Chore: add external download stat report

Build/lib/download-stats.ts

@@ -0,0 +1,143 @@
+import picocolors from 'picocolors';
+import { createPrettyBits, prettyBandwidth, prettyTraffic } from 'xbits';
+
+export type ExternalDownloadOutcome = 'winner' | 'aborted' | 'failed';
+
+export interface ExternalDownloadAttempt {
+  url: string,
+  kind: 'primary' | 'fallback',
+  outcome: ExternalDownloadOutcome,
+  startedAt: number,
+  headersAt: number | null,
+  bodyStartedAt: number | null,
+  endedAt: number,
+  bytes: number
+}
+
+export interface ExternalDownloadStatsSnapshot {
+  startedAt: number | null,
+  endedAt: number | null,
+  totalBytes: number,
+  usefulBytes: number,
+  wastedBytes: number,
+  winners: number,
+  aborted: number,
+  failed: number
+}
+
+function createEmptySnapshot(): ExternalDownloadStatsSnapshot {
+  return {
+    startedAt: null,
+    endedAt: null,
+    totalBytes: 0,
+    usefulBytes: 0,
+    wastedBytes: 0,
+    winners: 0,
+    aborted: 0,
+    failed: 0
+  };
+}
+
+let stats = createEmptySnapshot();
+const prettyBinaryByteSpeed = createPrettyBits({
+  bits: false,
+  binary: true,
+  speed: true,
+  largeK: true
+});
+
+export function downloadTimestamp() {
+  return performance.timeOrigin + performance.now();
+}
+
+export function formatDownloadSpeed(bytes: number, duration: number) {
+  if (duration <= 0) {
+    return 'n/a';
+  }
+  const bytesPerSecond = bytes / duration * 1000;
+  return `${prettyBinaryByteSpeed(bytesPerSecond)} (${prettyBandwidth(bytesPerSecond * 8)})`;
+}
+
+function formatDuration(duration: number | null) {
+  return duration == null ? 'n/a' : `${duration.toFixed(1)}ms`;
+}
+
+export function recordExternalDownloadAttempt(attempt: ExternalDownloadAttempt) {
+  stats.startedAt = stats.startedAt == null ? attempt.startedAt : Math.min(stats.startedAt, attempt.startedAt);
+  stats.endedAt = stats.endedAt == null ? attempt.endedAt : Math.max(stats.endedAt, attempt.endedAt);
+  stats.totalBytes += attempt.bytes;
+
+  if (attempt.outcome === 'winner') {
+    stats.winners++;
+    stats.usefulBytes += attempt.bytes;
+  } else {
+    stats.wastedBytes += attempt.bytes;
+    if (attempt.outcome === 'aborted') {
+      stats.aborted++;
+    } else {
+      stats.failed++;
+    }
+  }
+
+  const ttfb = attempt.headersAt == null ? null : attempt.headersAt - attempt.startedAt;
+  const queueWait = attempt.headersAt == null || attempt.bodyStartedAt == null
+    ? null
+    : attempt.bodyStartedAt - attempt.headersAt;
+  const bodyDuration = attempt.bodyStartedAt == null ? null : attempt.endedAt - attempt.bodyStartedAt;
+  const speed = bodyDuration == null ? 'n/a' : formatDownloadSpeed(attempt.bytes, bodyDuration);
+
+  console.log(
+    picocolors.gray('[external download]'),
+    attempt.kind,
+    attempt.outcome,
+    prettyTraffic(attempt.bytes),
+    speed,
+    `ttfb=${formatDuration(ttfb)}`,
+    `queue=${formatDuration(queueWait)}`,
+    attempt.url
+  );
+}
+
+export function mergeExternalDownloadStats(snapshot: ExternalDownloadStatsSnapshot | undefined) {
+  if (!snapshot) {
+    return;
+  }
+
+  if (snapshot.startedAt != null) {
+    stats.startedAt = stats.startedAt == null ? snapshot.startedAt : Math.min(stats.startedAt, snapshot.startedAt);
+  }
+  if (snapshot.endedAt != null) {
+    stats.endedAt = stats.endedAt == null ? snapshot.endedAt : Math.max(stats.endedAt, snapshot.endedAt);
+  }
+  stats.totalBytes += snapshot.totalBytes;
+  stats.usefulBytes += snapshot.usefulBytes;
+  stats.wastedBytes += snapshot.wastedBytes;
+  stats.winners += snapshot.winners;
+  stats.aborted += snapshot.aborted;
+  stats.failed += snapshot.failed;
+}
+
+export function takeExternalDownloadStats() {
+  const snapshot = stats;
+  stats = createEmptySnapshot();
+  return snapshot;
+}
+
+export function printExternalDownloadStats() {
+  if (stats.startedAt == null || stats.endedAt == null) {
+    return;
+  }
+
+  const duration = stats.endedAt - stats.startedAt;
+  console.log(
+    picocolors.bold('[external downloads total]'),
+    `useful=${prettyTraffic(stats.usefulBytes)}`,
+    `transferred=${prettyTraffic(stats.totalBytes)}`,
+    `hedge-waste=${prettyTraffic(stats.wastedBytes)}`,
+    `avg=${formatDownloadSpeed(stats.totalBytes, duration)}`,
+    `wall=${formatDuration(duration)}`,
+    `winner=${stats.winners}`,
+    `aborted=${stats.aborted}`,
+    `failed=${stats.failed}`
+  );
+}