Triggering a lambda using SNS notification not working

Question

package example;
import java.io.*;
import com.amazonaws.services.lambda.runtime.Context; 
public class LambdaMethodHandler {
    public String handlerString(String input,Context context) {
    System.out.println(input.length());
        return input;
    }
}
// This is my function policy
{
    "Version": "2012-10-17",
    "Id": "default",
    "Statement": [
        {
            "Sid": "sns-xxxx-Sns_Lambda_test",
            "Effect": "Allow",
            "Principal": {
                "Service": "sns.amazonaws.com"
            },
            "Action": "lambda:invokeFunction",
            "Resource": "arn:aws:lambda:xxxxx:function:theSimplestLambda",
            "Condition": {
                "ArnLike": {
                    "AWS:SourceArn": "arn:aws:sns:eu-west-1:xxxx:Sns_Lambda_test"
                }
            }
        }
    ]
}

Handler : I am very new to amazon web services, I made a demo lambda. When i invoke it using the cli(Or web console) with any random string, it works and shows the length of the input string on the webpage of lambda. Then i subscribed it to a SNS topic and tried to publish a event with a random string to it. I can't see the result on the webpage(lambda) i.e length of the string is not displayed. How to know that the lambda is processing the string correctly?

If you created the resources using CloudFormation (or CLI), you need to give Lambda permission to get invoked: aws lambda add-permission --region REGION_NAME --function-name LAMBDA_FUNCTION_NAME --statement-id SOME_ID --action lambda:InvokeFunction --principal config.amazonaws.com. — krishna_mee2004, Jul 31 '17 at 15:49
I checked my function policy and Effect is allowed, could you see it and tell me that if i am missing something.@KrishnaKumarR — Crosk Cool, Jul 31 '17 at 15:57
This is in SNS. That is correct. But, you need to enable Lambda to get invoked. The command to do that was mentioned in the previous comment. — krishna_mee2004, Jul 31 '17 at 16:49
Possible duplicate of [AWS Lambda & SNS: Invoke Lambda cross-region](https://stackoverflow.com/questions/35006556/aws-lambda-sns-invoke-lambda-cross-region) — adamkonrad, Jul 31 '17 at 20:40
Your question is seeking a solution similar to https://stackoverflow.com/questions/35006556/aws-lambda-sns-invoke-lambda-cross-region/35017361#35017361 — adamkonrad, Jul 31 '17 at 20:40

score 0 · Accepted Answer · answered Aug 01 '17 at 17:07

Apparently, the aws lambda was correctly getting invoked, the reason why the length of the string that I displayed in the handler wasn't getting displayed because of the parameter that i was taking inside the lambda, In order to process something as input from SNS i have to take a event of type SNSevent in the argument and then process it afterwards.

Triggering a lambda using SNS notification not working

1 Answers1