feat!: use inspector for time profiles

Author: aabmass

ts/src/index.ts

@@ -37,12 +37,16 @@ export const heap = {
 
 // If loaded with --require, start profiling.
 if (module.parent && module.parent.id === 'internal/preload') {
-  const stop = time.start();
-  process.on('exit', () => {
-    // The process is going to terminate imminently. All work here needs to
-    // be synchronous.
-    const profile = stop();
-    const buffer = encodeSync(profile);
-    writeFileSync(`pprof-profile-${process.pid}.pb.gz`, buffer);
+  time.start().then(stop => {
+    process.on('exit', async () => {
+      // The process is going to terminate imminently. All work here needs to
+      // be synchronous.
+
+      // TODO: this code no longer works because stop() cannot be run synchronously. Maybe
+      // beforeExit event would be a decent middleground, or can run this in a signal handler.
+      const profile = await stop();
+      const buffer = encodeSync(profile);
+      writeFileSync(`pprof-profile-${process.pid}.pb.gz`, buffer);
+    });
   });
 }

ts/src/time-profiler-inspector.ts

@@ -0,0 +1,113 @@
+/**
+ * Copyright 2018 Google Inc. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import {TimeProfile, TimeProfileNode} from './v8-types';
+import * as inspector from 'node:inspector';
+
+const session = new inspector.Session();
+session.connect();
+
+// Wrappers around inspector functions
+export function startProfiling(): Promise<void> {
+  return new Promise<void>((resolve, reject) => {
+    session.post('Profiler.enable', err => {
+      if (err !== null) {
+        reject(err);
+      }
+      session.post('Profiler.start', err => {
+        if (err !== null) {
+          reject(err);
+        }
+        resolve();
+      });
+    });
+  });
+}
+
+export function stopProfiling(): Promise<TimeProfile> {
+  // return profiler.timeProfiler.stopProfiling(runName, includeLineInfo || false);
+  return new Promise<TimeProfile>((resolve, reject) => {
+    session.post('Profiler.stop', (err, {profile}) => {
+      if (err !== null) {
+        reject(err);
+      }
+      resolve(translateToTimeProfile(profile));
+    });
+  });
+}
+
+function translateToTimeProfile(
+  profile: inspector.Profiler.Profile
+): TimeProfile {
+  const root: inspector.Profiler.ProfileNode | undefined = profile.nodes[0];
+  // Not sure if this could ever happen...
+  if (root === undefined) {
+    return {
+      endTime: profile.endTime,
+      startTime: profile.startTime,
+      topDownRoot: {
+        children: [],
+        hitCount: 0,
+        scriptName: '',
+      },
+    };
+  }
+
+  const nodesById: {[key: number]: inspector.Profiler.ProfileNode} = {};
+  profile.nodes.forEach(node => (nodesById[node.id] = node));
+
+  function translateNode({
+    hitCount,
+    children,
+    callFrame: {columnNumber, functionName, lineNumber, scriptId, url},
+  }: inspector.Profiler.ProfileNode): TimeProfileNode {
+    const parsedScriptId = parseInt(scriptId);
+    return {
+      name: functionName,
+      scriptName: url,
+
+      // Add 1 because these are zero-based
+      columnNumber: columnNumber + 1,
+      lineNumber: lineNumber + 1,
+
+      hitCount: hitCount ?? 0,
+      scriptId: Number.isNaN(parsedScriptId) ? 0 : parsedScriptId,
+      children:
+        children?.map(childId => translateNode(nodesById[childId])) ?? [],
+    };
+  }
+
+  return {
+    endTime: profile.endTime,
+    startTime: profile.startTime,
+    topDownRoot: translateNode(root),
+  };
+}
+
+export function setSamplingInterval(intervalMicros: number): Promise<void> {
+  return new Promise<void>((resolve, reject) => {
+    session.post(
+      'Profiler.setSamplingInterval',
+      {interval: intervalMicros},
+      err => {
+        if (err !== null) {
+          reject(err);
+        }
+        resolve();
+      }
+    );
+  });
+}

ts/src/time-profiler.ts

@@ -22,7 +22,7 @@ import {
   setSamplingInterval,
   startProfiling,
   stopProfiling,
-} from './time-profiler-bindings';
+} from './time-profiler-inspector';
 
 let profiling = false;
 
@@ -49,40 +49,36 @@ export interface TimeProfilerOptions {
 }
 
 export async function profile(options: TimeProfilerOptions) {
-  const stop = start(
+  const stop = await start(
     options.intervalMicros || DEFAULT_INTERVAL_MICROS,
-    options.name,
-    options.sourceMapper,
-    options.lineNumbers
+    options.sourceMapper
   );
   await delay(options.durationMillis);
-  return stop();
+  return await stop();
 }
 
-export function start(
+export async function start(
   intervalMicros: Microseconds = DEFAULT_INTERVAL_MICROS,
-  name?: string,
-  sourceMapper?: SourceMapper,
-  lineNumbers?: boolean
+  sourceMapper?: SourceMapper
 ) {
   if (profiling) {
     throw new Error('already profiling');
   }
 
   profiling = true;
-  const runName = name || `pprof-${Date.now()}-${Math.random()}`;
-  setSamplingInterval(intervalMicros);
+  await setSamplingInterval(intervalMicros);
   // Node.js contains an undocumented API for reporting idle status to V8.
   // This lets the profiler distinguish idle time from time spent in native
   // code. Ideally this should be default behavior. Until then, use the
   // undocumented API.
   // See https://github.com/nodejs/node/issues/19009#issuecomment-403161559.
   // eslint-disable-next-line @typescript-eslint/no-explicit-any
   (process as any)._startProfilerIdleNotifier();
-  startProfiling(runName, lineNumbers);
-  return function stop() {
+  await startProfiling();
+  return async function stop() {
     profiling = false;
-    const result = stopProfiling(runName, lineNumbers);
+    const result = await stopProfiling();
+    console.log(JSON.stringify(result));
     // eslint-disable-next-line @typescript-eslint/no-explicit-any
     (process as any)._stopProfilerIdleNotifier();
     const profile = serializeTimeProfile(result, intervalMicros, sourceMapper);