Hook the renderer into the scheduler through a classic-default adapter by NullVoxPopuli-ai-agent · Pull Request #21553 · emberjs/ember.js

NullVoxPopuli-ai-agent · 2026-08-07T22:15:44Z

Targets #21552's branch: the interface gains its first consumer, wired so that today's behavior is the default and the perf benefits arrive by swapping the strategy later.

What this adds

An internal renderer seam on Strategy: optional _scheduleRevalidate(flush) (underscore, @internal). The renderer always schedules revalidation through the active strategy via this callback-based hook — deliberately not the public promise API, since revalidation is hotter than any user phase and promise-per-invalidation overhead was measured as a real cost class during the SPIKE: every rendering-performance lever combined (RFC 957 end state + VM optimizations) #21520 spike.
ClassicStrategy as the ambient default (private module, no registration required): revalidation is byte-for-byte today's scheduleOnce('render', …) with the same dedupe semantics (stable flush callback per renderer), and the public phase functions become meaningful under classic timing — render() → the render queue, layout() → afterRender, composite() re-scheduled behind layout's entries within the same flush, next() → runloop next, idle() → requestIdleCallback with a starvation timeout (fully-idle pages never grant bare rIC — the Implement RFC #957: Render Aware Scheduler Interface #21493 lesson).
getStrategy falls back to classic instead of asserting; registerStrategy keeps its double-registration assert and remains the swap seam. A registered strategy without the internal seam leaves the renderer on classic scheduling.

Verification

Full suite: 9440 tests, 0 failures — with the renderer routed through the seam and classic as default, which is the no-timing-change proof.
Full repo lint (eslint + prettier + docs) exits 0.
Scheduler package tests updated: the assert-when-none test becomes the ambient-classic-fallback test (phases resolve in render → layout → composite order under runloop semantics), plus a seam-delegation test.

The path this sets up

When a render-aware strategy (the #21520 spike's clock: microtask-window chain classification, unclamped-macrotask/rAF race, one-render-per-tick) implements _scheduleRevalidate and becomes the default, the renderer picks up coalesced, frame-aligned revalidation with no further renderer changes — that swap is where the spike's measured wins (6–24x async, 2.5x dbmon) transfer.

🤖 Generated with Claude Code

The scheduler interface gains its first consumer. The renderer now always schedules revalidation through the active strategy via an internal, callback-based seam (_scheduleRevalidate) -- revalidation is hotter than any user phase, so the renderer does not allocate promises per invalidation. The ambient default is a new ClassicStrategy that reproduces today's behavior exactly: revalidation is the same scheduleOnce('render', ...) with the same dedupe (the flush callback is stable per renderer), and the public phase functions map onto the runloop's queues (render -> 'render', layout -> 'afterRender', composite behind layout within the same flush, next -> runloop next, idle -> requestIdleCallback with a starvation timeout). No registration required; existing applications observe no timing change -- the full suite passes unmodified. registerStrategy remains the swap seam: a render-aware strategy that implements _scheduleRevalidate takes over revalidation scheduling, which is where the performance benefits arrive when such a strategy becomes the default. A registered strategy without the seam leaves the renderer on classic scheduling. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

NullVoxPopuli · 2026-08-07T22:30:02Z

-    _backburner.scheduleOnce('render', this, this.revalidate, renderer);
+    this.#renderer = renderer;
+
+    const strategy = _getStrategy();


this should happen during construction time, i believe, because we don't want to re-check all this strategy stuff eveyr revalidation.

Additionally, I think you'll want to hook in to the environment, since that's where existing backburner integration is (and the scheduler is replacing backburner eventually

NullVoxPopuli · 2026-08-07T22:33:23Z

+ *
+ * @internal
+ */
+export function _getStrategy(): Strategy {


this function is redundant and unneeded. don't be silly

Gone — _getStrategy deleted in df40e9e.

NullVoxPopuli · 2026-08-07T22:33:58Z

 */
 export function render(): Promise<void> {
-  return getStrategy('render').render();
+  return getStrategy().render();


why call getStrategy so much when we can just directly access registeredStrategy?

Agreed and removed: getStrategy is gone entirely. The phase functions and the renderer access the exported live binding _registeredStrategy directly (with a pre-boot assert in the phase functions).

NullVoxPopuli · 2026-08-07T22:35:06Z

+  // the classic strategy is the ambient default: existing applications
+  // keep today's runloop scheduling with no registration required, and
+  // `registerStrategy` swaps in a render-aware implementation
+  return registeredStrategy ?? classicStrategy;


classicStrategy probably shouldn't be returned here (I'm questiening the entire purpose of getStrategy atm)

maybe we setStrategy in the environment (glimmer<->ember hookup) and pass the classicStrategy there

Took exactly this direction in df40e9e: no ambient fallback anywhere — the glimmer<->ember hookup (environment.ts, next to setGlobalContext) does registerStrategy(classicStrategy) at initialization, so a booted app always has the classic strategy unless it swaps one in. registerStrategy permits one swap over the classic default and still asserts on conflicting registrations. Full suite 9425/0 and repo lint green with the rework.

Review feedback: no getStrategy indirection and no ambient fallback. The active strategy is an exported live binding the phase functions and the renderer access directly (with a pre-boot assert), and the classic default is established where the glimmer<->ember hookup happens -- registerStrategy(classicStrategy) at environment initialization. registerStrategy permits one application swap over the classic default and still asserts on conflicting registrations. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

NullVoxPopuli · 2026-08-07T22:49:00Z

+   *
+   * @internal
+   */
+  _scheduleRevalidate?(flush: () => void): void;


why is this here? we can't add to the interface of the scheduler, even for compat

NullVoxPopuli · 2026-08-07T22:49:21Z

@@ -1,4 +1,5 @@
 import { assert } from '@ember/debug';
+import classicStrategy from '@ember/scheduler/-private/classic';


we should not import this here.

NullVoxPopuli · 2026-08-07T22:49:55Z

-    registeredStrategy === null || registeredStrategy === strategy
+    _registeredStrategy === null ||
+      _registeredStrategy === strategy ||
+      _registeredStrategy === classicStrategy


this third comparison is unneeded, and would be handled by the comparison above

to test this proper, you'd want a well known symbol to check on the internal strategies, because we do want those to be overwritten

NullVoxPopuli · 2026-08-07T22:58:42Z

    }
  }

+  #renderer: BaseRenderer | null = null;


I do not believe we are done.

Because we haven't wired up all our internals to the scheduler, a user swapping out the scheduler would see no benefit.

#21520 made a lot of progress on that work, and you'll need to copy some of that here (though, only insofar as it applies to enabling the classic strategy.

This is also way too much code.

Read https://github.com/runspired/rfcs/blob/modernized-scheduler/text/0957-modernized-scheduler.md again

NullVoxPopuli · 2026-08-07T23:02:31Z

temporray misunderstanding

NullVoxPopuli reviewed Aug 7, 2026

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NullVoxPopuli mentioned this pull request Aug 7, 2026

Implement RFC #957: Render Aware Scheduler Interface #21552

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NullVoxPopuli marked this pull request as draft August 7, 2026 22:39

NullVoxPopuli reviewed Aug 7, 2026

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NullVoxPopuli closed this Aug 7, 2026

NullVoxPopuli deleted the scheduler-adapter branch August 7, 2026 23:02

		@@ -1,4 +1,5 @@
		import { assert } from '@ember/debug';
		import classicStrategy from '@ember/scheduler/-private/classic';

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NullVoxPopuli-ai-agent commented Aug 7, 2026

What this adds

Verification

The path this sets up

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NullVoxPopuli commented Aug 7, 2026

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