Unclear how to configure binary content types

[AndrejMitrovic]

Hi.

For serverless lambdas in micronaut-aws, the MicronautResponseWriter class will base-64 encode the response and set isBase64Encoded to true in the response JSON object so the AWS API Gateway can handle it:

micronaut-aws/function-aws-api-proxy/src/main/java/io/micronaut/function/aws/proxy/MicronautResponseWriter.java

Lines 90 to 95 in 1c52abe

	if (containerResponse.isBinary(containerResponse.getContentType().map(Object::toString).orElse(null))) {
	byte[] bytes = outputStream.toByteArray();
	awsProxyResponse.setBody(
	Base64.getMimeEncoder().encodeToString(bytes)
	);
	awsProxyResponse.setBase64Encoded(true);

I'm trying to figure out how to tell MicronautResponseWriter that my response body really is binary (it's gzipped).

I see the isBinary() check is implemented here:

micronaut-aws/function-aws-api-proxy/src/main/java/io/micronaut/function/aws/proxy/MicronautAwsProxyResponse.java

Lines 202 to 212 in 1c52abe

	boolean isBinary(String contentType) {
	if (contentType != null) {
	int semidx = contentType.indexOf(';');
	if (semidx >= 0) {
	return MicronautLambdaContainerHandler.getContainerConfig().isBinaryContentType(contentType.substring(0, semidx));
	} else {
	return MicronautLambdaContainerHandler.getContainerConfig().isBinaryContentType(contentType);
	}
	}
	return false;
	}

It seems to check the content-type from the response header and then compare it to the container config's known binary content types. But how do I set these known binary content types?

I was hoping to do something like this in my controller:

@Get("some/endpoint")
public HttpResponse<String> someEndpoint() {
    var gzippedBytes = ...;
    return HttpResponse.ok(gzippedBytes)
                       .contentType(MediaType.APPLICATION_JSON);
}

And then set "application/json" as a binary content type in the config. This should hopefully make micronaut base-64 encode the string and return something like this to AWS API Gateway:

        return {
            'headers': { "Content-Type": "application/json" },
            'statusCode': 200,
            'body': base64.b64encode(<actual-binary-data>).decode('utf-8'),
            'isBase64Encoded': True
        }

Above taken from: https://docs.amazonaws.cn/en_us/apigateway/latest/developerguide/lambda-proxy-binary-media.html

---

The actual problem I'm trying to solve: Our lambda return payloads exceed 6MiB - the maximum Lambda payloads allowed by AWS. Gzipping helps us reduce our payloads a lot (our data is mostly textual). However we're struggling to understand how to tell micronaut to treat the return payload as binary, so it will create the JSON object above and pass that on to AWS.

[AndrejMitrovic]

I've managed to make it work by setting the contentType to "application/zip". It seems to trigger the config here:

micronaut-aws/function-aws-api-proxy/src/main/java/io/micronaut/function/aws/proxy/AbstractLambdaContainerHandler.java

Line 110 in 1c52abe

config.addBinaryContentTypes("application/zip");

Although I've tried also doing config.addBinaryContentTypes("application/json");, that didn't work. Haven't had a chance to debug that yet.

For now this solution works for me.