Service Worker Registered and Activated but Doesn't Work in Offline Mode

Question

In a UI5 application, I've registered my service worker in index.html :

$(document).ready(function() {
  if ('serviceWorker' in navigator) {
    navigator.serviceWorker
      .register('service-worker.js', { scope: './' })
      .then(function(registration) {
        console.log("Service Worker Registered");
      })
      .catch(function(err) {
        console.log("Service Worker Failed to Register", err);
      })
  }
});

Also, I have the file service-worker.js in the root folder so that the service worker can cache all the elements below it. This file contains the following code:

// Set a name for the current cache
var cacheName = 'v2'; 

// Default files to always cache
var cacheFiles = [
    './',
    './inicio.html?I_APLICACION=CAPCGENA02',
    './resources/sap-ui-core.js',
    './resources/sap/ui/core/themes/base/fonts/SAP-icons.ttf',
    './resources/sap-ui-core.js',
    './resources/sap/ui/core/library-preload.js',
    './resources/sap/m/library-preload.js',
    './resources/sap/ui/unified/library-preload.js',
    './resources/sap/ui/comp/library-preload.js',
    './resources/sap/ui/table/library-preload.js',
    './resources/sap/ui/fl/library-preload.js',
    './resources/sap/tnt/library-preload.js',
    './resources/sap/ui/unified/themes/sap_belize/library-parameters.json',
    './resources/sap/ui/table/themes/sap_belize/library-parameters.json',
    './resources/sap/ui/comp/themes/sap_belize/library-parameters.json',
    './resources/sap/tnt/themes/sap_belize/library-parameters.json',
    './resources/sap/ui/layout/library-preload.js',
    './resources/sap/ui/unified/themes/sap_belize/library.css',
    './resources/sap/ui/table/themes/sap_belize/library.css',
    './resources/sap/ui/comp/themes/sap_belize/library.css',
    './resources/sap/tnt/themes/sap_belize/library.css',
    './css/style.css',
    './css/fonts/ttf/CMEEMEN18.ttf',
    './images/temporal/chart.PNG',
    './Component.js',
    './Component-preload.js',
    './manifest.json',
    './api/api.reformation.data.js',
    './api/ApiManager.js',
    './api/ApiStructure.js',
    './api/ibd.api.login.data.js',
    './controller/Home.controller.js',
    './controller/Login.controller.js',
    './controller/Menu.controller.js',
    './controller/fragment/ManagePartes.js',
    './controller/fragment/FilterDialogController.js',
    './controller/structure/Container.controller.js',
    './controller/structur
    './database/apiBBDD.js',
    './database/bbdd.js',
    './i18n/i18n.properties',
    './i18n/i18n_en.properties',
    './i18n/i18n_es.properties',
    './i18n/i18n_en_US.properties',
    './i18n/i18n_es_ES.properties',
    './manager/dataManager/DataManager.js',
    './manager/functionalityManager/FunctionalityManager.js',
    './manager/mappingManager/MappingManager.js',
    './manager/parserManager/ReformationParser.js',
    './manager/sessionManager/SessionManager.js',
    './manager/structureManager/ElementManager.js',
    './manager/structureManager/StructureManager.js',
    './manager/viewManager/ViewManager.js',
    './singleton/Singleton.js',
    './utils/Consts.js',
    './utils/Funcionality.js',
    './utils/FunctionalityEvent.js',
    './utils/MaskedPassword.js',
    './utils/Utils.js',
    './view/Home.view.xml',
    './view/Login.view.xml',
    './view/Menu.view.xml',
    './view/fragment/DialogConfirm.fragment.xml',
    './view/fragment/DialogEnd.fragment.xml',
    './view/fragment/DialogError.fragment.xml',
    './view/fragment/DialogTag.fragment.xml',
    './view/fragment/DialogWaiting.fragment.xml',
    './view/fragment/HistoryDialog.fragment.xml',
    './view/fragment/HistoryNoticeDialog.fragment.xml',

