Amazon web services – Lambda keeps consuming more and more memory until it kills itself

So I managed to narrow down the issue to the Konva library.

I found this issue: https://github.com/Automattic/node-canvas/issues/1974 and somebody commented with a link about node buffers. So I decided to test these parts.

First by purely allocating a buffer of the same size as what the image was:

const handler: APIGatewayProxyHandlerV2 = async event => {
     const before = process.memoryUsage();

const buffer = Buffer.alloc(4631);

     buffer.toString('base64'); 
     const after = process.memoryUsage(); 
    
    return { 
     statusCode: 200, 
     headers: { 'Content-Type': 'application/json', }, 
     body: JSON.stringify({ 
               before: before.rss / 1024 / 1024 + 'MB', 
               after: after.rss / 1024 / 1024 + 'MB', }), 
     }; 
 };

This resulted in no issues.

Next I tried with pure Konva (we use a modified version), because I found this: https://github.com/konvajs/konva/issues/1247

const handler: APIGatewayProxyHandlerV2 = async event => {

  const stage = new Konva.Stage({ width: 1080, height: 1080 }); 
  const buffer = (stage.toCanvas() as any as NodeCanvas).toBuffer(mimeType, { compressionLevel: 5, });

  buffer.toString('base64'); 

  //... rest omitted
};

Here the issue was back. Then I wanted to try using only node-canvas. Since the above issue mentioned leaks in that.

const handler: APIGatewayProxyHandlerV2 = async event => {

  const canvas = new NodeCanvas(1080, 1080, 'image'); 
  const buffer = canvas.toBuffer(mimeType, { compressionLevel: 5 });

  buffer.toString('base64'); 

  //... rest omitted
};

This didn't have the same issue. So Konva needed to be the culprit. I noticed in the above mentioned github issue, that they used stage.destroy() which I didn't do before. I simply added that and the issue seems to have gone away.

const handler: APIGatewayProxyHandlerV2 = async event => {

  const stage = new Konva.Stage({ width: 1080, height: 1080 }); 

  const buffer = (stage.toCanvas() as any as NodeCanvas).toBuffer(mimeType, { compressionLevel: 5, });

  stage.destroy() // This was the magic line

  buffer.toString('base64'); 

   //... rest omitted
};

I hope other in a similar situation can find this helpful. But thanks for all the suggestions!