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Define agents and agent clusters #2521

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Define agents and agent clusters #2521

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736c6e7
Define agents and agent clusters
annevk Apr 11, 2017
7187cdc
adopt all of Maciej's suggestions
annevk Apr 25, 2017
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Expand Up @@ -2855,6 +2855,8 @@ a.setAttribute('href', 'https://example.com/'); // change the content attribute

<ul class="brief">
<li><dfn data-x-href="https://tc39.github.io/ecma262/#active-function-object">active function object</dfn></li>
<li><dfn data-x-href="https://tc39.github.io/ecma262/#sec-agents">agent</dfn> and
<dfn data-x-href="https://tc39.github.io/ecma262/#sec-agent-clusters">agent cluster</dfn></li>
<li><dfn data-x-href="https://tc39.github.io/ecma262/#sec-automatic-semicolon-insertion">automatic semicolon insertion</dfn></li>
<li>The <dfn data-x-href="https://tc39.github.io/ecma262/#current-realm">current Realm Record</dfn></li>
<li><dfn data-x-href="https://tc39.github.io/ecma262/#early-error-rule">early error</dfn></li>
Expand Down Expand Up @@ -2936,6 +2938,7 @@ a.setAttribute('href', 'https://example.com/'); // change the content attribute
<li>The <dfn data-x="js-abstract-equality" data-x-href="https://tc39.github.io/ecma262/#sec-abstract-equality-comparison">Abstract Equality Comparison</dfn> algorithm</li>
<li>The <dfn data-x="js-strict-equality" data-x-href="https://tc39.github.io/ecma262/#sec-strict-equality-comparison">Strict Equality Comparison</dfn> algorithm</li>
<li>The <dfn data-x-href="https://tc39.github.io/ecma262/#sec-date-objects"><code>Date</code></dfn> class</li>
<li>The <dfn data-x-href="https://tc39.github.io/ecma262/#sec-sharedarraybuffer-objects"><code>SharedArrayBuffer</code></dfn> class</li>
<li>The <dfn data-x-href="https://tc39.github.io/ecma262/#sec-native-error-types-used-in-this-standard-typeerror"><code>TypeError</code></dfn> class</li>
<li>The <dfn data-x="js-RangeError" data-x-href="https://tc39.github.io/ecma262/#sec-native-error-types-used-in-this-standard-rangeerror"><code>RangeError</code></dfn> class</li>
<li>The <dfn data-x="js-typeof" data-x-href="https://tc39.github.io/ecma262/#sec-typeof-operator"><code>typeof</code></dfn> operator</li>
Expand Down Expand Up @@ -3780,6 +3783,7 @@ a.setAttribute('href', 'https://example.com/'); // change the content attribute
<li><dfn data-x-href="https://w3c.github.io/ServiceWorker/#dfn-serviceworker-link">serviceworker link</dfn></li>
<li><dfn data-x-href="https://w3c.github.io/ServiceWorker/#serviceworker"><code>ServiceWorker</code></dfn> interface</li>
<li><dfn data-x-href="https://w3c.github.io/ServiceWorker/#serviceworkercontainer"><code>ServiceWorkerContainer</code></dfn> interface</li>
<li><dfn data-x-href="https://w3c.github.io/ServiceWorker/#serviceworkerglobalscope"><code>ServiceWorkerGlobalScope</code></dfn> interface</li>
<li><dfn data-x-href="https://w3c.github.io/ServiceWorker/#dfn-use-cache">use cache</dfn></li>
</ul>

Expand Down Expand Up @@ -3905,6 +3909,17 @@ a.setAttribute('href', 'https://example.com/'); // change the content attribute
</ul>
</dd>

<dt>Worklets</dt>

<dd>
<p>The following feature is defined in the <cite>Worklets</cite> specification: <ref
spec=WORKLETS></p>

<ul class="brief">
<li><dfn data-x-href="https://drafts.css-houdini.org/worklets/#workletglobalscope"><code>WorkletGlobalScope</code></dfn></li>
</ul>
</dd>

</dl>

<hr>
Expand Down Expand Up @@ -88451,6 +88466,133 @@ import "https://example.com/foo/../module2.js";</pre>
data-x="concept-module-script-module-record">module record</span>.</p></li>
</ol>

<h5>Integration with the JavaScript agent formalism</h5>

<p>JavaScript defines the concept of an <span>agent</span>. Until such a time that this standard
has a better handle on lifetimes, we define five types of <span data-x="agent">agents</span> that
user agents must allocate at the appropriate time.</p>

<p class="note">In the future, when this specification has a better handle on lifetimes, we hope
to define exactly when <span data-x="agent">agents</span> and <span data-x="agent cluster">agent
clusters</span> are created.</p>

<p class="&#x0058;&#x0058;&#x0058;">JavaScript is expected to define <span
data-x="agent">agents</span> in more detail; in particular that they hold a set of <span
data-x="concept-global-object-realm">realms</span>: <a
href="https://github.com/tc39/ecma262/issues/882">tc39/ecma262 issue #882</a>.</p>

<dl>
<dt><dfn data-export="">Similar-origin window agent</dfn></dt>
<dd>
<p>An <span>agent</span> whose [[CanBlock]] is false and whose set of <span
data-x="JavaScript realm">realms</span> consists of all <span
data-x="concept-global-object-realm">realms</span> of <code>Window</code> objects whose
<span>relevant settings object</span>'s <span>responsible browsing context</span> is in the same
<span>unit of related similar-origin browsing contexts</span>.</p>

<p class="note">Two <code>Window</code> objects that are <span>same origin</span> can be in
different <span data-x="similar-origin window agent">similar-origin window agents</span>, for
instance if they are each in their own <span>unit of related similar-origin browsing
contexts</span>.</p>
</dd>