]


self.addEventListener('install', function(e) {
    console.log('[ServiceWorker] Installed');

    // e.waitUntil Delays the event until the Promise is resolved
    e.waitUntil(

        // Open the cache
        caches.open(cacheName).then(function(cache) {

            // Add all the default files to the cache
            console.log('[ServiceWorker] Caching cacheFiles');
            //return cache.addAll(cacheFiles);
            return cache.addAll(cacheFiles.map(url => new Request(url, {credentials: 'same-origin'})));
        })
    ); // end e.waitUntil
});


self.addEventListener('activate', function(e) {
    console.log('[ServiceWorker] Activated');

    e.waitUntil(

        // Get all the cache keys (cacheName)
        caches.keys().then(function(cacheNames) {
            return Promise.all(cacheNames.map(function(thisCacheName) {

                // If a cached item is saved under a previous cacheName
                if (thisCacheName !== cacheName) {

                    // Delete that cached file
                    console.log('[ServiceWorker] Removing Cached Files from Cache - ', thisCacheName);
                    return caches.delete(thisCacheName);
                }
            }));
        })
    ); // end e.waitUntil

});


self.addEventListener('fetch', function(e) {
    console.log('[ServiceWorker] Fetch', e.request.url);

    // e.respondWidth Responds to the fetch event
    e.respondWith(

        // Check in cache for the request being made
        caches.match(e.request)


            .then(function(response) {

                // If the request is in the cache
                if ( response ) {
                    console.log("[ServiceWorker] Found in Cache", e.request.url, response);
                    // Return the cached version
                    return response;
                }

                // If the request is NOT in the cache, fetch and cache

                var requestClone = e.request.clone();
                fetch(requestClone)
                    .then(function(response) {

                        if ( !response ) {
                            console.log("[ServiceWorker] No response from fetch ")
                            return response;
                        }

                        var responseClone = response.clone();

                        //  Open the cache
                        caches.open(cacheName).then(function(cache) {

                            // Put the fetched response in the cache
                            cache.put(e.request, responseClone);
                            console.log('[ServiceWorker] New Data Cached', e.request.url);

                            // Return the response
                            return response;

                        }); // end caches.open

                    })
                    .catch(function(err) {
                        console.log('[ServiceWorker] Error Fetching & Caching New Data', err);
                    });


            }) // end caches.match(e.request)
    ); // end e.respondWith
});

With all this, I get my service worker installed and activated correctly. And if I go to the Cache Storage tab, I have the information cached:

My connection is secure (HTTPS) but when I put in offline mode, the requests come back from cache-disk instead of from service-worker.

I guess it's because it is taking it from the automatic caching of browsers, but if I click on the "Disable cache" option in Chrome, it does not load the offline page.

Does anyone know why this happens?

Answer 1

Here is an answer to "Has anyone worked on Service Worker Implementation in SAPUI5?"
And the quote from MDN :

[Service Worker] is designed to be fully async ; as a consequence, APIs such as synchronous XHR [...] can't be used inside a service worker.

So currently, Service Worker doesn't intercept sync XHRs and UI5 does send many sync XHRs which explains why those files are not intercepted .

Therefore, try to reduce sync XHRs as much as possible as explained in here .

1. Create the Component-Preload file

2. Set everywhere async: true whenever possible. Eg

   • For components

     sap.ui.component({ manifestUrl: "...", async: true, })

   • Root View (in app descriptor)

      rootView : { viewName: "...", type: "XML", async: true, ... },

3. Load libraries asynchronously via the bootstrap config preload with the value "async" . Eg:

    data-sap-ui-preload="async"

4. Preload libraries with enabled xx-waitForTheme . Eg:

    data-sap-ui-libs="sap.m, sap.ui.core, sap.f" data-sap-ui-xx-waitForTheme="true"

I also see you have some fragments . Avoid loading controls lazily via fragment factory since fragments are fetched synchronously by this way.