Ubuntu Docker环境下用html-pdf npm包生成PDF时出现EPIPE错误

本地Windows和Mac系统中正常运行的HTML转PDF功能，在Ubuntu Docker环境下使用html-pdf npm包时抛出Error: write EPIPE错误，以下是详细信息：

错误日志 #

node:events:491

      throw er; // Unhandled 'error' event

      ^

Error: write EPIPE

    at afterWriteDispatched (node:internal/stream_base_commons:160:15)

    at writeGeneric (node:internal/stream_base_commons:151:3)

    at Socket._writeGeneric (node:net:905:11)

    at Socket._write (node:net:917:8)

    at writeOrBuffer (node:internal/streams/writable:391:12)

    at _write (node:internal/streams/writable:332:10)

    at Socket.Writable.write (node:internal/streams/writable:336:10)

    at PDF.PdfExec [as exec] (/usr/src/node-app/node_modules/html-pdf/lib/pdf.js:156:15)

    at PDF.PdfToStream [as toStream] (/usr/src/node-app/node_modules/html-pdf/lib/pdf.js:59:8)

    at /usr/src/node-app/server.js:335:75

Emitted 'error' event on Socket instance at:

    at emitErrorNT (node:internal/streams/destroy:157:8)

    at emitErrorCloseNT (node:internal/streams/destroy:122:3)

    at processTicksAndRejections (node:internal/process/task_queues:83:21) {

  errno: -32,

  code: 'EPIPE',

  syscall: 'write'

Docker操作系统信息 #

uname -a
[1670850844595]     Linux 693e0a6af7a3 4.14.281-212.502.amzn2.x86_64 #1 SMP Thu May 26 09:52:17 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux

尝试的代码 #

试过两个API，均出现相同错误：

1. toStream方式：

htmlPdf.create(htmlContent, htmlToPdfOptions).toStream(function(err: any, stream: { pipe: (arg0: fs.WriteStream) => void; }{
        stream.pipe(fs.createWriteStream('./outputDir/chatTranscript.pdf'));
       });

2. toFile方式：

htmlPdf.create(htmlContent, htmlToPdfOptions)
      .toFile("newPdf.pdf", function(err: any, result: any) {
        if (err) { console.log("Error while generating pdf file - ",err); }
      //     console.log("pdf file generated - ",result);
      //     return; 
     });

完整方法代码 #

async function generatePdf() {
  try {
    console.log("Inside generatePdf() ...")
      let  HTMLFilePath = __dirname+"/pdfTemplate.html";

      if (!fs.existsSync(HTMLFilePath)) {
          console.log("file doesn't exists");
      } else {
        console.log("file exists: ",HTMLFilePath);
      }

      const htmlContent = fs.readFileSync(HTMLFilePath, 'utf8');
      const htmlToPdfOptions = {
          "type": ".pdf",
          "height": "650px",
          "width": "850px",
          "renderDelay": 2000,
      };

       const a = await htmlPdf.create(htmlContent, htmlToPdfOptions).toStream(function(err: any, stream: { pipe: (arg0: fs.WriteStream) => void; }{
        stream.pipe(fs.createWriteStream('./outputDir/chatTranscript.pdf'));
       });

       console.log("printing output of html stream");
       console.log("a: ",a);
       return a;

      // htmlPdf.create(htmlContent, htmlToPdfOptions)
      // .toFile("newPdf.pdf", function(err: any, result: any) {
      //     if (err) {
      //       console.log("Error while generating pdf file - ",err);
      //     } 
      //     console.log("pdf file generated - ",result);
      //     return; 
      // });
  } catch (error) {
      console.log("error while converting html-to-pdf", error);
  }
}

已做排查 #

• 之前容器提示缺失libfontconfig库，已在Dockerfile中添加：

apt-get update
apt-get install -y libfontconfig

• 确认PDF生成目录拥有写入权限。

解决方案 #

1. 补充安装PhantomJS依赖组件 #

html-pdf依赖PhantomJS运行，Docker的Ubuntu镜像仅安装libfontconfig不足以满足运行需求，需补充安装底层依赖：

apt-get install -y libfreetype6 libx11-6 libxext6 libxrender1 fontconfig

将上述命令添加到Dockerfile中，重新构建镜像。

2. 指定兼容的PhantomJS版本 #

html-pdf内置的PhantomJS版本可能与Linux内核（你的内核为4.14）不兼容，可单独安装指定版本的phantomjs-prebuilt：

npm install phantomjs-prebuilt@2.1.16 --save

然后在代码中配置html-pdf使用该本地版本：

const htmlPdf = require('html-pdf');
const phantomPath = require('phantomjs-prebuilt').path;

const htmlToPdfOptions = {
    "type": ".pdf",
    "height": "650px",
    "width": "850px",
    "renderDelay": 2000,
    "phantomPath": phantomPath // 添加此配置项
};

3. 完善流的错误处理 #

原代码未监听流的错误事件，导致未捕获异常抛出，修改toStream调用逻辑：

htmlPdf.create(htmlContent, htmlToPdfOptions).toStream(function(err: any, stream: { pipe: (arg0: fs.WriteStream) => void; }{
    if (err) {
        console.error('Stream生成错误:', err);
        return;
    }
    const writeStream = fs.createWriteStream('./outputDir/chatTranscript.pdf');
    stream.pipe(writeStream);
    // 监听文件写入错误
    writeStream.on('error', (err) => {
        console.error('PDF写入错误:', err);
    });
    // 监听写入完成事件
    writeStream.on('finish', () => {
        console.log('PDF生成成功');
    });
});

4. 修正async/await与回调混用问题 #

原代码中await调用基于回调的toStream方法无效，会导致流程异常，改用Promise包装实现异步等待：

// 封装toStream为Promise
function generatePdfStream(htmlContent, options) {
    return new Promise((resolve, reject) => {
        htmlPdf.create(htmlContent, options).toStream((err, stream) => {
            if (err) reject(err);
            else resolve(stream);
        });
    });
}

// 在generatePdf函数中使用
async function generatePdf() {
  try {
    // ... 省略其他代码 ...
    const stream = await generatePdfStream(htmlContent, htmlToPdfOptions);
    const writeStream = fs.createWriteStream('./outputDir/chatTranscript.pdf');
    stream.pipe(writeStream);
    // 等待写入完成
    await new Promise((resolve, reject) => {
        writeStream.on('finish', resolve);
        writeStream.on('error', reject);
    });
    console.log('PDF生成成功');
    return;
  } catch (error) {
      console.log("html转PDF失败", error);
  }
}

内容的提问来源于stack exchange，提问作者Hemant