Node上的Fabric.js导致Heroku上的内存使用率达到512mb

Question

我在Heroku上有一个应用程序，我在其中生成一系列画布的PDF，但它经常超过512mb的内存配额，即使画布是空的。我认为问题出在canvas.loadFromJSON()这里是我使用的代码。任何帮助都非常感谢。

doc = new PDFDocument({size:[pageWidth, pageHeight]})

for (var i = 1; i < 9; i++) {
  canvas = new fabric.StaticCanvas()
  canvas.setWidth(canvasWidth)
  canvas.setHeight(canvasHeight)
  if ( publication && publication.pages.hasOwnProperty('p' + i) ) { // if not empty
    canvas.loadFromJSON(publication.pages['p' + i])
    delete publication.pages['p' + i]
    SVGtoPDF(doc, canvas.toSVG(), 0, 0)
    canvas.clear()
    canvas.dispose()
    if (i != 8) {
      doc.addPage()
    }
  }
  delete publication
  delete canvas
}

doc.pipe(res).on('finish', function() {
  console.log('single page pdf was successfully created by ' + process.pid)
})

doc.end()