Unloading of workers (and hence Platform Collector)

[kenchris]

Find the right hooks to make sure we inform the platform collector when workers are unloaded

[kenchris]

Potentially relevant:

https://html.spec.whatwg.org/#suspendable-worker
https://html.spec.whatwg.org/#dom-workerglobalscope-closing

Closing orphan workers: Start monitoring the worker such that no sooner than it stops being a protected worker, and no later than it stops being a permissible worker, worker global scope's closing flag is set to true.

Suspending workers: Start monitoring the worker, such that whenever worker global scope's closing flag is false and the worker is a suspendable worker, the user agent suspends execution of script in that worker until such time as either the closing flag switches to true or the worker stops being a suspendable worker.

Once the WorkerGlobalScope's closing flag is set to true, the event loop's task queues must discard any further tasks that would be added to them (tasks already on the queue are unaffected except where otherwise specified). Effectively, once the closing flag is true, timers stop firing, notifications for all pending background operations are dropped, etc.

[kenchris]

This reminds me that the closing and unloading of the worker should be handled by garbage collection as we do in Generic Sensors:

When a Sensor object whose [[state]] is "activated" or "activating" is garbage collected, the user agent must invoke deactivate a sensor object with this object as argument.

[kenchris]

We probably want to handle suspension (bfcache, suspendable worker, non-fully active document).

@rakuco does Generic Sensors handle that? It seems to only send events to active documents (why not fully active?) so I assume that you still keep the platform sensors active while in bfcache etc

[kenchris]

Web Bluetooth has a note about disconnecting on garbage collection:

Note: Disconnecting on garbage collection ensures that the UA doesn’t keep consuming resources on the remote device unnecessarily.

[rakuco]

Sorry for the delay here.

@rakuco does Generic Sensors handle that? It seems to only send events to active documents (why not fully active?) so I assume that you still keep the platform sensors active while in bfcache etc

Support for the "fully active" concept is pending (see w3c/sensors#415). I believe bfcache is not a concern because sensors are stopped when the page is not visible, which is the case when a page is entering the bfcache if I recall correctly (that's the case for Screen Wake Lock in the Chromium implementation at least).

Although the spec says sensors are exposed to workers, the Blink implementation currently only exposes them to Window.

Does this help you?