DynamoDB streams lambda trigger

batch-write.js

const items = [{
  "Username":   "First",
  "Timestamp":  "2017-08-07T19:51:00.794Z",
  "Message":    "first item in batch"
},
{
  "Username":   "Second",
  "Timestamp":  "2017-08-07T19:51:00.794Z",
  "Message":    "second item in batch"
},
{
  "Username":   "Third",
  "Timestamp":  "2017-08-07T19:51:00.794Z",
  "Message":    "third item in batch"
}];

const putRequests = items.map((item) => {
  return {
    PutRequest: {
      Item: item
    }
  };
});

const params = {
  RequestItems: {
    BarkTable: putRequests
  }
};

const aws = require('aws-sdk');
const REGION = 'us-east-1';

const db = new aws.DynamoDB.DocumentClient({ region: REGION });
db.batchWrite(params).promise().then(() => {
  console.log('success');
}).catch((e) => console.error(e));

index.js

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

const TABLE_NAME = 'BarkTable';
const REGION = 'us-east-1';

exports.handler = (event, context, callback) => {
  const DynamoDB = new AWS.DynamoDB.DocumentClient({region: REGION})

  const records = event.Records;
  console.log('Processing ' + records.length + ' records');
  
  const jsonRep = JSON.stringify(records, null, 2);
  console.log('Events: ' + jsonRep);
  
  const lastRecord = records.pop();
  
  const inserts = records.map((record) => {
    if (typeof record.dynamodb.NewImage === 'undefined') {
      return Promise.resolve();
    }

    const Username = record.dynamodb.NewImage.Username.S;
    const Timestamp = record.dynamodb.NewImage.Timestamp.S;
    const Message = record.dynamodb.NewImage.Message.S;
    const Item = { Username, Timestamp, Message, Processed: "true" };
    const params = {
      TableName: TABLE_NAME,
      Item
    }
    return DynamoDB.put(params).promise();
  });

  Promise.all(inserts).then(() => {
    callback('Failed to process last record: ' + JSON.stringify(lastRecord, null, 2));
  }).catch(err => {
    callback(err);
  });
};

test-event.json

{
  "Records": [
    {
      "eventName": "INSERT",
      "dynamodb": {
        "NewImage": {
          "Message": {
            "S": "Testing...1...2...3"
          },
          "Timestamp": {
            "S": "2016-11-18:14:32:17"
          },
          "Username": {
            "S": "Jane Doe"
          }
        }
      }
    },
    {
      "eventName": "INSERT",
      "dynamodb": {
        "NewImage": {
          "Message": {
            "S": "Testing...3...2...1"
          },
          "Timestamp": {
            "S": "2016-11-18:14:32:17"
          },
          "Username": {
            "S": "John Smith"
          }
        }
      }
    }
  ]
}