Node.js is not outputting as expected

Question

I struggle to get my node.js code to function as I want. It is used for an AWS Lambda function.

The code Scan and Output a whole table in a DynamoDB. The issue is I almost never get the console.log("DB SCANNED!") in readdb function outputted in the console ( and no values loaded to "items").

var AWS = require('aws-sdk');
AWS.config.update({region: 'eu-west-1'});
var ddb = new AWS.DynamoDB({apiVersion: '2012-10-08'});

var table = "TABLE";

var paramsRead = {
    TableName: table,
  };


exports.handler = async (event) => {

await readdb();
console.log("END");

};


function readdb(){
  ddb.scan(paramsRead, function(err, data) {
    if (err) {
      console.log("Error reading DynamoDB", err);
    } else {
      console.log("DB SCANNED!");
      var items = JSON.stringify(data.Items);
         let response = {
            statusCode: 200,
            body: items,
          };
    }
  }
  );
}

James · Accepted Answer · 2018-11-25 17:23:49Z

3

The Lambda is finishing too quickly because you aren't actually returning anything from readdb to await.

You need to return a Promise

function readdb() {
  return new Promise((resolve, reject) => {
    ddb.scan(paramsRead, (err, data) => {
      if (err) {
        console.log("Error reading DynamoDB", err);
        reject(err);
      } else {
        console.log("DB SCANNED!");
        var items = JSON.stringify(data.Items);
        resolve({
          status code: 200,
          body: items
        });
      }
    })
  });
}

...
const response = await readdb();

answered Nov 25, 2018 at 17:23

James

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1 Comment

aurelius Over a year ago

Can't thank you enough for that! It worked like a charm.

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