core(simulator): add DNS timing (#5607)

lighthouse-core/gather/computed/metrics/lantern-first-contentful-paint.js

@@ -20,8 +20,8 @@ class FirstContentfulPaint extends MetricArtifact {
    */
   get COEFFICIENTS() {
     return {
-      intercept: 600,
-      optimistic: 0.6,
+      intercept: 0,
+      optimistic: 0.5,
       pessimistic: 0.5,
     };
   }

lighthouse-core/gather/computed/metrics/lantern-first-cpu-idle.js

@@ -14,6 +14,18 @@ class LanternFirstCPUIdle extends LanternInteractive {
     return 'LanternFirstCPUIdle';
   }
 
+  /**
+   * @return {LH.Gatherer.Simulation.MetricCoefficients}
+   */
+  get COEFFICIENTS() {
+    return {
+      intercept: 0,
+      optimistic: 1,
+      pessimistic: 0,
+    };
+  }
+
+
   /**
    * @param {LH.Gatherer.Simulation.Result} simulation
    * @param {Object} extras

lighthouse-core/gather/computed/metrics/lantern-first-meaningful-paint.js

@@ -20,9 +20,9 @@ class FirstMeaningfulPaint extends MetricArtifact {
    */
   get COEFFICIENTS() {
     return {
-      intercept: 900,
-      optimistic: 0.45,
-      pessimistic: 0.6,
+      intercept: 0,
+      optimistic: 0.5,
+      pessimistic: 0.5,
     };
   }
 

lighthouse-core/gather/computed/metrics/lantern-interactive.js

@@ -24,9 +24,9 @@ class Interactive extends MetricArtifact {
    */
   get COEFFICIENTS() {
     return {
-      intercept: 1600,
-      optimistic: 0.6,
-      pessimistic: 0.45,
+      intercept: 0,
+      optimistic: 0.5,
+      pessimistic: 0.5,
     };
   }
 

lighthouse-core/lib/dependency-graph/simulator/dns-cache.js

@@ -0,0 +1,83 @@
+/**
+ * @license Copyright 2018 Google Inc. All Rights Reserved.
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.
+ */
+'use strict';
+
+// A DNS lookup will usually take ~1-2 roundtrips of connection latency plus the extra DNS routing time.
+// Example: https://www.webpagetest.org/result/180703_3A_e33ec79747c002ed4d7bcbfc81462203/1/details/#waterfall_view_step1
+// Example: https://www.webpagetest.org/result/180707_1M_89673eb633b5d98386de95dfcf9b33d5/1/details/#waterfall_view_step1
+// DNS is highly variable though, many times it's a little more than 1, but can easily be 4-5x RTT.
+// We'll use 2 since it seems to give the most accurate results on average, but this can be tweaked.
+const DNS_RESOLUTION_RTT_MULTIPLIER = 2;
+
+class DNSCache {
+  /**
+   * @param {{rtt: number}} options
+   */
+  constructor(options) {
+    this._options = Object.assign(
+      {
+        rtt: undefined,
+      },
+      options
+    );
+
+    if (!this._options.rtt) {
+      throw new Error('Cannot create DNS cache with no rtt');
+    }
+
+    this._rtt = this._options.rtt;
+    /** @type {Map<string, {resolvedAt: number}>} */
+    this._resolvedDomainNames = new Map();
+  }
+
+  /**
+   * @param {LH.Artifacts.NetworkRequest} request
+   * @param {{requestedAt: number, shouldUpdateCache: boolean}=} options
+   * @return {number}
+   */
+  getTimeUntilResolution(request, options) {
+    const {requestedAt = 0, shouldUpdateCache = false} = options || {};
+
+    const domain = request.parsedURL.host;
+    const cacheEntry = this._resolvedDomainNames.get(domain);
+    let timeUntilResolved = this._rtt * DNSCache.RTT_MULTIPLIER;
+    if (cacheEntry) {
+      const timeUntilCachedIsResolved = Math.max(cacheEntry.resolvedAt - requestedAt, 0);
+      timeUntilResolved = Math.min(timeUntilCachedIsResolved, timeUntilResolved);
+    }
+
+    const resolvedAt = requestedAt + timeUntilResolved;
+    if (shouldUpdateCache) this._updateCacheResolvedAtIfNeeded(request, resolvedAt);
+
+    return timeUntilResolved;
+  }
+
+  /**
+   * @param {LH.Artifacts.NetworkRequest} request
+   * @param {number} resolvedAt
+   */
+  _updateCacheResolvedAtIfNeeded(request, resolvedAt) {
+    const domain = request.parsedURL.host;
+    const cacheEntry = this._resolvedDomainNames.get(domain) || {resolvedAt};
+    cacheEntry.resolvedAt = Math.min(cacheEntry.resolvedAt, resolvedAt);
+    this._resolvedDomainNames.set(domain, cacheEntry);
+  }
+
+  /**
+   * Forcefully sets the DNS resolution time for a record.
+   * Useful for testing and alternate execution simulations.
+   *
+   * @param {string} domain
+   * @param {number} resolvedAt
+   */
+  setResolvedAt(domain, resolvedAt) {
+    this._resolvedDomainNames.set(domain, {resolvedAt});
+  }
+}
+
+DNSCache.RTT_MULTIPLIER = DNS_RESOLUTION_RTT_MULTIPLIER;
+
+module.exports = DNSCache;

