Steaming Lambda Function "setContentType is not a function"

[andreaselia]

I'm attempting to stream data using my Lambda function deployed using sls deploy and the below configuration, but no matter what I do, there's always an issue with things not existing on the responseStream such as setContentType.

Any help or advice would be greatly appreciated. I've spent a couple of days researching but haven't really found anything that has helped here.

Example:

exports.handler = awslambda.streamifyResponse(
    async (event, responseStream, context) => {
        responseStream.setContentType('text/plain');
        responseStream.write('Hello, world!');
        responseStream.end();
    }
);

My serverless.yml file:

app: sls
service: sls
frameworkVersion: '3'

provider:
  name: aws
  runtime: nodejs18.x
  region: eu-west-1
  timeout: 30

functions:
  api:
    handler: index.handler
    layers:
      - !Ref ApiLambdaLayer
    url:
      invokeMode: RESPONSE_STREAM
    events:
      - httpApi:
          path: /
          method: get

layers:
  api:
    package:
      artifact: ./resources.zip

[LewisW]

I have this same error for a non-function URL based lambda but in your case, for function url based lambdas, you need to call:

                const metadata = {
                    statusCode: 200,
                    headers: {
                        "Content-Type": "application/json",
                    }
                };
                
                // Assign to the responseStream parameter to prevent accidental reuse of the non-wrapped stream.
                responseStream = awslambda.HttpResponseStream.from(responseStream, metadata);
                

See: https://docs.aws.amazon.com/lambda/latest/dg/response-streaming-tutorial.html#response-streaming-tutorial-create-function-cfn

[andreaselia]

Ah, I see, thanks for that - I'll try and give it a go in the coming day or so and update this discussion.

[LewisW]

If you're still having issues, try another region. I couldn't get it working in us-east-1 no how many hours I wasted but us-east-2 worked straight away.

[andreaselia]

Thanks mate. I read another thread on that too, I've been trying with eu-west-1 and eu-west-2, but didn't do too much more than the basic test now as I've been setting things up manually via the AWS console instead of using Serverless. I'll give Serverless another try soon though and see if I can move my setup there.

Do you have your streaming working on Serverless now?

[padargyula81]

Hi!

What should I do to be able to use the "awslambda" object/package/whatever? What is it? If I type it, it is unknown, and I find nothing about it.

Thanks!

[IlmariKu]

Yeah, I've had the same issue and I've disabled Typescript for it. It seems to be some runtime-injected dependency

[LewisW]

You can use this library to handle missing types (and local testing): https://github.com/astuyve/lambda-stream