Lambda function specified as a Destination is not being triggered

Question

I have a lambda function that verifies user credentials. Upon success it should call another lambda function, as a destination, that generates a token. When I test the first function, it is successful but it does not call the destination which is the other lambda function. It only gives me the success message from the first function.

Function one

exports.handler = function (event, context) {

    var id = event.email;
    var params = {
      TableName: "User",
      KeyConditionExpression: "#email = :email",
      ExpressionAttributeNames:{
        "#email": "email",
        },
      ExpressionAttributeValues: {
          ":email": {S: event.email},
      }

    };

    if (id && id !== '') {

        dynamo.query(params, function (err, data, callback) {
            if (err) {
                context.done(err);
            }
            else {
                var user = data.Items[0];
                if (user) {
                    var encryptedParams = {
                        CiphertextBlob: Buffer.from(user.password.B),
                    };
                    kms.decrypt(encryptedParams, function (err, decrypteddata) {
                        if (err) {
                            console.log(err, err.stack);
                            context.done(err);
                        }
                        else {
                            if(event.password == decrypteddata.Plaintext.toString()) {
                                console.log("User authenticated");
                            }
                        }
                    });
                }
            }
        });
    }
    else {
        return {
            statusCode: 400,
            body: "No email provided."
        }           
    }

};

Function two

exports.handler = async (event) => {

    var expires = moment().add('days', 7).valueOf();

    var token = jwt.encode({
      iss: event.email,
      exp: expires
    }, app.get('jwtTokenSecret'));

    const response = {
        token: token,
        express: expires,
        statusCode: 200
    };

    console.log("token granted");

    return response;
};

I don't see any code in the first function which would call the second? Also you should chain lambdas using SNS or Step functions. Calling them directly is not a very good practice when developing distributed system. — Marcin
– Marcin, Commented Mar 21, 2020 at 23:11
I think the OP is using AWS Lambda Destinations | AWS Compute Blog, which is rather new. — John Rotenstein
– John Rotenstein, Commented Mar 22, 2020 at 0:44
@Skip The above link mentions "Ensure that your Lambda function execution role includes access to the destination resource". What is in the IAM Role associated with the first Lambda function? — John Rotenstein
– John Rotenstein, Commented Mar 22, 2020 at 0:46
@JohnRotenstein Yes the lambda role attached to the first function has full access to lambda functions. I ran into the issue prior. — Skip Bassey
– Skip Bassey, Commented Mar 22, 2020 at 1:34

John Rotenstein · Accepted Answer · 2020-03-22 04:40:42Z

1

Your code doesn't seem to be indicating when a successful execution has been completed. Destinations needs the "OnSuccess" indicator to determine which destination to trigger. This is possibly why the second function is not being executed.

See: Lambda Destinations: What We Learned the Hard Way - CloudProse - Trek10 Blog

answered Mar 22, 2020 at 4:40

John Rotenstein

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