Initial open-source release

packages/cli/src/startup-profile.ts

@@ -0,0 +1,54 @@
+const enabled = process.env.KLO_PROFILE_STARTUP === '1' || process.env.KLO_PROFILE_STARTUP === 'true';
+const processStart = performance.now() - process.uptime() * 1000;
+
+interface StartupProfileEvent {
+  label: string;
+  at: number;
+  duration?: number;
+}
+
+const events: StartupProfileEvent[] = [];
+
+function now(): number {
+  return performance.now() - processStart;
+}
+
+export function profileMark(label: string): void {
+  if (!enabled) {
+    return;
+  }
+  events.push({ label, at: now() });
+}
+
+export async function profileSpan<T>(label: string, run: () => Promise<T>): Promise<T> {
+  if (!enabled) {
+    return await run();
+  }
+  const start = now();
+  try {
+    return await run();
+  } finally {
+    events.push({ label, at: start, duration: now() - start });
+  }
+}
+
+export function installStartupProfileReporter(): void {
+  if (!enabled) {
+    return;
+  }
+
+  process.once('beforeExit', () => {
+    const total = now();
+    process.stderr.write('\nKLO startup profile\n');
+    for (const event of events) {
+      const elapsed = event.at.toFixed(1).padStart(7);
+      if (event.duration === undefined) {
+        process.stderr.write(`${elapsed} ms  ${event.label}\n`);
+      } else {
+        const duration = event.duration.toFixed(1).padStart(7);
+        process.stderr.write(`${elapsed} ms  ${duration} ms  ${event.label}\n`);
+      }
+    }
+    process.stderr.write(`${total.toFixed(1).padStart(7)} ms  total\n`);
+  });
+}