v8.writeHeapSnapshot([filename[,options]])


  • filename <string> 要保存 V8 堆快照的文件路径。如果不指定,则会生成格式为 'Heap-${yyyymmdd}-${hhmmss}-${pid}-${thread_id}.heapsnapshot' 的文件名,其中 {pid} 是 Node.js 进程的 PID,当 writeHeapSnapshot() 从 Node.js 主线程调用时,{thread_id} 将是 0 或工作线程的 id。

    ¥filename <string> The file path where the V8 heap snapshot is to be saved. If not specified, a file name with the pattern 'Heap-${yyyymmdd}-${hhmmss}-${pid}-${thread_id}.heapsnapshot' will be generated, where {pid} will be the PID of the Node.js process, {thread_id} will be 0 when writeHeapSnapshot() is called from the main Node.js thread or the id of a worker thread.

  • options <Object>

    • exposeInternals <boolean> 如果为真,则在堆快照中公开内部结构。默认值:false

      ¥exposeInternals <boolean> If true, expose internals in the heap snapshot. Default: false.

    • exposeNumericValues <boolean> 如果为真,则在人工字段中公开数值。默认值:false

      ¥exposeNumericValues <boolean> If true, expose numeric values in artificial fields. Default: false.

  • 返回:<string> 保存快照的文件名。

    ¥Returns: <string> The filename where the snapshot was saved.

生成当前 V8 堆的快照并将其写入 JSON 文件。此文件旨在与 Chrome 开发者工具等工具一起使用JSON 模式未记录并且特定于 V8 引擎,并且可能会从 V8 的一个版本更改为下一个版本。

¥Generates a snapshot of the current V8 heap and writes it to a JSON file. This file is intended to be used with tools such as Chrome DevTools. The JSON schema is undocumented and specific to the V8 engine, and may change from one version of V8 to the next.

堆快照特定于单个 V8 隔离。使用 工作线程 时,从主线程生成的堆快照将不包含有关工作进程的任何信息,反之亦然。

¥A heap snapshot is specific to a single V8 isolate. When using worker threads, a heap snapshot generated from the main thread will not contain any information about the workers, and vice versa.

创建堆快照需要的内存大约是创建快照时堆大小的两倍。这会导致 OOM 杀手终止进程的风险。

¥Creating a heap snapshot requires memory about twice the size of the heap at the time the snapshot is created. This results in the risk of OOM killers terminating the process.

生成快照是一个同步的操作,它会根据堆大小在一段时间内阻塞事件循环。

¥Generating a snapshot is a synchronous operation which blocks the event loop for a duration depending on the heap size.

const { writeHeapSnapshot } = require('node:v8');
const {
  Worker,
  isMainThread,
  parentPort,
} = require('node:worker_threads');

if (isMainThread) {
  const worker = new Worker(__filename);

  worker.once('message', (filename) => {
    console.log(`worker heapdump: ${filename}`);
    // Now get a heapdump for the main thread.
    console.log(`main thread heapdump: ${writeHeapSnapshot()}`);
  });

  // Tell the worker to create a heapdump.
  worker.postMessage('heapdump');
} else {
  parentPort.once('message', (message) => {
    if (message === 'heapdump') {
      // Generate a heapdump for the worker
      // and return the filename to the parent.
      parentPort.postMessage(writeHeapSnapshot());
    }
  });
}