与外部程序之间的流式传输需要使用javascript节点的文件

问题：

我需要上传数百个PDF文档，将它们转换为HTML，然后将HTML存储在MongoDB中。我目前正在文件系统中保存传入的PDF文档和转换的HTML。有没有一种方法可以使用流来避免所有的文件I/O

当前方法（有效但速度较慢）：

我正在使用：

巴士男孩阅读上传的PDF文件，我保存到文件系统

我在node.js中创建了一个“exec”子进程，该子进程调用“'pdftohtml-c-s-noframes-nodrm'+inputFileNamePDF+''+outputFileNameHTML”。HTML输出文件将保存到文件系统中

然后，我遍历所有HTML文件，创建一个到MongoDB的批量升级

理想情况下，我希望将上传的PDF文件直接流式传输到“inputFileNamePDF”。然后将转换后的“outputFileNameHTML”流式传输到大容量upsert

代码如下：

    var path = require("path"),
    Busboy = require('busboy')
    http = require('http'),
    util = require('util'),
    fs = require('fs-extra'),
    pdftohtml = require('pdftohtmljs'),
    exec =require('child_process').exec,
    pdf_extract = require('pdf-extract'),

exports.postUpload = function (req, res) {
  // parse a file upload
  var fileName = "";
  var uploadDir = '/tmp/' + res.locals.user._doc.email.replace(/[@\.]/g,"_");

  var infiles = 0, outfiles = 0, done = false,
  busboy = new Busboy({ headers: req.headers });
  console.log('Start parsing form ...');
  busboy.on('file', function (fieldname, file, filename) {
      ++infiles;
      console.log("file event #" + infiles);
      onFile(fieldname, file, filename, function () {
          ++outfiles;
          console.log("file #" + infiles + " written.");
          if (done) console.log(outfiles + '/' + infiles + ' parts written to disk');
          if (done && infiles === outfiles) {
              // ACTUAL EXIT CONDITION
              console.log('All parts written to disk');
              res.writeHead(200, { 'Connection': 'close' });
              res.end("That's all folks!");
              convertToHTMLTxt();
          }
      });
  });
  busboy.on('finish', function () {
      console.log('Done parsing form!');
      done = true;
  });
  req.pipe(busboy);

function onFile(fieldname, file, filename, next) {
    // or save at some other location
    var fileName = "";
    fileName = filename.replace( /[^a-z0-9_\-]/gi,"_");
    fileName = fileName.replace(/_(pdf|docx|doc)$/i,".$1");
    var fstream = fs.createWriteStream(path.join(uploadDir, fileName));
    file.on('end', function () {
        console.log(fieldname + '(' + fileName + ') EOF');
    });
    fstream.on('close', function () {
        console.log(fieldname + '(' + fileName + ') written to disk');
        next();
    });
    console.log(fieldname + '(' + fileName + ') start saving');
    file.pipe(fstream);
}  

  function convertToHTMLTxt () {
    var execTxt, execHTML, execPDF;
    var textDir = 'text';
    var htmlDir = 'html';

    console.log('Directory: ', uploadDir);
    fs.readdir(uploadDir, function(err, files) {
      if (err) {
        console.log('error reading directory: ', uploadDir);
        return;
      }

      files.forEach(function(fileName) {
        var fileNameHTML = path.join(uploadDir, htmlDir,
          fileName.replace(/(pdf|docx|doc)$/i,"html"));
        var fileNamePDF = path.join(uploadDir, fileName);

        if (fileName.match(/pdf$/i)) {
          execPDF = exec('pdftohtml -c -s -noframes -nodrm ' 
                         + fileNamePDF + ' ' + fileNameHTML,
            function(error, stdout, stderr) {
              console.log('stdout: ', stdout);
              console.log('stderr: ', stderr);
              if (error !== null) {
                  console.log('exec error: ', error);
              }
          });

          execPDF.on('close', function (code) {
            console.log('******** PDF to HTML Conversion complete - exit code ' 
              + code);
          });

        }
      })
    });

转换完成后，我迭代所有HTML文件并执行MongoDB批量升级：

          fs.readFile(fileNameHTML, 'utf8', function (err, HTMLData) {
            if (err) {
              console.log('error reading file: ', fileNameHTML + '/nerror: ' + err);
              callback(err);
              return;
            } 
            bulk.find({ userName: userName,
                         docName : fileName
                      }).upsert()
            .updateOne({userName: userName,
                     docName : fileName, 
                     HTMLData : HTMLData});