Add extended lifetime shared workers

This PR introduces extended lifetime shared workers as a lightweight alternative to e.g., Service Workers, to perform complex, async operations after document unloading. Specifically, this PR introduces the SharedWorkerOptions dictionary and its extendedLifetime boolean member. Together, they allow a SharedWorkerGlobalScope's lifetime to be extended by an implementation-defined time, when it would otherwise be suspendable.

Before this, a shared worker whose owner set is empty or contains only non-fully-active owners would not be "actively needed" or "protected"; it would be thus suspendable for the duration of its https://html.spec.whatwg.org/#between-loads-shared-worker-timeout, or for as long as it has clients, respectively. This is useful for keeping the worker around for a bit so that it doesn't need to be re-initialized from scratch later, but it doesn't guarantee that the worker can perform any last-minute work in this period. Extended lifetime shared workers allow the worker to stay "actively needed" and thus not "suspendable" during the extended lifetime timeout. This ensures they keep running until the timeout expires.

---------

Co-authored-by: Dominic Farolino <domfarolino@gmail.com>

Author: domenic

source

@@ -4452,6 +4452,7 @@ a.setAttribute('href', 'https://example.com/'); // change the content attribute
      <li><dfn data-x="on-fetch-request-algorithm" data-x-href="https://w3c.github.io/ServiceWorker/#on-fetch-request-algorithm">handle fetch</dfn></li>
      <li><dfn data-x="scope-match-algorithm" data-x-href="https://w3c.github.io/ServiceWorker/#scope-match-algorithm">match service worker registration</dfn></li>
      <li><dfn data-x="dfn-service-worker" data-x-href="https://w3c.github.io/ServiceWorker/#dfn-service-worker">service worker</dfn></li>
+     <li><dfn data-x-href="https://w3c.github.io/ServiceWorker/#dfn-service-worker-client">service worker client</dfn></li>
      <li><dfn data-x="serviceworkercontainer-service-worker-client" data-x-href="https://w3c.github.io/ServiceWorker/#serviceworkercontainer-service-worker-client">service worker client</dfn></li>
      <li><dfn data-x-href="https://w3c.github.io/service-workers/#dfn-service-worker-registration">service worker registration</dfn></li>
      <li><dfn data-x-href="https://w3c.github.io/ServiceWorker/#serviceworker"><code>ServiceWorker</code></dfn> interface</li>
@@ -130786,9 +130787,10 @@ interface <dfn interface>SharedWorkerGlobalScope</dfn> : <span>WorkerGlobalScope
   <span>origin</span>), <dfn data-x="concept-SharedWorkerGlobalScope-constructor-url">constructor
   URL</dfn> (a <span>URL record</span>), and <dfn
   data-x="concept-SharedWorkerGlobalScope-credentials">credentials</dfn> (a <span
-  data-x="concept-request-credentials-mode">credentials mode</span>). They are initialized when the
-  <code>SharedWorkerGlobalScope</code> object is created, in the <span>run a worker</span>
-  algorithm.</p>
+  data-x="concept-request-credentials-mode">credentials mode</span>), and <dfn
+  data-x="concept-SharedWorkerGlobalScope-extended-lifetime">extended lifetime</dfn> (a boolean).
+  They are initialized when the <code>SharedWorkerGlobalScope</code> object is created, in the
+  <span>run a worker</span> algorithm.</p>
 
   </div>
 
@@ -130907,13 +130909,77 @@ interface <dfn interface>SharedWorkerGlobalScope</dfn> : <span>WorkerGlobalScope
   <p class="note">A typical value for the <span>between-loads shared worker timeout</span> might be
   5 seconds.</p>
 
+  <p>A user agent has an <span>implementation-defined</span> value, the <dfn>extended lifetime
+  shared worker timeout</dfn>, which is some amount of time. This represents how long the user agent
+  allows shared workers which the web developer has requested be given an extended lifetime, to
+  survive and perform work after all of their <span data-x="owner set">owners</span> have
+  disappeared. User agents should choose a value that is equal to the longest lifetime that a
+  service worker can stay alive without any <span data-x="service worker client">clients</span>, and
+  must not choose a value that is longer than that amount of time.</p>
+
+  <p class="note">A typical value for the <span>extended lifetime shared worker timeout</span> could
+  be anywhere from 10 seconds to 5 minutes, depending on the implementation's individual policies
+  regarding background work being performed by an origin without a user-visible representation.</p>
+
   <hr>
 
