Merge pull request #1963 from Automattic/fix/1960-cloudflare-mutation-memory

Bound Cloudflare mutation memory

Author: chubes4

packages/runtime-cloudflare/src/mutation-memory.ts

@@ -0,0 +1,47 @@
+export const MUTATION_DIAGNOSTIC_SCHEMA = "wp-codebox/cloudflare-mutation-phase/v1"
+
+export class MutationRetainedBytes {
+  current = 0
+  peak = 0
+
+  retain(bytes: number): void {
+    this.current += bytes
+    this.peak = Math.max(this.peak, this.current)
+  }
+
+  release(bytes: number): void {
+    this.current -= bytes
+    if (this.current < 0) throw new Error("Mutation retained-byte accounting became negative.")
+  }
+}
+
+export interface MutationRetentionShape {
+  responseBytes: number
+  markdownBytes: number
+  uploadBytes: number
+  wpContentBytes: number
+  largestChangedFileBytes: number
+}
+
+export function mutationRetentionContract(shape: MutationRetentionShape): { wholeTreePeakBytes: number; incrementalPeakBytes: number } {
+  for (const value of Object.values(shape)) {
+    if (!Number.isSafeInteger(value) || value < 0) throw new Error("Mutation retention shape contains invalid bytes.")
+  }
+  return {
+    // The previous request retained the response, all three collections, and a hash copy of the active file.
+    wholeTreePeakBytes: shape.responseBytes + shape.markdownBytes + shape.uploadBytes + shape.wpContentBytes + shape.largestChangedFileBytes,
+    // Persistence owns one copied file; response conversion may briefly own both PHP and Fetch bodies.
+    incrementalPeakBytes: Math.max(shape.responseBytes + shape.largestChangedFileBytes, 2 * shape.responseBytes),
+  }
+}
+
+export function logMutationPhase(startedAt: number, phase: string, retained: MutationRetainedBytes, evidence: Record<string, number | string>): void {
+  console.log(JSON.stringify({
+    schema: MUTATION_DIAGNOSTIC_SCHEMA,
+    phase,
+    elapsedMs: Date.now() - startedAt,
+    retainedBytes: retained.current,
+    peakRetainedBytes: retained.peak,
+    ...evidence,
+  }))
+}