使用NodeJS和ExressJS遇到503错误

Question

使用NodeJS时出现503错误。我的函数可以在localhost中工作，但在远程服务器上却收到503错误。

功能：

function postEdit(request, response) {
  var updatedParams = request.body.updatedParams,
      blockName     = request.params.blockname,
      primaryColor, secondaryColor, variables, scssStr;

  if (blockName === 'themeparam') {
    primaryColor = updatedParams.primary_color;
    secondaryColor = updatedParams.secondary_color;
    variables = updatedParams.variables;

    if (primaryColor || secondaryColor || variables) {

      scssStr = fs.readFileSync('./public/sass/_functions.scss', 'utf8');
      scssStr += fs.readFileSync('./public/sass/_settings.scss', 'utf8');

      if (primaryColor) {
        scssStr = scssStr.replace(/\$main-color:.+;/g, '$main-color: ' + primaryColor + ';');
      }

      if (secondaryColor) {
        scssStr = scssStr.replace(/\$secondary-color:.+;/g, '$secondary-color: ' + secondaryColor + ';');
      }

      scssStr += fs.readFileSync('./public/sass/app.scss', 'utf8');
      scssStr = scssStr.replace(/@import.+;/g, '');

      if (variables) {
        scssStr += variables;
      }

      fs.readdir('./public/sass/components', function(err, files) {

        files.forEach(function(file) {
          scssStr += fs.readFileSync('./public/sass/components/' + file, 'utf8');
        });

        fs.readdir('./public/sass/shortcodes', function(err, shortcodeFiles) {

          shortcodeFiles.forEach(function(shortcodeFile) {
            scssStr += fs.readFileSync('./public/sass/shortcodes/' + shortcodeFile, 'utf8');
          });

          fs.writeFileSync('./public/uploads/theme.scss', scssStr);

          sass.render({
            file: './public/uploads/theme.scss'
          }, function(err, result) {
            if (err) {
              console.log(err);
            }
            fs.writeFileSync('./public/uploads/theme.css', result.css);
          });
        });
      });
    } else {
      fs.stat('./public/uploads/theme.scss', function(err) {
        if (err) {
          console.log(err);
        }
        if (!err) {
          fs.unlinkSync('./public/uploads/theme.scss');
          fs.unlinkSync('./public/uploads/theme.css');
        }
      });
    }
  }

  if (blockName === 'robotparam') {
    fs.writeFileSync('./public/robots.txt', updatedParams.robot);
  }

  editJsonFile(request, response, './configs/options.json', function(options) {
    _.forEach(updatedParams, function(value, name) {
      var blockParam = _.find(options.blocks, { name: blockName }),
          param = _.find(blockParam.params, { name: name });
      param.value = value;
    });
  }, OptionController.baseUrl + '/edit/block/' + blockName);
}

function editJsonFile(request, response, jsonFile, updater, redirectUrl) {
  fs.readFile(jsonFile, 'utf8', function(err, data) {
    if (err) {
      throw err;
    }
    var options = JSON.parse(data);
    updater(options);
    fs.writeFile(jsonFile, JSON.stringify(options, null, 4), function(err) {
      if (err) {
        throw err;
      }
      request.flash('success', 'Done !');
      response.redirect(redirectUrl);
    });
  });
}

错误503：

Service Unavailable
The server is temporarily unable to service your request due to maintenance downtime or capacity problems. Please try again later.

Apache/2.4.7 (Ubuntu) Server at ****** Port 443

是否有解决方案来获取错误消息以查找问题？