How do I use batchWriteItem with Node.js to query AWS DynamoDB?

Question

I'm new to AWS and I'm having problems trying to develop a simple Lambda function with Node.js. In DynamoDB, I have a table named Game with 3 attributes: gamepk, user, result. In just one single execution of the Lambda function, I want to insert a collection of game elements (the number of elements in the collection could vary). I had been reading some tutorials and it said I should use batchWriteItem, but because the collection of Game elements is variable I don't know how to proceed.

Could somebody write a function in Node.js that solves my problem?

An example of the JSON that the lambda function receives is this one:

    {
        "games": [{
                "gamepk": "1",
                "user": "rolo",
                "result": "1-0"

            },
            {
                "gamepk": "2",
                "user": "jhon",
                "result": "1-1"
            }
        ]
    }

Chad Elias · Accepted Answer · 2018-08-16 01:23:38Z

35

This should get you what you need.

Create a New Lambda Function
Select Node Version 6
Select a Role or Create a New one that has DynamoDB Access to Write!
Open Created Function in the Web Console

Paste the Snippet Bellow into the Cloud 9 Editor

const AWS = require('aws-sdk/global');

exports.handler = (event, context, callback) => {
// The event parameter is the input to your lambda function
console.log(JSON.stringify(event));
let lambdaInput = event['PROPERTY_NAME_DEFINED_IN_POST'];
let games = [];
let documentClient = new AWS.DynamoDB.DocumentClient();

lambda.forEach(item => {
  games.push({
    PutRequest: {
      Item: {
        gamepk: item['gamepk'],
        user: item['user'],
        result: item['result']
      }
    }
  });
});

let params = {
    RequestItems: {
        'TABLE_NAME': games
    }
};

documentClient.batchWrite(params, function(err, data) {
    if (err) {
        callback(err);
    } else {
        callback(null, data);
    }
});
}

Save the Function and then you are going to want to select the drop down at the top that says 'Select a Test Event' and then select 'Configure Test Events'.

This will open a new dialog, just save the JSON that is in the main text area and give the test a Name and Save it.

Now select that test that you just made from the 'Select a Test Event' drop down and then click 'Test' in the top right.

This documentation could be found at AWS Javascript SDK

edited Aug 16, 2018 at 1:23

answered Aug 15, 2018 at 4:26

Chad Elias

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2 Comments

rolo Over a year ago

Thank you so much for your answer, it worked!. But theres a thing that im not urdestanding, and maybe I dont explained very well in my question (my english is not good). The lambda function is "activated" by an api-gateway, when someone want to insert something in table "Game" it sends a POST with the collection in a JSON. Seeing your answers, its like your function only inserts two elements. Could you say me how to modify the function to recieve a collection in JSON and insert all of the elements at the same time?.

Chad Elias Over a year ago

I've updated the lambda function to suit your needs, please mark correct if this works for you.

JxDarkAngel · Accepted Answer · 2019-07-04 15:05:16Z

7

As an additional help for the answer , you can use an environment variable and use it in the following way:

const MI_TABLE = process.env.MI_TABLE

  let params = {
      RequestItems: {
           [ MI_TABLE ] : games
      }
  };

return await batchWrite(params);

answered Jul 4, 2019 at 15:05

JxDarkAngel

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