From 2f80a536c39d767775a03e76c7dfdbde71bcb704 Mon Sep 17 00:00:00 2001
From: fallenbagel <98979876+Fallenbagel@users.noreply.github.com>
Date: Mon, 20 Jan 2025 16:53:12 +0800
Subject: [PATCH] feat: simple implementation of dnscaching

---
 server/utils/dnsCacheManager.ts | 122 ++++++++++++++++++++++++++++++++
 1 file changed, 122 insertions(+)
 create mode 100644 server/utils/dnsCacheManager.ts

diff --git a/server/utils/dnsCacheManager.ts b/server/utils/dnsCacheManager.ts
new file mode 100644
index 000000000..70138b3fd
--- /dev/null
+++ b/server/utils/dnsCacheManager.ts
@@ -0,0 +1,122 @@
+import logger from '@server/logger';
+import { LRUCache } from 'lru-cache';
+import dns from 'node:dns';
+
+interface DnsCache {
+  address: string;
+  family: number;
+  timestamp: number;
+}
+
+interface CacheStats {
+  hits: number;
+  misses: number;
+}
+
+class DnsCacheManager {
+  private cache: LRUCache<string, DnsCache>;
+  private lookupAsync: typeof dns.promises.lookup;
+  private stats: CacheStats = {
+    hits: 0,
+    misses: 0,
+  };
+
+  constructor(ttlMs = 300000) {
+    this.cache = new LRUCache<string, DnsCache>({ max: 500, ttl: ttlMs });
+    this.lookupAsync = dns.promises.lookup;
+  }
+
+  async lookup(hostname: string): Promise<DnsCache> {
+    const cached = this.cache.get(hostname);
+    if (cached) {
+      this.stats.hits++;
+      logger.debug(`DNS cache hit for ${hostname}`, {
+        label: 'DNSCache',
+        address: cached.address,
+        family: cached.family,
+        age: Date.now() - cached.timestamp,
+      });
+      return cached;
+    }
+
+    this.stats.misses++;
+    try {
+      const result = await this.lookupAsync(hostname);
+      const dnsCache: DnsCache = {
+        address: result.address,
+        family: result.family,
+        timestamp: Date.now(),
+      };
+
+      this.cache.set(hostname, dnsCache);
+      logger.debug(`DNS cache miss for ${hostname}, cached new result`, {
+        label: 'DNSCache',
+        address: dnsCache.address,
+        family: dnsCache.family,
+      });
+      return dnsCache;
+    } catch (error) {
+      throw new Error(`DNS lookup failed for ${hostname}: ${error.message}`);
+    }
+  }
+
+  getStats() {
+    const entries = [...this.cache.entries()];
+    return {
+      size: entries.length,
+      maxSize: this.cache.max,
+      hits: this.stats.hits,
+      misses: this.stats.misses,
+      hitRate: this.stats.hits / (this.stats.hits + this.stats.misses || 1),
+    };
+  }
+
+  getCacheEntries() {
+    const entries: Record<
+      string,
+      {
+        address: string;
+        family: number;
+        age: number;
+        ttl: number;
+      }
+    > = {};
+
+    for (const [hostname, data] of this.cache.entries()) {
+      const age = Date.now() - data.timestamp;
+      const ttl = (this.cache.ttl ?? 300000) - age;
+
+      entries[hostname] = {
+        address: data.address,
+        family: data.family,
+        age,
+        ttl,
+      };
+    }
+
+    return entries;
+  }
+
+  getCacheEntry(hostname: string) {
+    const entry = this.cache.get(hostname);
+    if (!entry) {
+      return null;
+    }
+
+    return {
+      address: entry.address,
+      family: entry.family,
+      age: Date.now() - entry.timestamp,
+      ttl: (this.cache.ttl ?? 300000) - (Date.now() - entry.timestamp),
+    };
+  }
+
+  clear() {
+    this.cache.clear();
+    this.stats.hits = 0;
+    this.stats.misses = 0;
+    logger.debug('DNS cache cleared', { label: 'DNSCache' });
+  }
+}
+
+export const dnsCache = new DnsCacheManager();