javascript - Node FTP不执行 `once(' close')`下载文件大时的回调

Question

我有一种从 FTP 服务器下载文件的方法，它可以很好地处理较小的文件，但是当我用它来下载 ~5GB 大小的 zip 类型的文件时，它会下载它，但之后它什么都不做.当下载达到 100% 时，脚本不会继续。如果下载完成后它实际上在后台执行某些操作，我应该等待吗？有文件大小限制吗？

const FTP = require('ftp')

可在 npm 上找到

downloadFile: params => {
    return new Promise((resolve, reject) => {
      let ftpClient = new FTP()
      let total = params.state.fileSize
      let progress = 0
      ftpClient.on('ready', _ => {
        console.log(`Downloading ${params.targetedFile} ...`);
        ftpClient.get(params.targetedFile, (err, stream) => {
          if (err) reject(err)
          stream.on('data', buffer => {
            progress += buffer.length
            process.stdout.write(`Progress: ${(progress/total*100).toFixed(2)}% (${progress}/${total})  \r`)
          })
          stream.once('close', _ => {
            ftpClient.end()
            console.log(`Saved downloaded file to ${params.localDir}`);
            resolve(params.localDir)
          })
          stream.pipe(fs.createWriteStream(params.localDir))
        })
      })
      ftpClient.connect(params.auth)
    })
  }

基本上，下载大文件时不会执行 stream.once('close', ...) 的回调。并且它会针对相同类型的较小文件执行。

Answer 1

我建议您处理关闭写入流的事件。

原因很简单:我们从 ftp 的读取流和管道读取到写入流，一切正常，当文件成功关闭时。

所以代码:

downloadFile: params => {
    return new Promise((resolve, reject) => {
      let ftpClient = new FTP()
      let total = params.state.fileSize
      let progress = 0
      ftpClient.on('ready', _ => {
        console.log(`Downloading ${params.targetedFile} ...`);
        ftpClient.get(params.targetedFile, (err, stream) => {
          if (err) {
            ftpClient.end();
            return reject(err);
          }

          stream.on('data', buffer => {
            progress += buffer.length
            process.stdout.write(`Progress: ${(progress/total*100).toFixed(2)}% (${progress}/${total})  \r`)
          });

          // opening writeStream to file
          let finished = false;
          const writeStream = fs.createWriteStream(params.localDir);

          writeStream.on('finish', (result) => { // handling finish
            finished = true;
            ftpClient.end();
            console.log(`Finish triggered ${params.localDir}`);
            console.log(result);
            resolve(params.localDir);
          });

          writeStream.on('close', (result) => { // handling close
            ftpClient.end();
            console.log(`Close triggered ${params.localDir}`);
            console.log(result);
            resolve(params.localDir);
          })

          // piping readStream to writeStream
          stream.pipe(writeStream);
        })
      })
      ftpClient.connect(params.auth)
    })
  }