Compile: Cache the assets in a service worker

The stylesheet, scripts and logo are sent with a year-long expiration but some
hosts forbid caching anything their interface generates - cPanel's cpsrvd sends
no-store - so every page downloaded them again. The Cache Storage is filled by
explicit put() calls, which those headers don't reach.

The worker configures itself from its own ?file=worker.js&version= URL and
touches only the files of that version, leaving everything else, navigations
included, to the browser. It is registered with location.pathname as the scope,
the narrowest one allowed, so it never sees the rest of the origin.

Adminer can be logged in to several connections at once, so the worker is
unregistered - and its caches deleted, which unregistering alone doesn't do -
only once none is left. That is also why the login form doesn't register it
back.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: vrana

CHANGELOG.md

@@ -3,6 +3,7 @@
 - Alter routine: Preserve all characteristics and edit them in a form instead of in the definition
 - Autocomplete: Offer also in the definition of a routine, an event and a view
 - RTL: Mirror the borders, alignment, margins and paddings
+- Cache the assets of the compiled version in a service worker
 - MySQL: Display the check constraint clause without the extra escaping added by information_schema
 - MySQL 9: Create routines with LANGUAGE JAVASCRIPT
 - MS SQL: Get the base type of a column declared with a user-defined type

adminer/file.inc.php

@@ -34,6 +34,9 @@
 ../adminer/static/jush/modules/jush-sqlite.js;
 ../adminer/static/jush/modules/jush-mssql.js;
 ../adminer/static/jush/modules/jush-oracle.js', 'minify_js'));
+} elseif ($_GET["file"] == "worker.js") {
+	header("Content-Type: text/javascript; charset=utf-8");
+	echo decompress_string(compile_file('../adminer/static/worker.js', 'minify_js'));
 } elseif ($_GET["file"] == "logo.png") {
 	header("Content-Type: image/png");
 	echo compile_file('../adminer/static/logo.png');

adminer/include/design.inc.php

@@ -101,6 +101,9 @@ function page_header(string $title, string $error = "", $breadcrumb = array(), s
 	echo "<div id='ajaxstatus' role='status' class='jsonly'></div>\n";
 	restart_session();
 	page_messages($error);
+	if (!defined('Adminer\DIR')) { // only the compiled version serves the files itself, the development version leaves them to the web server
+		service_worker();
+	}
 	$databases = &get_session("dbs");
 	if (DB != "" && $databases && !in_array(DB, $databases, true)) {
 		$databases = null;
@@ -112,6 +115,30 @@ function page_header(string $title, string $error = "", $breadcrumb = array(), s
 	flush();
 }
 
+/** Print the script maintaining the service worker caching the static files */
+function service_worker(): void {
+	$code = (has_passwords() // the worker belongs to all connections at once, so it is removed only after logging out of the last one; the login form must not register it back
+		? "navigator.serviceWorker.register('" . js_escape(preg_replace('~\?.*~', '', ME) . "?file=worker.js&version=" . VERSION) . "', {scope: location.pathname}).catch(() => {});"
+		: "navigator.serviceWorker.getRegistration().then(registration => registration && registration.unregister());
+	caches.keys().then(keys => keys.forEach(key => key.startsWith('adminer-') && caches.delete(key)));"
+	);
+	echo script("if (navigator.serviceWorker) {\n\t$code\n}");
+}
+
+/** Check whether any connection is logged in */
+function has_passwords(): bool {
+	foreach ((array) $_SESSION["pwds"] as $servers) {
+		foreach ($servers as $usernames) {
+			foreach ($usernames as $password) {
+				if ($password !== null) { // logging out sets the password to null, it doesn't remove the key
+					return true;
+				}
+			}
+		}
+	}
+	return false;
+}
+
 /** Send HTTP headers */
 function page_headers(): void {
 	header("Content-Type: text/html; charset=utf-8");

adminer/static/worker.js

@@ -0,0 +1,42 @@
+'use strict';
+
+// Serve the static files of the compiled Adminer from the Cache Storage.
+// The HTTP cache is enough almost everywhere but some hosts forbid caching anything their
+// interface generates, and Adminer generates its own files. Cache Storage is filled by
+// explicit put() calls so those headers don't apply to it.
+
+// this script is served from <Adminer URL>?file=worker.js&version=<version>, the rest follows from that
+const prefix = self.location.href.replace(/worker\.js&version=.*/, '');
+const version = self.location.href.replace(/.*&version=/, '');
+const cacheName = 'adminer-' + version;
+
+// don't wait for the tabs of the previous version to close
+self.addEventListener('install', () => self.skipWaiting());
+
+self.addEventListener('activate', event => {
+	event.waitUntil(self.clients.claim().then(() => caches.keys()).then(keys => Promise.all(
+		keys.filter(key => key != cacheName && key.startsWith('adminer-')).map(key => caches.delete(key))
+	)));
+});
+
+self.addEventListener('fetch', event => {
+	const url = event.request.url;
+	if (
+		event.request.method != 'GET'
+		|| !url.startsWith(prefix)
+		|| !url.endsWith('&version=' + version) // a file of another version, its cache is deleted on activate
+		|| url == self.location.href // the browser fetches this script bypassing this handler but a cached service worker could never be replaced
+	) {
+		return; // not ours - do nothing, which lets the browser handle it as if there was no service worker
+	}
+	event.respondWith(caches.open(cacheName)
+		.then(cache => cache.match(event.request).then(cached => cached || fetch(event.request).then(response => {
+			if (response.ok) {
+				// the version in the URL makes the file immutable so it is never revalidated; waitUntil keeps the worker alive until it is stored
+				event.waitUntil(cache.put(event.request, response.clone()));
+			}
+			return response;
+		})))
+		.catch(() => fetch(event.request)) // a broken cache must not make Adminer unreachable
+	);
+});

docs/developing.md

@@ -403,6 +403,8 @@ The website translations are managed at https://www.adminer.org/en/translations/
 Adminer’s source code is divided into a manageable number of reasonably small files.
 For simpler deployment, these files are bundled into a single `*.php` file by inlining `include` files.
 Static files (`*.js`, `*.css`) are also inlined and served via the `?file=` route.
+They are sent with a year-long expiration but some hosts forbid caching anything their interface generates, so a service worker ([`worker.js`](/adminer/static/worker.js)) keeps them in the Cache Storage, which those headers don't reach.
+It is registered only by the compiled version and unregistered after the last logout.
 
 Includes in Adminer start with `./` to bypass `include_path`, which is unrelated to compilation.