Lambda Response size automatically exceeds more than 6MB in nodejs

Question

I have a lambda function,I get buffer from external api which is approximate 2.5 MB size but when I return same buffer in JSON object it becomes more than 7.5 MB, which is grater than lambda response size (6MB)limit,I am not sure how it is happening. Here is my code

module.exports.handler = (event, context, callback) => {
  const buffer = getAnswer();
  // This is approx 2.1 MB buffer size
  console.log(`Buffer size ${buffer.byteLength}`);

  const response = {
    headers: {
      'Content-Type': 'application/json',
    },
    isBase64Encoded: false,
    statusCode: 200,
    statusDescription: '200 OK',
    body: JSON.stringify(buffer),
  };
  // Here  size becomes more than 7.5 MB ,I am not sure how it happens
  console.log('This becomes 7.5 MB size', Buffer.byteLength(JSON.stringify(response)), 'bytes');
  context.succeed(response);// Gives error because it exceeds more than 6MB lambda response limit
};

score 2 · Answer 1 · answered Apr 29 '19 at 12:58

Inspect the result of JSON.stringify(buffer) and the reason will be obvious.

When you JSON.stringify a buffer the buffer is first converted to an object like this

{
  "type": "Buffer",
  "data": [byte0, byte1, byte2, byte3, .... ]
}

where byteX is the integer value of the byte.

If the buffer is text/JSON set the body to buffer.toString().

If you need to return binary consider adding a binary type to the rest api in ApiGateway and returning a base64 encoded version of the data.

Lambda Response size automatically exceeds more than 6MB in nodejs

1 Answers1