将变量从调用的 Lambda Function 传递到 DynamoDB

Question

I'm trying to invoke a string from another lambda function. This string should be written into an array which is then uploaded to a DynamoDB Table along with information such as the date.

Yet when I try to get the variable called "key" in the lower part of the script where it is supposed to upload to DynamoDB, it is undefined and not written into the table.

I tried using the window.variable command but somehow AWS lambda didn't recognize it. All in all I'm quite new and a bit confused on how to pass variables between different functions within in a JavaScript.

Maybe someone can help me. Thank you!

 var key; //define key as gloabal variable var AWS = require('aws-sdk'); //load aws-sdk AWS.config.region = 'eu-central-1'; //Set server region var lambda = new AWS.Lambda(); var db = new AWS.DynamoDB.DocumentClient({region: 'eu-central-1'}); //region of dynamo server exports.handler = function(event, context) { var params = { FunctionName: 'string_Generator', // called Function InvocationType: 'RequestResponse', }; lambda.invoke(params, function(err, data) { if (err) { context.fail(err); } else { context.succeed(data.Payload); } key = data.Payload; //set the payload/string as "key" variable }); } exports.handler = async (event) => { var params = { Item: { date: Date.now(), Key: key }, TableName: 'Productkeys' }; params.Item.partitionkey = "3"; //putting in the partition key of the DynamoServer return await db.put(params).promise(); }

Answer 1

One problem is you are overwriting your handler function, because you have 2 functions with the same name. The other thing is it looks like this might be better in one function, as one depends on the other and I don't know how you are calling them or from where.

Try this:

exports.handler = async () => {
    var params = {
        FunctionName: 'string_Generator', // called Function
        InvocationType: 'RequestResponse',
    };
    
    lambda.invoke(params, function(err, data) {
        if (err) {
            context.fail(err);
        } else {
            context.succeed(data.Payload);  
        }

        var params2 = {
            Item: {
                date: Date.now(),
                Key: data.Payload
            },
            TableName: 'Productkeys'
        };
        params2.Item.partitionkey = "3";
        return await db.put(params2).promise();
    });
};

Answer 2

Okay I went through it the whole night but I was able to fix it with @ffritz advice.

I tried some different combinations and tried to understand the syntax a lot better until it finally worked out. It might not be the prettiest code but it works .

Thank you for your help guys.

Edit: I found one more issue. The code doesnt get executed immediately. The generated keys just stay in the function and are deployed upon the next call. So when I'm calling the function via API Gateway, I dont deploy the freshly generated string, but the old one. I still need to find a fix for that.

Edit 2: Now it works. I updated the script below.

 var AWS = require('aws-sdk'); //load aws sdk AWS.config.region = 'eu-central-1'; //Server of Lambda var lambda = new AWS.Lambda(); var db = new AWS.DynamoDB.DocumentClient({region: 'eu-central-1'}); //region of DB Server exports.handler = function(event, context, callback) { var params = { //set parameters for the call FunctionName: 'String_Generator', // called Function InvocationType: 'RequestResponse', }; lambda.invoke(params, function(err, data) { //Invoke other function if (err) { context.fail(err); } else { //if invoke gets string var params2 = { //set parameters for DB put Item: { date: Date.now(), Key: data.Payload //set the string as "Key" variable }, TableName: 'Productkeys' }; params2.Item.partitionkey = data.Payload; //add the partition key db.put(params2); //put the params2 into the DB callback(null, data.Payload); } }); };