AWS Lambda function url call gives 502 Bad gateway - amazon-web-services

Question

I'm getting started with AWS lambda and created a basic java handler like below.
import com.amazonaws.services.lambda.runtime.Context;
import com.amazonaws.services.lambda.runtime.RequestHandler;
import com.amazonaws.services.lambda.runtime.LambdaLogger;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import java.util.Map;
// Handler value: example.Handler
public class Handler implements RequestHandler<Map<String,String>, String>{
Gson gson = new GsonBuilder().setPrettyPrinting().create();
#Override
public String handleRequest(Map<String,String> event, Context context)
{
LambdaLogger logger = context.getLogger();
String response = "200 OK";
// log execution details
logger.log("ENVIRONMENT VARIABLES: " + gson.toJson(System.getenv()));
logger.log("CONTEXT: " + gson.toJson(context));
// process event
logger.log("EVENT: " + gson.toJson(event));
logger.log("EVENT TYPE: " + event.getClass());
return response;
}
}
When I'm testing the lambda function via AWS portal, it is working fine. But when I'm triggering the same using function URL like below, I'm getting a 502: Bad Gateway error.
curl --location --request POST 'https://xyz.lambda-url.region.on.aws?message=HelloWorld' \
--header 'Content-Type: application/json' \
--data-raw '{
"some-key": "some-value"
}'
An error occurred during JSON parsing: java.lang.RuntimeException
java.lang.RuntimeException: An error occurred during JSON parsing
Caused by: java.io.UncheckedIOException: com.amazonaws.lambda.thirdparty.com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of java.lang.String out of START_OBJECT token
at [Source: (ByteArrayInputStream); line: 1, column: 84] (through reference chain: java.util.LinkedHashMap["headers"])
at com.amazonaws.services.lambda.runtime.serialization.factories.JacksonFactory$InternalSerializer.fromJson(JacksonFactory.java:184)
Caused by: com.amazonaws.lambda.thirdparty.com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of java.lang.String out of START_OBJECT token
at [Source: (ByteArrayInputStream); line: 1, column: 84] (through reference chain: java.util.LinkedHashMap["headers"])
I've mentioned the Auth type of Function URL to NONE as well. Is there anything I'm missing here? Thanks in advance.

Answer 1

According to aws docs, even though you specify AuthType as NONE, your function's resource-based policy is always in effect and must grant public access before your function URL can receive requests.
You can re-verify your lambda role policy if it has public access and also with AuthType set to NONE.