<dt><dfn data-export="">Dedicated worker agent</dfn></dt>
<dd><p>An <span>agent</span> whose [[CanBlock]] is true and whose set of <span data-x="JavaScript
realm">realms</span> consists of a single <code>DedicatedWorkerGlobalScope</code> object's <span
data-x="concept-global-object-realm">Realm</span>.</p></dd>

<dt><dfn data-export="">Shared worker agent</dfn></dt>
<dd><p>An <span>agent</span> whose [[CanBlock]] is true and whose set of <span data-x="JavaScript
realm">realms</span> consists a single <code>SharedWorkerGlobalScope</code> object's <span
data-x="concept-global-object-realm">Realm</span>.</p></dd>

<dt><dfn data-export="">Service worker agent</dfn></dt>
<dd><p>An <span>agent</span> whose [[CanBlock]] is false and whose set of <span data-x="JavaScript
realm">realms</span> consists of a single <code>ServiceWorkerGlobalScope</code> object's <span
data-x="concept-global-object-realm">Realm</span>.</p></dd>

<dt><dfn data-export="">Worklet agent</dfn></dt>
<dd>
<p>An <span>agent</span> whose [[CanBlock]] is false and whose set of <span
data-x="JavaScript realm">realms</span> consists of a single <code>WorkletGlobalScope</code>
object's <span data-x="concept-global-object-realm">Realm</span>.</p>

<p class="note">While conceptually it might be cleaner for worklets that end up with multiple
realms to put all those in the same agent, it is not observable in practice.</p>
</dd>
</dl>

<h5>Integration with the JavaScript agent cluster formalism</h5>

<p><dfn>Can share memory with</dfn> defines an equivalence relation. An <span>agent cluster</span>
consists of all <span data-x="agent">agents</span> in the same equivalence class with respect to
the <span>can share memory with</span> equivalence relation.</p>

<p>A <span>similar-origin window agent</span>, <span>dedicated worker agent</span>, <span>shared
worker agent</span>, or <span>service worker agent</span>, <var>agent</var>, <span>can share
memory with</span> any <span>dedicated worker agent</span> whose single <span data-x="JavaScript
realm">realm</span>'s <span data-x="concept-realm-global">global object</span>'s <span>owner
set</span> contains an item whose <span data-x="concept-relevant-realm">relevant Realm</span>
belongs to <var>agent</var>.</p>

<p class="note">We use item above as an <span>owner set</span> can contain <code>Document</code>
objects.</p>

<p class="&#x0058;&#x0058;&#x0058;">A <span>worklet agent</span> &hellip; currently worklets have
no clearly defined owner, see: <a
href="https://github.com/w3c/css-houdini-drafts/issues/224">w3c/css-houdini-drafts issue
#224</a>.</p>

<p>In addition, any <span>agent</span> <var>A</var> <span>can share memory with</span>:</p>

<ul class="brief">
<li><var>A</var>,</li>

<li>any <span>agent</span> <var>B</var> such that <var>B</var> <span>can share memory with</span>
<var>A</var>, and</li>

<li>any <span>agent</span> <var>B</var> such that there exists an <span>agent</span>
<var>C</var>, where <var>A</var> <span>can share memory with</span> <var>C</var> and <var>C</var>
<span>can share memory with</span> <var>B</var>.</li>
</ul>

<p>The <span>agent cluster</span> concept is crucial for defining the JavaScript memory model, and
in particular among which <span data-x="agent">agents</span> the backing data of
<code>SharedArrayBuffer</code> objects can be shared.</p>

<div class="example">
<p>The following pairs of global objects are each within the same <span>agent cluster</span>, and
thus can use <code>SharedArrayBuffer</code> instances to share memory with each other:</p>

<ul class="brief">
<li>A <code>Window</code> object and a dedicated worker that it created.</li>

<li>A worker (of any type) and a dedicated worker it created.</li>

<li>A <code>Window</code> object <var>A</var> and the <code>Window</code> object of an
<code>iframe</code> element that <var>A</var> created that could be <span>same
origin-domain</span> with <var>A</var>.</li>

<li>A <code>Window</code> object and a <span>same origin-domain</span> <code>Window</code>
object that opened it.</li>
</ul>

<p>The following pairs of global objects are <em>not</em> within the same <span>agent
cluster</span>, and thus cannot share memory:</p>

<ul class="brief">
<li>A <code>Window</code> object and a shared worker it created.</li>

<li>A worker (of any type) and a shared worker it created.</li>

<li>A <code>Window</code> object and a service worker it created.</li>

<li>A <code>Window</code> object <var></var> and the <code>Window</code> object of an
<code>iframe</code> element that <var>A</var> created that cannot be <span>same
origin-domain</span> with <var>A</var>.</li>
</ul>
</div>

</div>


Expand Down Expand Up @@ -119795,6 +119937,9 @@ INSERT INTERFACES HERE
<dt id="refsWHATWGWIKI">[WHATWGWIKI]</dt>
<dd><cite><a href="https://wiki.whatwg.org/">The WHATWG Wiki</a></cite>. WHATWG.</dd>

<dt id="refsWORKLETS">[WORKLETS]</dt>
<dd><cite><a href="https://drafts.css-houdini.org/worklets/">Worklets</a></cite>. I. Kilpatrick. W3C.</dd>

<dt id="refsWSP">[WSP]</dt>
<dd><cite><a href="https://tools.ietf.org/html/rfc6455">The WebSocket protocol</a></cite>, I. Fette, A. Melnikov. IETF.</dd>

Expand Down