lighthouse-core/lib/dependency-graph/simulator/simulator.js

@@ -8,6 +8,7 @@
 const BaseNode = require('../base-node');
 const TcpConnection = require('./tcp-connection');
 const ConnectionPool = require('./connection-pool');
+const DNSCache = require('./dns-cache');
 const mobile3G = require('../../../config/constants').throttling.mobile3G;
 
 /** @typedef {BaseNode.Node} Node */
@@ -66,6 +67,7 @@ class Simulator {
     /** @type {Map<string, number>} */
     this._numberInProgressByType = new Map();
     this._nodes = {};
+    this._dns = new DNSCache({rtt: this._rtt});
     // @ts-ignore
     this._connectionPool = /** @type {ConnectionPool} */ (null);
   }
@@ -260,20 +262,26 @@ class Simulator {
    * @return {number}
    */
   _estimateNetworkTimeRemaining(networkNode) {
+    const record = networkNode.record;
     const timingData = this._getTimingData(networkNode);
 
     let timeElapsed = 0;
     if (networkNode.fromDiskCache) {
-      // Rough access time for seeking to location on disk and reading sequentially
+      // Rough access time for seeking to location on disk and reading sequentially = 8ms + 20ms/MB
       // @see http://norvig.com/21-days.html#answers
-      const sizeInMb = (networkNode.record.resourceSize || 0) / 1024 / 1024;
+      const sizeInMb = (record.resourceSize || 0) / 1024 / 1024;
       timeElapsed = 8 + 20 * sizeInMb - timingData.timeElapsed;
     } else {
       // If we're estimating time remaining, we already acquired a connection for this record, definitely non-null
-      const connection = /** @type {TcpConnection} */ (this._acquireConnection(networkNode.record));
+      const connection = /** @type {TcpConnection} */ (this._acquireConnection(record));
+      const dnsResolutionTime = this._dns.getTimeUntilResolution(record, {
+        requestedAt: timingData.startTime,
+        shouldUpdateCache: true,
+      });
+      const timeAlreadyElapsed = timingData.timeElapsed;
       const calculation = connection.simulateDownloadUntil(
-        networkNode.record.transferSize - timingData.bytesDownloaded,
-        {timeAlreadyElapsed: timingData.timeElapsed, maximumTimeToElapse: Infinity}
+        record.transferSize - timingData.bytesDownloaded,
+        {timeAlreadyElapsed, dnsResolutionTime, maximumTimeToElapse: Infinity}
       );
 
       timeElapsed = calculation.timeElapsed;
@@ -318,9 +326,14 @@ class Simulator {
     const record = node.record;
     // If we're updating the progress, we already acquired a connection for this record, definitely non-null
     const connection = /** @type {TcpConnection} */ (this._acquireConnection(record));
+    const dnsResolutionTime = this._dns.getTimeUntilResolution(record, {
+      requestedAt: timingData.startTime,
+      shouldUpdateCache: true,
+    });
     const calculation = connection.simulateDownloadUntil(
       record.transferSize - timingData.bytesDownloaded,
       {
+        dnsResolutionTime,
         timeAlreadyElapsed: timingData.timeElapsed,
         maximumTimeToElapse: timePeriodLength - timingData.timeElapsedOvershoot,
       }
@@ -386,6 +399,7 @@ class Simulator {
 
