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Serverless DynamoDB Stream Example

This is a bare-bones Serverless project that simply shows how to:

  1. Give your Lamdbas DynamoDB IAM roles so they can process DynamoDB Streams
  2. Use Serverless's resources deploy to instruct CloudFormation to create a DynamoDB Table with a Stream (of StreamViewType NEW_AND_OLD_IMAGES) in your stages
  3. Capture the ARN of the Stream attached to the DynamoDB Tables created in Step 2 into your project variables per stage
  4. Set your Lamdba's trigger event to be the DynamoDB stream events for the table created in the stage you deploy to

Getting Started

1. Install Serverless

npm install -g serverless

2. Setup your AWS Credentials

Follow the official guide here.

3. (optional) Customize Your Resources/Set up your Stage

This is just a sample to show how to link up the moving pieces. You'll probably want to edit the name of your DynamoDB table, possibly the type of DynamoDB Stream you want associated with the table, the provisioned throughput of the tables, and the name of the output variable for your project inside s-resources-cf.json. You can create many DynamoDB tables following the same pattern in the same s-resources-cf.json, just add more entries.

You're also obviously going to have your own function you want to run in response to a DynamoDB event. The sample function processStreamEvent simply logs the event it receives to the console so you can see it in CloudWatch. The only important part about the sample function is the event configuration in processStreamEvent/s-function.json.

4. Deploy Resources

sls resources deploy

5. Deploy Function & Event

sls dash deploy then deploy everything to the stage you want.

Testing

Log into the AWS Console (website), navigate to your DynamoDB table and insert an item in the table you created. Go to CloudWatch and in a few moments (possibly a couple minutes if your Lambda hasn't been run in the last 10 minutes and is cold), you should see the event output in your Logs.

You'll find the info you want under the event.dynamodb object.

Learning

If you're trying to figure out what all the different pieces that have been added compared to a freshly generated Serverless project, simply follow the git commit history, it explains what's happening step by step.

Notes

If you're in your AWS Console, looking at your Lambda function, keep in mind that you will only see the DynamoDB event source configured when you click on the tagged version of your function that has the same name as the stage you deployed into. (For example, you need to click on the blue tag named dev if you created a stage called dev.) And, it's State should be set to Enabled.

Questions / Issues?

Open an issue on this repo or hit up @ianserlin on the serverless/serverless gitter.

This code sample is provided by Useful IO, because we ❤️ Serverless.

We're a distributed software development team and build world-class apps for web and mobile using Meteor and Serverless.

If you'd like to build something useful using Serverless just shoot an email [email protected].