fix(producer): chunk capture round-robins only for callers that bill wall time (#6405)

* fix(producer): chunk capture round-robins only for callers that bill wall time

* fix(engine): worker, extraction and encoder sizing read the CPU quota, not the host core count

* Revert "fix(engine): worker, extraction and encoder sizing read the CPU quota, not the host core count"

This reverts commit cdd4d858c8.

* chore(producer): drop the doc comments the comment ratchet rejects

packages/aws-lambda/src/handler.test.ts

@@ -767,8 +767,11 @@ describe("handler dispatch", () => {
     }
     const options = renderChunkMock.mock.calls.map((call) => (call as unknown[])[3]);
     expect(options).toEqual([
-      { maxCaptureWorkers: undefined },
-      { maxCaptureWorkers: Math.max(1, Math.min(5, availableParallelism() - 1)) },
+      { maxCaptureWorkers: undefined, interleaveCapture: true },
+      {
+        maxCaptureWorkers: Math.max(1, Math.min(5, availableParallelism() - 1)),
+        interleaveCapture: true,
+      },
     ]);
     const captures = logged
       .filter((line) => line.includes('"chunk_capture"'))

packages/aws-lambda/src/handler.ts

@@ -647,6 +647,7 @@ async function handleRenderChunk(
 
     const result: ChunkResult = await primitive(planDir, event.ChunkIndex, chunkOutputBase, {
       maxCaptureWorkers: lambdaMaxCaptureWorkers(),
+      interleaveCapture: true,
     });
     logEvent({
       event: "chunk_capture",
@@ -703,6 +704,7 @@ async function handleRenderChunkV2(
     );
     const result = await primitive(planDir, event.ChunkIndex, chunkOutputBase, {
       maxCaptureWorkers: lambdaMaxCaptureWorkers(),
+      interleaveCapture: true,
     });
     logEvent({
       event: "chunk_capture",

packages/producer/src/services/distributed/renderChunk.test.ts

@@ -55,6 +55,7 @@ import {
   CHUNK_INDEX_OUT_OF_RANGE,
   distributedCaptureSessionDependencies,
   extractDeferredVideoFramesForChunk,
+  interleavesCapture,
   MISSING_PLAN_ARTIFACT,
   MISSING_RUNTIME_ENV_SNAPSHOT,
   PLAN_HASH_MISMATCH,
@@ -1105,6 +1106,18 @@ describe("resolvePresetForLockedEncoder", () => {
   });
 });
 
+describe("interleavesCapture", () => {
+  it("is off for a caller that does not ask, so CPU-billed callers get contiguous ranges", () => {
+    expect(interleavesCapture(true, undefined)).toBe(false);
+    expect(interleavesCapture(true, { maxCaptureWorkers: 4 })).toBe(false);
+  });
+
+  it("is on only when the caller asks and the encoder overlaps", () => {
+    expect(interleavesCapture(true, { interleaveCapture: true })).toBe(true);
+    expect(interleavesCapture(false, { interleaveCapture: true })).toBe(false);
+  });
+});
+
 describe("resolveChunkCaptureWorkers", () => {
   it("keeps the machine-wide sizing when the runtime sets no budget", () => {
     expect(resolveChunkCaptureWorkers(121, 3, undefined)).toBe(3);

packages/producer/src/services/distributed/renderChunk.ts

@@ -221,6 +221,11 @@ export interface RenderChunkOptions {
    * this many, one browser per 20 frames; never lowers it.
    */
   maxCaptureWorkers?: number;
+  interleaveCapture?: boolean;
+}
+
+export function interleavesCapture(overlapping: boolean, options?: RenderChunkOptions): boolean {
+  return overlapping && options?.interleaveCapture === true;
 }
 
 /** A browser starts in about 3 s, a small share of 20 frames' capture. */
@@ -999,7 +1004,7 @@ export async function renderChunk(
             assertNotAborted: () => {},
             frameRange: range,
             onFrameLanded: (frame) => overlap.current?.onFrameLanded(frame),
-            interleaveFrames: overlap.current !== null,
+            interleaveFrames: interleavesCapture(overlap.current !== null, options),
           }).catch(async (captureError: unknown) => {
             await overlap.current?.abort();
             overlap.current = null;