php shell_exec 不适用于 puppeteer

• 网络服务器：nginx
• PHP 框架：Laravel 5.5
• 生成PDF的库：puppeteer

所以我想要做的是，当用户单击下载按钮时，服务器将执行以下操作：

1. 构造一个包含内容的 HTML 文件
2. 运行以下代码

Laravel 控制器

$shell_output = shell_exec('`which node` ' . base_path('bin/export.js') . ' ' . $html_file . ' ' . $pdf_file . ' A4');
print($shell_output); // <------- empty output

$workable_output = shell_exec('echo `which node`');
print($shell_output); // <------- THIS IS SHOWING "/usr/local/bin/node"

该export.js内容

const puppeteer = require('puppeteer');

var filename = process.argv[2];
var output = process.argv[3];

(async () => {
  const browser = await puppeteer.launch();
  const page = await browser.newPage();
  await page.setViewport({ width: 1000, height: 1415 });
  await page.goto('file://' + filename, { waitUntil: 'networkidle2' });
  await page.emulateMedia('print');
  await page.pdf({
    path: output,
    format: 'A4',
    printBackground: true,
    landscape: false,
    margin: {
      top: '60px',
      right: '20px',
      bottom: '30px',
      left: '20px'
    }
  });

  await browser.close();
})();

但问题是，没有生成PDF文件，而且$shell_output也是空的。

然后我尝试在终端中运行 shell 命令，它运行良好。IE

$ `which node` export.js content.html content.pdf A4

再次，我尝试创建一个 php 文件，并使用 php-cli 运行，即

$ php test.php

test.php的内容如下

<?php
$shell_output = shell_exec('env DEBUG="puppeteer:*" `which node` export.js content.html content.pdf A4');
echo $shell_output;

服务器日志

/var/log/nginx/error.log

2018/03/13 10:37:05 [error] 13017#13017: send() failed (111: Connection refused) while resolving, resolver: 127.0.0.1:53

P/S：我托管在 AWS EC2 中。当我在本地机器上运行时，这没有问题。

更新于 2018-03-14 14:55PM (UTC+8)

我试图将代码放入 Laravel 中的测试文件夹

./tests/Unit/ExampleTest.php

$shell_output = shell_exec('`which node` ' . base_path('bin/export.js') . ' ' . $html_file . ' ' . $pdf_file . ' A4');

并与ubuntu用户一起运行，它可以工作

ubuntu@ip-xxx-xx-xx-xx:/var/www/project$ ./vendor/phpunit/phpunit/phpunit --filter ExampleTest
PHPUnit 6.3.0 by Sebastian Bergmann and contributors.

.
.                                                                  2 / 2 (100%)

Time: 4.82 seconds, Memory: 14.00MB

但是，当我尝试使用www-data用户运行时，它失败了

ubuntu@ip-xxx-xx-xx-xx:/var/www/project$ sudo -u www-data ./vendor/phpunit/phpunit/phpunit --filter ExampleTest
PHPUnit 6.3.0 by Sebastian Bergmann and contributors.

.(node:7991) UnhandledPromiseRejectionWarning: Error: spawn EACCES
    at ChildProcess.spawn (internal/child_process.js:330:11)
    at Object.exports.spawn (child_process.js:500:9)
    at Function.launch (/var/www/project/node_modules/puppeteer/lib/Launcher.js:106:40)
    at <anonymous>
(node:7991) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
(node:7991) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
.                                                                  2 / 2 (100%)

Time: 276 ms, Memory: 14.00MB

OK (2 tests, 2 assertions)

知道问题出在哪里吗？