title: Angular service worker swUpdate checkForUpdate() / available Observable
body: <p>Angular: v8.x</p>
  <p>Ionic: v5.x</p>
  <p>Currently, I have configured my ngsw-config.json as follows:</p>
  <pre><code>{
    &quot;$schema&quot;: &quot;./node_modules/@angular/service-worker/config/schema.json&quot;,
    &quot;index&quot;: &quot;/index.html&quot;,
    &quot;assetGroups&quot;: [
      {
        &quot;name&quot;: &quot;app&quot;,
        &quot;installMode&quot;: &quot;prefetch&quot;,
        &quot;resources&quot;: {
          &quot;files&quot;: [
            &quot;/favicon.ico&quot;,
            &quot;/index.html&quot;,
            &quot;/manifest.webmanifest&quot;,
            &quot;/*.css&quot;,
            &quot;/*.js&quot;
          ]
        }
      }, {
        &quot;name&quot;: &quot;assets&quot;,
        &quot;installMode&quot;: &quot;lazy&quot;,
        &quot;updateMode&quot;: &quot;prefetch&quot;,
        &quot;resources&quot;: {
          &quot;files&quot;: [
            &quot;/assets/**&quot;,
            &quot;/*.(eot|svg|cur|jpg|png|webp|gif|otf|ttf|woff|woff2|ani)&quot;
          ]
        }
      }
    ],
    &quot;dataGroups&quot;: [
      {
        &quot;name&quot;: &quot;api_data&quot;,
        &quot;urls&quot;: [
          &quot;**/api/**&quot;
        ],
        &quot;cacheConfig&quot;: {
          &quot;strategy&quot;: &quot;freshness&quot;,
          &quot;timeout&quot;: &quot;3s&quot;,
          &quot;maxAge&quot;: &quot;7d&quot;,
          &quot;maxSize&quot;: 50
        }
      }
      
  
    ]
  }
  
  </code></pre>
  <p>Data groups strategy is set to <code>freshness</code> so on a second * full reload I see the updated data in my app.</p>
  <p>However I've noticed that</p>
  <p><code>this.swUpdate.checkForUpdate()</code> or <code>this.swUpdate.available()</code> do nothing.</p>
  <p>No observable event is fired by swUpdate when the service worker gets data for the first time (freshness).</p>
  <p>** Note on second full reload the cache data is anyways updated and the user see's the updated app.</p>
  <p>Does swUpdate not trigger for updates in dataGroups (only for assetGroups) cache?</p>