Merge pull request #57 from PolymerElements/precache-hash

Use precacheHash in the config file in lieu of a precache URL param

bootstrap/sw-toolbox-setup.js

@@ -21,10 +21,28 @@
     var strategy = global.params.get('defaultCacheStrategy');
     global.toolbox.router.default = global.toolbox[strategy] || global[strategy];
   }
-
-  if (global.params.has('precache')) {
-    global.toolbox.precache(global.params.get('precache'));
+
+  var precachePromise;
+  // When precacheFingerprint is present inside the cacheConfigFile JSON, its a signal that instead
+  // of reading the list of URLs to precache from the service worker's URL parameters, we need to
+  // instead fetch the JSON file and read the list of precache URLs for there. This works around
+  // the problem that the list of URLs to precache might be longer than the browser-specific limit
+  // on the size of a service worker's URL.
+  if (global.params.has('precacheFingerprint') && global.params.has('cacheConfigFile')) {
+    precachePromise = global.fetch(global.params.get('cacheConfigFile')).then(function(response) {
+      return response.json();
+    }).then(function(json) {
+      return json.precache || [];
+    }).catch(function(error) {
+      return [];
+    }).then(function(precache) {
+      return precache.concat(global.params.get('precache'));
+    })
+  } else {
+    precachePromise = Promise.resolve(global.params.get('precache'));
   }
+
+  global.toolbox.precache(precachePromise);
 
   if (global.params.has('route')) {
     var setsOfRouteParams = global.params.get('route');

bower.json

@@ -26,7 +26,7 @@
   ],
   "dependencies": {
     "polymer": "Polymer/polymer#^1.0.0",
-    "sw-toolbox": "^2.0.2"
+    "sw-toolbox": "^2.0.4"
   },
   "devDependencies": {
     "iron-component-page": "PolymerElements/iron-component-page#^1.0.2",

platinum-sw-cache.html

@@ -45,13 +45,33 @@
        * be concatenated with the values in the JSON file's `precache` property and the set of files
        * that are precached will be the union of the two.
        *
+       * There's one additional option, `precacheFingerprint`, that can be set in the JSON. If using
+       * a build script that might output a large number of files to precache, its recommended
+       * that your build script generate a unique "fingerprint" of the files. Any changes to the
+       * `precacheFingerprint` value will result in the underlying service worker kicking off the
+       * process of caching the files listed in `precache`.
+       * While there are a few different strategies for generating an appropriate
+       * `precacheFingerprint` value, a process that makes sense is to use a stable hash of the
+       * serialized `precache` array. That way, any changes to the list of files in `precache`
+       * will result in a new `precacheFingerprint` value.
+       * If your build script is Node.js based, one way to generate this hash is:
+       *
+       *     var md5 = require('crypto').createHash('md5');
+       *     md5.update(JSON.stringify(precache));
+       *     var precacheFingerprint = md5.digest('hex');
+       *
+       * Alternatively, you could use something like the
+       * [SHA-1 signature](http://stackoverflow.com/questions/1161869/how-to-get-sha-of-the-latest-commit-from-remote-git-repository)
+       * of your latest `git` commit for the `precacheFingerprint` value.
+       *
        * An example file may look like:
        *
        *     {
        *       "cacheId": "my-cache-id",
        *       "defaultCacheStrategy": "fastest",
        *       "disabled": false,
-       *       "precache": ["file1.html", "file2.css"]
+       *       "precache": ["file1.html", "file2.css"],
+       *       "precacheFingerprint": "FINGERPRINT_OF_FILES_IN_PRECACHE"
        *     }
        */
       cacheConfigFile: String,
@@ -62,7 +82,7 @@
        * in which all the resources will be stored.
        *
        * If nothing is provided, the default value set in
-       * [`sw-toolbox.options.cacheName`](https://github.com/GoogleChrome/sw-toolbox/blob/8763dcc9fbc9352d58f184050e2131c42f7b6d68/lib/options.js#L28)
+       * [`toolbox.options.cacheName`](https://github.com/GoogleChrome/sw-toolbox/blob/8763dcc9fbc9352d58f184050e2131c42f7b6d68/lib/options.js#L28)
        * will be used.
        *
        * The `cacheId` is combined with the service worker's scope to construct the cache name, so
@@ -126,6 +146,7 @@
         };
 
         if (this.cacheConfigFile) {
+          params.cacheConfigFile = this.cacheConfigFile;
           window.fetch(this.cacheConfigFile).then(function(response) {
             if (!response.ok) {
               throw Error('unable to load ' + this.cacheConfigFile);
@@ -137,7 +158,18 @@
               // Use an empty set of parameters to effectively disable caching.
               params = {};
             } else {
-              params.precache = params.precache.concat(config.precache);
+              // If there's a hash of the list of files to precache provided in the config file,
+              // then copy that over to the params that will be used to construct the service worker
+              // URL. This works around the issue where a potentially large number of precache
+              // files could result in a longer URL than a browser will allow.
+              // The actual list of files to precache (in config.precache) will be dealt by the
+              // service worker during the install phase, so we can ignore it here.
+              // See https://github.com/PolymerElements/platinum-sw/issues/53
+              if (config.precacheFingerprint) {
+                params.precacheFingerprint = config.precacheFingerprint;
+              } else {
+                params.precache = params.precache.concat(config.precache);
+              }
               params.cacheId = config.cacheId || params.cacheId;
               params.defaultCacheStrategy = config.defaultCacheStrategy ||
                 params.defaultCacheStrategy;

test/platinum-sw-cache/cache-config.json

@@ -2,5 +2,6 @@
   "cacheId": "my-cache-id",
   "defaultCacheStrategy": "networkOnly",
   "disabled": false,
-  "precache": ["listed_in_json1.txt", "listed_in_json2.txt"]
+  "precache": ["listed_in_json1.txt", "listed_in_json2.txt"],
+  "precacheFingerprint": "DUMMY_HASH"
 }

test/platinum-sw-cache/index.html

@@ -33,7 +33,7 @@
         suite('Precaching', function() {
           test('precache results in Cache Storage API entries', function() {
             return navigator.serviceWorker.ready.then(function() {
-              window.fetch(swc.cacheConfigFile).then(function(response) {
+              return window.fetch(swc.cacheConfigFile).then(function(response) {
                 return response.json();
               }).then(function(config) {
                 return swc.precache.concat(config.precache);