Suspected memory leak

My server uses chartjs-node-canvas to generate many charts into a pdf. I ran the chrome heap profiler and noticed that each time I generate the report, I get a significant amount of chart related records with high retained sizes. Below are the screenshots:

Code usage:

rangeLine(min, max, value).then(chart => {
  ...
});

const rangeLine = (min, max, val) => {
  const canvasRenderService = new CanvasRenderService(170, 30);
  return canvasRenderService.renderToBuffer({
    type: "line",
    data: {
      datasets: [
        {
          pointBackgroundColor: "white",
          borderColor: "black",
          data: [
            {
              x: min,
              y: 0
            },
            {
              x: mid,
              y: 0
            },
            {
              x: max,
              y: 0
            }
          ]
        },
        {
          pointBackgroundColor: 'blue',
          pointRadius: 10,
          pointStyle: "rectRot",
          data: [
            {
              x: val,
              y: 0
            }
          ]
        }
      ]
    }
  });
};

Version: v2.4.0

[SeanSobey]

Hi seth.

freshRequire is needed to isolate canvas instances since actions in the library’s API mutate global state inside, canvas width and height for example. This way each CanvasRenderService encapsulates that state for you, at the cost of a bit of complexity with things like chart plugins, fonts etc.

The code you mention does actually appear like a bug, but could possibly be done that way for some reason. I will investigate more tomorrow to confirm but yeah looking at it I can’t think of why there would be separate instances for font and the canvas.

[seth2810]

Thank you, Sean.