Added audit for request compression (gzip & br)

lighthouse-core/audits/byte-efficiency/uses-request-compression.js

@@ -0,0 +1,105 @@
+/**
+ * @license
+ * Copyright 2017 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.
+ */
+/*
+ * @fileoverview Audit a page to ensure that resources loaded with
+ * gzip/br/deflate compression.
+ */
+'use strict';
+
+const Audit = require('./byte-efficiency-audit');
+const URL = require('../../lib/url-shim');
+
+const IGNORE_THRESHOLD_IN_BYTES = 1400;
+const IGNORE_THRESHOLD_IN_PERCENT = 0.1;
+const TOTAL_WASTED_BYTES_THRESHOLD = 10 * 1024; // 10KB
+
+class ResponsesAreCompressed extends Audit {
+  /**
+   * @return {!AuditMeta}
+   */
+  static get meta() {
+    return {
+      category: 'Performance',
+      name: 'uses-request-compression',
+      description: 'Compression enabled for server responses',
+      helpText: 'Text-based responses should be served with compression (gzip, deflate or brotli)' +
+        ' to minimize total network bytes.' +
+        ' [Learn more](https://developers.google.com/web/fundamentals/performance/optimizing-content-efficiency/optimize-encoding-and-transfer).',
+      requiredArtifacts: ['ResponseCompression', 'networkRecords']
+    };
+  }
+
+  /**
+   * @param {!Artifacts} artifacts
+   * @param {number} networkThroughput
+   * @return {!AuditResult}
+   */
+  static audit_(artifacts) {
+    const uncompressedResponses = artifacts.ResponseCompression;
+
+    let totalWastedBytes = 0;
+    const results = [];
+    uncompressedResponses.forEach(record => {
+      const originalSize = record.resourceSize;
+      const gzipSize = record.gzipSize;
+      const gzipSavings = originalSize - gzipSize;
+
+      // we require at least 10% savings off the original size AND at least 1400 bytes
+      // if the savings is smaller than either, we don't care
+      if (
+          1 - gzipSize / originalSize < IGNORE_THRESHOLD_IN_PERCENT ||
+          gzipSavings < IGNORE_THRESHOLD_IN_BYTES
+      ) {
+        return;
+      }
+
+      // remove duplicates
+      const url = URL.getDisplayName(record.url);
+      const isDuplicate = results.find(res => res.url === url &&
+        res.totalBytes === record.resourceSize);
+      if (isDuplicate) {
+        return;
+      }
+
+      totalWastedBytes += gzipSavings;
+      const totalBytes = originalSize;
+      const gzipSavingsBytes = gzipSavings;
+      const gzipSavingsPercent = 100 * gzipSavingsBytes / totalBytes;
+      results.push({
+        url,
+        totalBytes,
+        wastedBytes: gzipSavingsBytes,
+        wastedPercent: gzipSavingsPercent,
+        potentialSavings: this.toSavingsString(gzipSavingsBytes, gzipSavingsPercent),
+      });
+    });
+
+    let debugString;
+    return {
+      passes: totalWastedBytes < TOTAL_WASTED_BYTES_THRESHOLD,
+      debugString,
+      results,
+      tableHeadings: {
+        url: 'Uncompressed resource URL',
+        totalKb: 'Original',
+        potentialSavings: 'GZIP Savings',
+      }
+    };
+  }
+}
+
+module.exports = ResponsesAreCompressed;

lighthouse-core/config/default.js

@@ -51,6 +51,7 @@ module.exports = {
       "dobetterweb/notification-on-start",
       "dobetterweb/domstats",
       "dobetterweb/optimized-images",
+      "dobetterweb/response-compression",
       "dobetterweb/tags-blocking-first-paint",
       "dobetterweb/websql"
     ]
@@ -115,6 +116,7 @@ module.exports = {
     // "byte-efficiency/unused-css-rules",
     "byte-efficiency/offscreen-images",
     "byte-efficiency/uses-optimized-images",
+    "byte-efficiency/uses-request-compression",
     "byte-efficiency/uses-responsive-images",
     "dobetterweb/appcache-manifest",
     "dobetterweb/dom-size",
@@ -532,6 +534,10 @@ module.exports = {
           "expectedValue": true,
           "weight": 1
         },
+        "uses-request-compression": {
+          "expectedValue": true,
+          "weight": 1
+        },
         "uses-responsive-images": {
           "expectedValue": true,
           "weight": 1
@@ -614,6 +620,7 @@ module.exports = {
         {"id": "script-blocking-first-paint", "weight": 0},
         // {"id": "unused-css-rules", "weight": 0},
         {"id": "uses-optimized-images", "weight": 0},
+        {"id": "uses-request-compression", "weight": 0},
         {"id": "uses-responsive-images", "weight": 0},
         {"id": "total-byte-weight", "weight": 0},
         {"id": "dom-size", "weight": 0},