com`],
        subject: `Slow DNS Test ${i + 1}`,
        text: `Testing slow DNS impact ${i + 1}`,
        messageId: `slow-dns-${i + 1}@slow.example.com`
      }));
    }

    const slowStartTime = Date.now();
    const slowResults = [];
    for (const email of emails1) {
      try {
        const result = await smtpClient1.sendMail(email);
        slowResults.push({ success: true });
        console.log(`  ✓ Slow DNS email sent`);
      } catch (error) {
        slowResults.push({ success: false });
        console.log(`  ✗ Slow DNS email failed`);
      }
    }
    const slowEndTime = Date.now();
    const slowTotalTime = slowEndTime - slowStartTime;

    smtpClient1.close();
    testServer1.close();

    // Second test: Fast DNS responses with caching
    console.log('  Phase 2: Testing with fast DNS responses and caching...');
    require('dns').lookup = (hostname: string, options: any, callback: any) => {
      fastLookupCount++;
      console.log(`  [DNS-FAST] Lookup ${fastLookupCount} for: ${hostname}`);
      
      setTimeout(() => {
        callback(null, '127.0.0.1', 4);
      }, 5); // 5ms delay
    };

    const testServer2 = await createTestServer({
      responseDelay: 10
    });

    const smtpClient2 = createSmtpClient({
      host: testServer2.hostname,
      port: testServer2.port,
      secure: false,
      pool: true,
      dnsCache: true,
      dnsCacheTtl: 5000
    });

    const emails2 = [];
    for (let i = 0; i < 3; i++) {
      emails2.push(new Email({
        from: 'sender@fast.example.com',
        to: [`recipient${i}@fast.example.com`],
        subject: `Fast DNS Test ${i + 1}`,
        text: `Testing fast DNS impact ${i + 1}`,
        messageId: `fast-dns-${i + 1}@fast.example.com`
      }));
    }

    const fastStartTime = Date.now();
    const fastResults = [];
    for (const email of emails2) {
      try {
        const result = await smtpClient2.sendMail(email);
        fastResults.push({ success: true });
        console.log(`  ✓ Fast DNS email sent`);
      } catch (error) {
        fastResults.push({ success: false });
        console.log(`  ✗ Fast DNS email failed`);
      }
    }
    const fastEndTime = Date.now();
    const fastTotalTime = fastEndTime - fastStartTime;

    smtpClient2.close();
    testServer2.close();

    // Performance comparison
    const slowSuccess = slowResults.filter(r => r.success).length;
    const fastSuccess = fastResults.filter(r => r.success).length;
    const performanceImprovement = ((slowTotalTime - fastTotalTime) / slowTotalTime) * 100;

    console.log(`  Slow DNS Results: ${slowTotalTime}ms, ${slowSuccess}/${emails1.length} successful`);
    console.log(`  Fast DNS Results: ${fastTotalTime}ms, ${fastSuccess}/${emails2.length} successful`);
    console.log(`  Performance improvement: ${performanceImprovement.toFixed(1)}%`);
    console.log(`  DNS lookups - Slow: ${slowLookupCount}, Fast: ${fastLookupCount}`);
    console.log(`  Caching efficiency: ${fastLookupCount < slowLookupCount ? 'Effective' : 'Needs improvement'}`);

    // Restore original DNS lookup
    require('dns').lookup = originalLookup;
  });

  console.log('\n✅ CPERF-08: DNS Caching Efficiency Performance Tests completed');
  console.log('🌐 All DNS caching scenarios tested successfully');
});