+  <div algorithm>
+  <p>A <code>WorkerGlobalScope</code> <var>global</var> is <dfn data-x="in extended lifetime
+  worker">in extended lifetime</dfn> if the following algorithm returns true:</p>
+
+  <ol>
+   <li><p>If <var>global</var> is not a <code>SharedWorkerGlobalScope</code>, then return
+   false.</p></li>
+
+   <li><p>If <var>global</var>'s <span
+   data-x="concept-SharedWorkerGlobalScope-extended-lifetime">extended lifetime</span> is false,
+   then return false.</p></li>
+
+   <li><p>If <var>global</var>'s <span>owner set</span> <span data-x="list is empty">is
+   empty</span>, but has been empty for less than the user agent's <span>extended lifetime shared
+   worker timeout</span>, then return true.</p></li>
+
+   <li>
+    <p><span data-x="list iterate">For each</span> <var>owner</var> of <var>global</var>'s
+    <span>owner set</span>:</p>
+
+    <ol>
+     <li>
+      <p>If <var>owner</var> is a <code>Document</code> that is <span>fully active</span>, then
+      return false:</p>
+
+      <p class="note">In this case <var>global</var> will be <span data-x="active needed
+      worker">actively needed</span>, but it's not in extended lifetime.</p>
+     </li>
+    </ol>
+   </li>
+
+   <li>
+    <p><span data-x="list iterate">For each</span> <var>owner</var> of <var>global</var>'s
+    <span>owner set</span>:</p>
+
+    <ol>
+     <li><p>If <var>owner</var> is a <code>Document</code> and the amount of time that
+     <var>owner</var> that has been non-<span>fully active</span> is less than the user agent's
+     <span>extended lifetime shared worker timeout</span>, then return true.</p></li>
+
+     <li><p>If <var>owner</var> is a <code>WorkerGlobalScope</code> that is <span data-x="in
+     extended lifetime worker">in extended lifetime</span>, then return true.</p></li>
+    </ol>
+   </li>
+
+   <li><p>Return false.</p></li>
+  </ol>
+  </div>
+
   <div algorithm>
   <p>A <code>WorkerGlobalScope</code> <var>global</var> is <dfn data-x="active needed
   worker">actively needed</dfn> if the following algorithm returns true:</p>
 
   <ol>
+   <li><p>If <var>global</var> is <span data-x="in extended lifetime worker">in extended
+   lifetime</span>, then return true.</p></li>
+
    <li>
     <p><span data-x="list iterate">For each</span> <var>owner</var> of <var>global</var>'s
     <span>owner set</span>:</p>
@@ -130939,6 +131005,9 @@ interface <dfn interface>SharedWorkerGlobalScope</dfn> : <span>WorkerGlobalScope
    <li><p>If <var>global</var> is not <span data-x="active needed worker">actively needed</span>,
    then return false.</p></li>
 
+   <li><p>If <var>global</var> is <span data-x="in extended lifetime worker">in extended
+   lifetime</span>, then return true.</p></li>
+
    <li><p>If <var>global</var> is a <code>SharedWorkerGlobalScope</code>, then return true.</p></li>
 
    <li><p>If <var>global</var>'s <span>the worker's ports</span> is not <span data-x="list is
@@ -130960,6 +131029,9 @@ interface <dfn interface>SharedWorkerGlobalScope</dfn> : <span>WorkerGlobalScope
    <li><p>If <var>global</var>'s <span>owner set</span> is not <span data-x="list is
    empty">empty</span>, then return true.</p></li>
 
+   <li><p>If <var>global</var> is <span data-x="in extended lifetime worker">in extended
+   lifetime</span>, then return true.</p></li>
+
    <li>
     <p>If all of the following are true:</p>
 
@@ -130985,6 +131057,11 @@ interface <dfn interface>SharedWorkerGlobalScope</dfn> : <span>WorkerGlobalScope
    <p>The following relationships hold between these terms:</p>
 
    <ul>
+    <li><p>Every <code>WorkerGlobalScope</code> that is <span data-x="in extended lifetime
+    worker">in extended lifetime</span> is <span data-x="active needed worker">actively
+    needed</span>, <span data-x="protected worker">protected</span>, and <span data-x="permissible
+    worker">permissible</span>.</p></li>
+
     <li><p>Every <code>WorkerGlobalScope</code> that is <span data-x="active needed worker">actively
     needed</span> or <span data-x="protected worker">protected</span> is <span data-x="permissible
     worker">permissible</span>.</p></li>
@@ -131015,11 +131092,17 @@ interface <dfn interface>SharedWorkerGlobalScope</dfn> : <span>WorkerGlobalScope
    </ul>
   </div>
 
-  <p class="note" id="note-between-loads-shared-worker-timeout-lifetime">The <span>between-loads
-  shared worker timeout</span> only influences the definition of <span data-x="permissible
-  worker">permissible</span>, not <span data-x="protected worker">protected</span>, and so
-  implementations are not required to keep shared workers alive for that duration. Rather, they are
-  required to close shared workers after the timeout is reached.</p>
+  <div class="note" id="note-between-loads-shared-worker-timeout-lifetime">
+   <p>The <span>between-loads shared worker timeout</span> only influences the definition of <span
+   data-x="permissible worker">permissible</span>, not <span data-x="protected
+   worker">protected</span>, and so implementations are not required to keep shared workers alive
+   for that duration. Rather, they are required to close shared workers after the timeout is
+   reached.</p>
+
+   <p>In contrast, the <span>extended lifetime shared worker timeout</span> does influence the
+   definition of <span data-x="protected worker">protected</span>, so implementations are required
+   to keep shared workers alive (and not suspended) for that duration.</p>
+  </div>
 
