PERF: Have nginx cache and serve the service worker file.

app/assets/javascripts/discourse/initializers/register-service-worker.js.es6

@@ -2,27 +2,27 @@ export default {
   name: 'register-service-worker',
 
   initialize() {
-    // only allow service worker on android for now
-    if (!/(android)/i.test(navigator.userAgent)) {
+    window.addEventListener('load', () => {
+      const isSecured = (document.location.protocol === 'https:') ||
+        (location.hostname === "localhost");
 
-      // remove old service worker
-      if ('serviceWorker' in navigator && navigator.serviceWorker.getRegistrations) {
-        navigator.serviceWorker.getRegistrations().then((registrations) => {
+      const isSupported= isSecured && ('serviceWorker' in navigator);
+
+      if (isSupported) {
+        if (Discourse.ServiceWorkerURL) {
+          navigator.serviceWorker
+            .register(`${Discourse.BaseUri}/${Discourse.ServiceWorkerURL}`)
+            .catch(error => {
+              Ember.Logger.info(`Failed to register Service Worker: ${error}`);
+            });
+        } else {
+          navigator.serviceWorker.getRegistrations().then(registrations => {
             for(let registration of registrations) {
               registration.unregister();
             };
           });
         }
-
-    } else {
-
-      const isSecure = (document.location.protocol === 'https:') ||
-        (location.hostname === "localhost");
-
-
-      if (isSecure && ('serviceWorker' in navigator)) {
-        navigator.serviceWorker.register(`${Discourse.BaseUri}/service-worker.js`);
-      }
       }
+    });
   }
 };

app/controllers/static_controller.rb

@@ -148,9 +148,9 @@ class StaticController < ApplicationController
   def service_worker_asset
     respond_to do |format|
       format.js do
-
-        # we take 1 hour to give a new service worker to all users
-        immutable_for 1.hour
+        # https://github.com/w3c/ServiceWorker/blob/master/explainer.md#updating-a-service-worker
+        # Maximum cache that the service worker will respect is 24 hours.
+        immutable_for 24.hours
 
         render(
           plain: Rails.application.assets_manifest.find_sources('service-worker.js').first,

app/views/common/_discourse_javascript.html.erb

@@ -44,6 +44,9 @@
     Discourse.SiteSettings = ps.get('siteSettings');
     Discourse.LetterAvatarVersion = '<%= LetterAvatar.version %>';
     Discourse.MarkdownItURL = '<%= asset_url('markdown-it-bundle.js') %>';
+    <%- if DiscoursePluginRegistry.service_workers.present? %>
+    Discourse.ServiceWorkerURL = '<%= Rails.application.assets_manifest.assets['service-worker.js'] %>'
+    <%- end %>
     I18n.defaultLocale = '<%= SiteSetting.default_locale %>';
     Discourse.start();
     Discourse.set('assetVersion','<%= Discourse.assets_digest %>');

config/nginx.sample.conf

@@ -188,7 +188,7 @@ server {
     # This big block is needed so we can selectively enable
     # acceleration for backups and avatars
     # see note about repetition above
-    location ~ ^/(letter_avatar/|user_avatar|highlight-js|stylesheets|favicon/proxied) {
+    location ~ ^/(letter_avatar/|user_avatar|highlight-js|stylesheets|favicon/proxied|service-worker-.*.js) {
       proxy_set_header Host $http_host;
       proxy_set_header X-Real-IP $remote_addr;
       proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;

config/routes.rb

@@ -696,7 +696,9 @@ Discourse::Application.routes.draw do
   post "draft" => "draft#update"
   delete "draft" => "draft#destroy"
 
-  get "service-worker" => "static#service_worker_asset", format: :js
+  if service_worker_asset = Rails.application.assets_manifest.assets['service-worker.js']
+    get service_worker_asset => "static#service_worker_asset", format: :js
+  end
 
   get "cdn_asset/:site/*path" => "static#cdn_asset", format: false
   get "brotli_asset/*path" => "static#brotli_asset", format: false