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Async scheduling of batched updates #34295

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Async scheduling of batched updates #34295

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60c80d1
Await the next animation frame between core data API calls in __exper…
adamziel Aug 25, 2021
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adamziel Aug 25, 2021
5fb1765
Fix unit tests
adamziel Aug 25, 2021
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adamziel Aug 25, 2021
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Add a comment stating that this, ideally, is only a temporary solutio…
adamziel Aug 25, 2021
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19 changes: 18 additions & 1 deletion packages/core-data/src/actions.js
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Original file line number Diff line number Diff line change
Expand Up @@ -643,7 +643,24 @@ export function* __experimentalBatch( requests ) {
);
},
};
const resultPromises = requests.map( ( request ) => request( api ) );
const resultPromises = [];
const awaitNextFrame = () =>
__unstableAwaitPromise(
new Promise( ( resolve ) =>
window.requestAnimationFrame( () => resolve() )
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requestAnimationFrame is not the best function to call here. It always waits 16ms for the next frame, even if the browser is not busy with anything else. Dispatching 60 parallel requests will be spread over exactly one second. setTimeout or setImmediate would be better.

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Also this could only happen after the first saveEntityRecord which would already trigger the progress indicator.

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setTimeout might not be better either, some browsers will only fire the callback after a certain amount of time (mostly 1 second) if the tab is in the background. setImmediate is non-standard, so probably not the best either. I wonder if using Promise.resolve() to schedule a microtask work here?

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Promise.resolve() wouldn't prevent freezing of the UI. It schedules a microtask right after the current script finishes running, and no other event, like user input or an animation frame, can squeeze in between them.

setImmediate, appropriately polyfilled, is probably the best. Just be careful to not choose a polyfill that uses queueMicrotask or something equivalent. The popular async package has a polyfill that does exactly that, so the danger is real.

)
);
for ( const request of requests ) {
resultPromises.push( request( api ) );

// Each request( api ) is pretty fast, but when there's a lot of them it may block the browser for a few
// seconds. Let's split this long, blocking task into bite-sized pieces scheduled separately to give the
// browser a space for processing other tasks.
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can you clarify more what request calls are doing here? Can you share examples? I have trouble understanding why this would be blocking the UI.

//
// Ideally this will be just a temporary fix and the blocking would not be an issue in the first place.
// Replacing redux-rungen usage with async thunks may help with that, see https://github.com/WordPress/gutenberg/pull/27276
yield awaitNextFrame();
}
const [ , ...results ] = yield __unstableAwaitPromise(
Promise.all( [ batch.run(), ...resultPromises ] )
);
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7 changes: 6 additions & 1 deletion packages/core-data/src/test/actions.js
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Expand Up @@ -340,8 +340,13 @@ describe( '__experimentalBatch', () => {
),
};
const dispatch = () => actions;
// Run generator up to the last `yield awaitNextFrame( )`.
generator.next( dispatch );
generator.next();
generator.next();
const { value: awaitPromiseControl } = generator.next();

// Run generator up to `yield __unstableAwaitPromise( ... )`.
const { value: awaitPromiseControl } = generator.next( dispatch );
expect( actions.saveEntityRecord ).toHaveBeenCalledWith(
'root',
'widget',
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