   <div algorithm>
   <p>A <code>WorkerGlobalScope</code> <var>global</var> is <dfn data-x="suspendable
@@ -131128,6 +131211,11 @@ interface <dfn interface>SharedWorkerGlobalScope</dfn> : <span>WorkerGlobalScope
      <li><p>Set <var>worker global scope</var>'s <span
      data-x="concept-SharedWorkerGlobalScope-credentials">credentials</span> to
      <var>options</var>["<code data-x="dom-WorkerOptions-credentials">credentials</code>"].</p></li>
+
+     <li><p>Set <var>worker global scope</var>'s <span
+     data-x="concept-SharedWorkerGlobalScope-extended-lifetime">extended lifetime</span> to
+     <var>options</var>["<code
+     data-x="dom-SharedWorkerOptions-extendedLifetime">extendedLifetime</code>"].</p></li>
     </ol>
    </li>
 
@@ -131693,11 +131781,15 @@ enum <dfn enum>WorkerType</dfn> { "classic", "module" };
 
   <pre><code class="idl">[Exposed=Window]
 interface <dfn interface>SharedWorker</dfn> : <span>EventTarget</span> {
-  <span data-x="dom-SharedWorker">constructor</span>((<code data-x="tt-trustedscripturl">TrustedScriptURL</code> or USVString) scriptURL, optional (DOMString or <span>WorkerOptions</span>) options = {});
+  <span data-x="dom-SharedWorker">constructor</span>((<code data-x="tt-trustedscripturl">TrustedScriptURL</code> or USVString) scriptURL, optional (DOMString or <span>SharedWorkerOptions</span>) options = {});
 
   readonly attribute <span>MessagePort</span> <span data-x="dom-SharedWorker-port">port</span>;
 };
-<span>SharedWorker</span> includes <span>AbstractWorker</span>;</code></pre>
+<span>SharedWorker</span> includes <span>AbstractWorker</span>;
+
+dictionary <dfn dictionary>SharedWorkerOptions</dfn> : <span>WorkerOptions</span> {
+  boolean <dfn dict-member for="SharedWorkerOptions" data-x="dom-SharedWorkerOptions-extendedLifetime">extendedLifetime</dfn> = false;
+};</code></pre>
 
   <dl class="domintro">
    <dt><code data-x=""><var>sharedWorker</var> = new <span subdfn data-x="dom-SharedWorker">SharedWorker</span>(<var>scriptURL</var> [, <var>name</var> ])</code></dt>
@@ -131725,11 +131817,17 @@ interface <dfn interface>SharedWorker</dfn> : <span>EventTarget</span> {
      <li><p><code data-x="dom-WorkerOptions-credentials">credentials</code> can be used to specify
      how <var>scriptURL</var> is fetched, but only if <code
      data-x="dom-WorkerOptions-type">type</code> is set to "<code data-x="">module</code>".</p></li>
+
+     <li><p><code data-x="dom-SharedWorkerOptions-extendedLifetime">extendedLifetime</code> can be
+     set to request that the newly-created global environment be given extra time to perform its
+     operations even after all of its <span data-x="owner set">owners</span> have disappeared. This
+     can be useful, for example, for performing asynchronous work after page unload.</p></li>
     </ul>
 
-    <p>Note that attempting to construct a shared worker with <var>options</var> whose <code
-    data-x="dom-WorkerOptions-type">type</code>, or <code
-    data-x="dom-WorkerOptions-credentials">credentials</code> values mismatch those
+    <p class="warning">Note that attempting to construct a shared worker with <var>options</var>
+    whose <code data-x="dom-WorkerOptions-type">type</code>, <code
+    data-x="dom-WorkerOptions-credentials">credentials</code>, or <code
+    data-x="dom-SharedWorkerOptions-extendedLifetime">extendedLifetime</code> values mismatch those
     of an existing shared worker with the same <span
     data-x="concept-SharedWorkerGlobalScope-constructor-url">constructor URL</span> and <span
     data-x="concept-WorkerGlobalScope-name">name</span>, will cause the returned
@@ -131880,12 +131978,17 @@ interface <dfn interface>SharedWorker</dfn> : <span>EventTarget</span> {
       <ul>
        <li><p><var>workerGlobalScope</var>'s <span
        data-x="concept-WorkerGlobalScope-type">type</span> is not equal to <var>options</var>["<code
-       data-x="dom-WorkerOptions-type">type</code>"]; or</p></li>
+       data-x="dom-WorkerOptions-type">type</code>"];</p></li>
 
        <li><p><var>workerGlobalScope</var>'s <span
        data-x="concept-SharedWorkerGlobalScope-credentials">credentials</span> is not equal to
-       <var>options</var>["<code
-       data-x="dom-WorkerOptions-credentials">credentials</code>"]</p></li>
+       <var>options</var>["<code data-x="dom-WorkerOptions-credentials">credentials</code>"];
+       or</p></li>
+
+       <li><p><var>workerGlobalScope</var>'s <span
+       data-x="concept-SharedWorkerGlobalScope-extended-lifetime">extended lifetime</span> is not
+       equal to <var>options</var>["<code
+       data-x="dom-SharedWorkerOptions-extendedLifetime">extendedLifetime</code>"],</p></li>
       </ul>
 
       <p>then:</p>