将文件从 GCP 存储桶发送到第 3 方 pdf 转换器

问题描述

我正在尝试调整 Qwiklabs 教程以使用 pdfCrowd，而不是 LibreOffice。

该服务的工作原理是从一个 GCP 存储桶下载文件以进行“上传”，对其进行处理，然后将其上传到另一个用于“已处理”文件的存储桶，然后从“上传”存储桶中删除原始文件。

这是下载、上传、发送处理、然后删除的功能。这是来自 Qwiklabs 的代码，效果很好。

app.post('/',async (req,res) => {
  try {
    const file = decodeBase64Json(req.body.message.data);
    await downloadFile(file.bucket,file.name);
    const pdfFileName = await convertFile(file.name);
    await uploadFile(process.env.PDF_BUCKET,pdfFileName);
    await deleteFile(file.bucket,file.name);
  }
  catch (ex) {
    console.log(`Error: ${ex}`);
  }
  res.set('Content-Type','text/plain');
  res.send('\n\nOK\n\n');
})

原来的convertFile函数是：

    async function convertFile(fileName) {
      const cmd = 'libreoffice --headless --convert-to pdf --outdir /tmp ' +
                  `"/tmp/${fileName}"`;
      console.log(cmd);
      const { stdout,stderr } = await exec(cmd);
      if (stderr) {
        throw stderr;
      }
      console.log(stdout);
      pdfFileName = fileName.replace(/\.\w+$/,'.pdf');
      return pdfFileName;
}

当我更改我的 convertFile 函数时，问题就出现了。 LibreOffice 接受 file.name，但 pdfCrowd 需要文件路径。

所以我将 pdfCrowd 的函数更改为：

async function convertFile(fileName) {
    // create the API client instance
    const _newPdfPath = `/tmp/${fileName.replace(/\.\w+$/,'.pdf')}`
    const client = new pdfcrowd.HtmlToPdfClient("demo","ce544b6ea52a5621fb9d55f8b542d14d");
    // run the conversion and write the result to a file
    client.convertFileToFile(`/tmp/${fileName}`,_newPdfPath,function (err,fileName) {
        if (err)
            return console.error("Pdfcrowd Error: " + err);
        console.log("Success: the file was created " + fileName);
    });
    pdfFileName = fileName.replace(/\.\w+$/,'.pdf');
    return pdfFileName;
}

现在 pdf 转换返回 SUCCESS，但在收到通知后说没有我传递给 convertFileToFile 的“输出”文件路径中指定的文件或目录。 _newPdfPath 指定的文件不存在。

Error: Error: ENOENT: no such file or directory,stat '/tmp/mynew.pdf'
Success: the file was created /tmp/hello (31).pdf

pdfCrowd 函数应该是在 tmp 目录中创建一个文件，但是 async 是否正在等待在 tmp 目录中创建文件？

我的完整代码是：

const {promisify} = require('util');
const {Storage}   = require('@google-cloud/storage');
const exec        = promisify(require('child_process').exec);
const storage     = new Storage();
const express     = require('express');
const bodyParser  = require('body-parser');
const app         = express();

const pdfcrowd = require("pdfcrowd");

app.use(bodyParser.json());

const port = process.env.PORT || 8080;
app.listen(port,() => {
  console.log('Listening on port',port);
});

app.post('/',res) => {
  try {
    const file = decodeBase64Json(req.body.message.data);
    // console.log("FILE=========",file,req.body.message.data)
    await downloadFile(file.bucket,'text/plain');
  res.send('\n\nOK\n\n');
})

function decodeBase64Json(data) {
  return JSON.parse(Buffer.from(data,'base64').toString());
}

async function downloadFile(bucketName,fileName) {
  const options = {destination: `/tmp/${fileName}`};
  await storage.bucket(bucketName).file(fileName).download(options);
}

async function convertFile(fileName) {
    // create the API client instance
    const _newPdfPath = `/tmp/${fileName.replace(/\.\w+$/,'.pdf');
    return pdfFileName;
}

async function deleteFile(bucketName,fileName) {
  await storage.bucket(bucketName).file(fileName).delete();
}

async function uploadFile(bucketName,fileName) {
  await storage.bucket(bucketName).upload(`/tmp/${fileName}`);
}

解决方法

问题是您的 convertFile 函数在调用 convertFileToFile 回调之前完成。

我会将成功和错误的回调传递给convertFile，例如

app.post('/',async (req,res) => {
  try {
    const file = decodeBase64Json(req.body.message.data);
    // console.log("FILE=========",file,req.body.message.data)
    await downloadFile(file.bucket,file.name);
    let on_pdf_done = async function(pdfFileName) {
       await uploadFile(process.env.PDF_BUCKET,pdfFileName);
       await deleteFile(file.bucket,file.name);

       res.set('Content-Type','text/plain');
       res.send('\n\nOK\n\n');
    };
    let on_pdf_fail = function() {
       res.set('Content-Type','text/plain');
       res.send('\n\nERROR\n\n');
    };
    convertFile(file.name,on_pdf_done,on_pdf_fail);    
  }
  catch (ex) {
    console.log(`Error: ${ex}`);
  }
})

function convertFile(fileName,success_callback,fail_callback) {
    // create the API client instance
    const _newPdfPath = `/tmp/${fileName.replace(/\.\w+$/,'.pdf')}`
    const client = new pdfcrowd.HtmlToPdfClient("demo","ce544b6ea52a5621fb9d55f8b542d14d");
    // run the conversion and write the result to a file
    client.convertFileToFile(`/tmp/${fileName}`,_newPdfPath,function (err,fileName) {
        if (err)
            return fail_callback();
        success_callback(fileName.replace(/\.\w+$/,'.pdf'));
    });
}