v8 getHeapShot使人捉弄不清

Question

目前，我的代码中有一个内存泄漏，我试图通过使用节点v8库创建堆快照来调试它。我正在使用express在类型记录中创建端点，我可以调用它，它应该返回一个JSON对象，该对象可以写到文件中并导入到chrome工具中。

但是，当我运行我的jest测试来测试端点时，它将无限期挂起。我正在打电话

jest --runInBand InfoController.test.ts

InfoController.ts

import { Router } from 'express';
import { getHeapSnapshot } from 'v8';
import { constants } from 'http2';

export const InfoController = (): Router => {
  const router = Router();
  router.get('/heapdump', (_, res) => {
    console.log('requesting heap snapshot')
    const heapShot = getHeapSnapshot();
    console.log('heap');
    let data = '';
    heapShot.on('readable', () => {
      const chunk = heapShot.read();
      while (chunk !== null) {
        data += chunk;
      }
    });

    heapShot.on('end', () => res.status(constants.HTTP_STATUS_OK).json(JSON.parse(data)));
  });

  return router;
};

InfoController.test.ts

import express from 'express';
import { constants as httpConstants } from 'http2';
import Request from 'supertest';
import { InfoController } from './InfoController';

describe(' InfoController', () => {
  describe('GET /heapdump', () => {
    test('should be able to retrieve a v8 heapdump of the service', async () => {
      const controller = InfoController();

      const app = express();
      app.use(express.json());
      app.use(controller);

      const result = await Request(app).get('/heapdump').expect(httpConstants.HTTP_STATUS_OK);
      console.log(result.body);
    });
  });
});

jest.config.js

module.exports = {
  preset: 'ts-jest',
  bail: true,
  verbose: true,
  testEnvironment: 'node',
  collectCoverage: false,
  testMatch: ['**/**/*.test.ts'],
  testPathIgnorePatterns: ['<rootDir>/node_modules/', '<rootDir>/build/'],
  collectCoverageFrom: ['<rootDir>/src/**', '!<rootDir>/src/index.ts'],
  coveragePathIgnorePatterns: ['<rootDir>/node_modules', '<rootDir>/__tests__'],
  globalSetup: '<rootDir>/__tests__/global/setup.ts',
};

这是我得到的输出

$ jest --runInBand src/http/controllers/InfoController.test.ts
console.log
    requesting heap snapshot

      at src/http/controllers/InfoController.ts:8:13


 RUNS  src/http/controllers/InfoController.test.ts

在这之后，它只是挂着，永远不会完成？

Answer 1

考虑一下代码中心的这个片段：

      const chunk = heapShot.read();
      while (chunk !== null) {
        data += chunk;
      }

如果chunk永远是非空的(这几乎是肯定会发生的)，那么这个循环将永远循环(或者，至少，直到data变得如此大，整个进程都会与OOM崩溃)。

正式文件展示了如何修改代码片段以使其工作的一种可能性：

  let chunk;
  while ((chunk = heapShot.read()) !== null) {
    data += chunk;
  }