dynamo-replicator

DynamoDB Replicator

Lambda-ready npm package for replicating DynamoDB tables within or between regions.

Supports one-way replication (single master to slave(s))

Usage

Prerequisites

You'll need NodeJS and NPM installed on your local machine.

Prepare your DynamoDB table

Add a stream to the DynamoDB table you want to use as your master.

• In the Overview tab of the DynamoDB table in the AWS console click Manage Stream.
• In the overlay that pops up choose New Image (although New and old images should also work should you need that for other reasons).
• Click Enable.

Alternatively, if you want to provision your DynamoDB table with CloudFormation add the StreamSpecification property to the AWS::DynamoDB::Table object, e.g.

{
  "AWSTemplateFormatVersion": "2010-09-09",
  "Resources": {
    "myTable": {
      "TableName": "mytable",
      "StreamSpecification": {
        "StreamViewType": "NEW_IMAGE"
      }
    }
  }
}

Create the replication Lambda function

• Create a new empty directory on your computer
• Within that folder create two files, one called package.json and another called index.js.
• Edit package.json and save {} as the contents of that file.
• In your terminal type npm install --save dynamo-replicator es6-promise
• Edit index.js and save the contents of the file shown below (changing SLAVE-REGION and SLAVE-TABLE to be the region and table name of the DynamoDB to be replicated to).
• zip the contents of the folder up.
• Create a new Lambda function with a role that has sufficient IAM permissions (as a minimum it needs dynamodb::PutItem and dynamodb::DeleteItem on the slave table.
• On the Triggers tab of your master DynamoDB, click Create Trigger and New Function; for the Configure event source options, ensure the DynamoDB table is your master table and leave everything else as default and click Next; for the Configure function options name your function something like dynamodb-replicator and for Code entry type select Upload a .ZIP file and choose the zip file created earlier.
• Repeat the previous step for multiple slaves changing SLAVE-REGION and SLAVE-TABLE in index.js each time and re-zipping for each slave.
• Test by creating and deleting items from the master table and ensuring that the slaves update accordingly.

Contents of index.json:

'use strict';

require('es6-promise').polyfill();

var replicator = require('dynamo-replicator')({
	region: 'SLAVE-REGION',
	table: 'SLAVE-TABLE'
});

exports.handler = function(event, context) {
	replicator.process(event)
		.then(function() {
			context.succeed('success');
		})
		.catch(function(err) {
			context.fail(err);
		});
};