Add entry source, either cache or query (#63)

README.md

@@ -156,6 +156,12 @@ The timestamp (`Date.now() + ttl * 1000`) when the entry expires.
 
 The time in seconds for its lifetime.
 
+#### source
+
+**Note**: This is not present when falling back to `dns.lookup(...)`!
+
+Whether this entry was loaded from the cache or came from a query (`cache` or `query`)
+
 ### Entry object (callback-style)
 
 When `options.all` is `false`, then `callback(error, address, family, expires, ttl)` is called. <br>

index.d.ts

@@ -4,6 +4,7 @@ import {Agent} from 'http';
 type AsyncResolver = dnsPromises.Resolver;
 
 export type IPFamily = 4 | 6;
+export type EntrySource = 'query' | 'cache';
 
 type TPromise<T> = T | Promise<T>;
 
@@ -72,6 +73,10 @@ export interface EntryObject {
 	 * The expiration timestamp.
 	 */
 	readonly expires?: number;
+	/**
+	 * Whether this entry comes from the cache or a query
+	 */
+	readonly source?: EntrySource;
 }
 
 export interface LookupOptions {

source/index.js

@@ -160,7 +160,7 @@ class CacheableLookup {
 			if (options.all) {
 				callback(null, result);
 			} else {
-				callback(null, result.address, result.family, result.expires, result.ttl);
+				callback(null, result.address, result.family, result.expires, result.ttl, result.source);
 			}
 		}, callback);
 	}
@@ -211,6 +211,7 @@ class CacheableLookup {
 	}
 
 	async query(hostname) {
+		let source = 'cache';
 		let cached = await this._cache.get(hostname);
 
 		if (!cached) {
@@ -219,6 +220,7 @@ class CacheableLookup {
 			if (pending) {
 				cached = await pending;
 			} else {
+				source = 'query';
 				const newPromise = this.queryAndCache(hostname);
 				this._pending[hostname] = newPromise;
 
@@ -231,7 +233,7 @@ class CacheableLookup {
 		}
 
 		cached = cached.map(entry => {
-			return {...entry};
+			return {...entry, source};
 		});
 
 		return cached;

tests/test.js

@@ -237,6 +237,7 @@ const verify = (t, entry, value) => {
 		for (const key in value) {
 			t.true(typeof entry[key].expires === 'number' && entry[key].expires >= Date.now() - 1000);
 			t.true(typeof entry[key].ttl === 'number' && entry[key].ttl >= 0);
+			t.true(['cache', 'query'].includes(entry[key].source));
 
 			if (!('ttl' in value[key]) && 'ttl' in entry[key]) {
 				value[key].ttl = entry[key].ttl;
@@ -245,10 +246,15 @@ const verify = (t, entry, value) => {
 			if (!('expires' in value[key]) && 'expires' in entry[key]) {
 				value[key].expires = entry[key].expires;
 			}
+
+			if (!('source' in value[key]) && 'source' in entry[key]) {
+				value[key].source = entry[key].source;
+			}
 		}
 	} else {
 		t.true(typeof entry.expires === 'number' && entry.expires >= Date.now() - 1000);
 		t.true(typeof entry.ttl === 'number' && entry.ttl >= 0);
+		t.true(['cache', 'query'].includes(entry.source));
 
 		if (!('ttl' in value)) {
 			value.ttl = entry.ttl;
@@ -257,6 +263,10 @@ const verify = (t, entry, value) => {
 		if (!('expires' in value)) {
 			value.expires = entry.expires;
 		}
+
+		if (!('source' in value)) {
+			value.source = entry.source;
+		}
 	}
 
 	t.deepEqual(entry, value);
@@ -401,18 +411,18 @@ test.serial('caching works', async t => {
 	// Make sure default behavior is right
 	let entries = await cacheable.lookupAsync('temporary', {all: true, family: 4});
 	verify(t, entries, [
-		{address: '127.0.0.1', family: 4}
+		{address: '127.0.0.1', family: 4, source: 'query'}
 	]);
 
 	// Update DNS data
 	const resovlerEntry = resolver.data['127.0.0.1'].temporary[0];
 	const {address: resolverAddress} = resovlerEntry;
 	resovlerEntry.address = '127.0.0.2';
 
-	// Lookup again
+	// Lookup again returns cached data
 	entries = await cacheable.lookupAsync('temporary', {all: true, family: 4});
 	verify(t, entries, [
-		{address: '127.0.0.1', family: 4}
+		{address: '127.0.0.1', family: 4, source: 'cache'}
 	]);
 
 	// Restore back
@@ -486,7 +496,7 @@ test('callback style', async t => {
 
 	// Without options
 	let result = await lookup('localhost');
-	t.is(result.length, 4);
+	t.is(result.length, 5);
 	t.is(result[0], '127.0.0.1');
 	t.is(result[1], 4);
 	t.true(typeof result[2] === 'number' && result[2] >= Date.now() - 1000);
@@ -1038,7 +1048,8 @@ test('slow dns.lookup', async t => {
 
 	t.deepEqual(entry, {
 		address: '127.0.0.1',
-		family: 4
+		family: 4,
+		source: 'query'
 	});
 });