     // initialize the necessary data containers
     this._flexibleOrdering = !!options.flexibleOrdering;
+    this._dns = new DNSCache({rtt: this._rtt});
     this._initializeConnectionPool(graph);
     this._initializeAuxiliaryData();
 

lighthouse-core/lib/dependency-graph/simulator/tcp-connection.js

@@ -121,7 +121,8 @@ class TcpConnection {
    * @return {DownloadResults}
    */
   simulateDownloadUntil(bytesToDownload, options) {
-    const {timeAlreadyElapsed = 0, maximumTimeToElapse = Infinity} = options || {};
+    const {timeAlreadyElapsed = 0, maximumTimeToElapse = Infinity, dnsResolutionTime = 0} =
+      options || {};
 
     if (this._warmed && this._h2) {
       bytesToDownload -= this._h2OverflowBytesDownloaded;
@@ -133,6 +134,8 @@ class TcpConnection {
     let handshakeAndRequest = oneWayLatency;
     if (!this._warmed) {
       handshakeAndRequest =
+        // DNS lookup
+        dnsResolutionTime +
         // SYN
         oneWayLatency +
         // SYN ACK
@@ -188,6 +191,7 @@ module.exports = TcpConnection;
 
 /**
  * @typedef DownloadOptions
+ * @property {number} [dnsResolutionTime]
  * @property {number} [timeAlreadyElapsed]
  * @property {number} [maximumTimeToElapse]
  */

lighthouse-core/test/audits/__snapshots__/load-fast-enough-for-pwa-test.js.snap

@@ -0,0 +1,3 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`PWA: load-fast-enough-for-pwa audit overrides with simulated result when throttling is modified 1`] = `3427`;

lighthouse-core/test/audits/__snapshots__/metrics-test.js.snap

@@ -0,0 +1,38 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`Performance: metrics evaluates valid input correctly 1`] = `
+Object {
+  "estimatedInputLatency": 104,
+  "estimatedInputLatencyTs": undefined,
+  "firstCPUIdle": 3351,
+  "firstCPUIdleTs": undefined,
+  "firstContentfulPaint": 911,
+  "firstContentfulPaintTs": undefined,
+  "firstMeaningfulPaint": 1355,
+  "firstMeaningfulPaintTs": undefined,
+  "interactive": 3427,
+  "interactiveTs": undefined,
+  "observedDomContentLoaded": 560,
+  "observedDomContentLoadedTs": 225414732309,
+  "observedFirstContentfulPaint": 499,
+  "observedFirstContentfulPaintTs": 225414670885,
+  "observedFirstMeaningfulPaint": 783,
+  "observedFirstMeaningfulPaintTs": 225414955343,
+  "observedFirstPaint": 499,
+  "observedFirstPaintTs": 225414670868,
+  "observedFirstVisualChange": 520,
+  "observedFirstVisualChangeTs": 225414692015,
+  "observedLastVisualChange": 818,
+  "observedLastVisualChangeTs": 225414990015,
+  "observedLoad": 2199,
+  "observedLoadTs": 225416370913,
+  "observedNavigationStart": 0,
+  "observedNavigationStartTs": 225414172015,
+  "observedSpeedIndex": 605,
+  "observedSpeedIndexTs": 225414776724,
+  "observedTraceEnd": 12540,
+  "observedTraceEndTs": 225426711887,
+  "speedIndex": 1656,
+  "speedIndexTs": undefined,
+}
+`;

lighthouse-core/test/audits/__snapshots__/predictive-perf-test.js.snap

@@ -0,0 +1,24 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`Performance: predictive performance audit should compute the predicted values 1`] = `
+Object {
+  "optimisticEIL": 101,
+  "optimisticFCP": 911,
+  "optimisticFMP": 1211,
+  "optimisticSI": 605,
+  "optimisticTTFCPUI": 3351,
+  "optimisticTTI": 3351,
+  "pessimisticEIL": 158,
+  "pessimisticFCP": 911,
+  "pessimisticFMP": 1498,
+  "pessimisticSI": 1630,
+  "pessimisticTTFCPUI": 3502,
+  "pessimisticTTI": 3502,
+  "roughEstimateOfEIL": 104,
+  "roughEstimateOfFCP": 911,
+  "roughEstimateOfFMP": 1355,
+  "roughEstimateOfSI": 1656,
+  "roughEstimateOfTTFCPUI": 3351,
+  "roughEstimateOfTTI": 3427,
+}
+`;

lighthouse-core/test/audits/byte-efficiency/__snapshots__/byte-efficiency-audit-test.js.snap

@@ -0,0 +1,12 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`Byte efficiency base audit should allow overriding of computeWasteWithTTIGraph 1`] = `
+Object {
+  "default": 1330,
+  "justTTI": 950,
+}
+`;
+
+exports[`Byte efficiency base audit should create load simulator with the specified settings 1`] = `1330`;
+
+exports[`Byte efficiency base audit should create load simulator with the specified settings 2`] = `22950`;

lighthouse-core/test/audits/byte-efficiency/byte-efficiency-audit-test.js

@@ -218,12 +218,14 @@ describe('Byte efficiency base audit', () => {
     let settings = {throttlingMethod: 'simulate', throttling: modestThrottling};
     let result = await MockAudit.audit(artifacts, {settings});
     // expect modest savings
-    assert.equal(result.rawValue, 1480);
+    expect(result.rawValue).toBeLessThan(5000);
+    expect(result.rawValue).toMatchSnapshot();
 
     settings = {throttlingMethod: 'simulate', throttling: ultraSlowThrottling};
     result = await MockAudit.audit(artifacts, {settings});
     // expect lots of savings
-    assert.equal(result.rawValue, 22350);
+    expect(result.rawValue).not.toBeLessThan(5000);
+    expect(result.rawValue).toMatchSnapshot();
   });
 
   it('should allow overriding of computeWasteWithTTIGraph', async () => {
@@ -251,8 +253,8 @@ describe('Byte efficiency base audit', () => {
     const settings = {throttlingMethod: 'simulate', throttling: modestThrottling};
     const result = await MockAudit.audit(artifacts, {settings});
     const resultTti = await MockJustTTIAudit.audit(artifacts, {settings});
-    // expect more savings from default
-    assert.equal(result.rawValue, 1480);
-    assert.equal(resultTti.rawValue, 800);
+    // expect less savings with just TTI
+    expect(resultTti.rawValue).toBeLessThan(result.rawValue);
+    expect({default: result.rawValue, justTTI: resultTti.rawValue}).toMatchSnapshot();
   });
 });

lighthouse-core/test/audits/byte-efficiency/render-blocking-resources-test.js

@@ -51,7 +51,7 @@ describe('Render blocking resources audit', () => {
     beforeEach(() => {
       requestId = 1;
       record = props => {
-        const parsedURL = {securityOrigin: 'http://example.com'};
+        const parsedURL = {host: 'example.com', securityOrigin: 'http://example.com'};
         return Object.assign({parsedURL, requestId: requestId++}, props);
       };
     });

lighthouse-core/test/audits/load-fast-enough-for-pwa-test.js

@@ -67,6 +67,7 @@ describe('PWA: load-fast-enough-for-pwa audit', () => {
 
     const settings = {throttlingMethod: 'provided', throttling: {rttMs: 40, throughput: 100000}};
     const result = await FastPWAAudit.audit(artifacts, {settings});
-    assert.equal(Math.round(result.rawValue), 4309);
+    expect(result.rawValue).toBeGreaterThan(2000);
+    expect(Math.round(result.rawValue)).toMatchSnapshot();
   });
 });