Serverless AWS Ruby SQS with DynamoDB example

This is an example of the usage of the SQS with DynamoDB, API Gateway, and AWS Lambda functions, and Cloudwatch for monitoring. The service is for the purpose of creating lottery coupons for people. Each and every coupon consists of the id, first_name, last_name and coupon_value as well as of created_at timestamp. API Gateway is triggering producing an SQS message, and then the consumer will create a record within the DynamoDB table. The incoming requests are validated with the usage of dry-schema.

For the purpose of SQS part, the Lift construct was used, to allow using AWS CDK constructs functionalities.

Diagram

Regarding Lift queue construct:

• It creates an SQS queue with a worker running on AWS Lambda.
• A worker Lambda function, the purpose here is to process each and every message which is in the queue.
• An SQS DLQ the purpose here is to store all failed messages.
• Cloudwatch for alerting via email. Applies when SQS DLQ has failed messages, and the alerting option is enabled (in our case is true).

Setup

npm install to install all needed packages.

Deployment

In order to deploy the service run:

sls deploy

for deploying with a specific profile (located in ~/.aws/credentials) you can simply use the command:

AWS_PROFILE=YOUR_PROFILE_NAME sls deploy

for deploying to the specific stage, let's say staging do:

sls deploy --stage staging

The expected result should be similar to:

Serverless: Running "serverless" installed locally (in service node_modules)
Serverless: Packaging service...
Serverless: Excluding development dependencies...
Serverless: Clearing previous build ruby layer build
[ '2.1' ]
Serverless: Installing gem using local bundler
Serverless: Zipping the gemfiles to examples/aws-ruby-sqs-with-dynamodb/.serverless/ruby_layer/gemLayer.zip
Serverless: Configuring Layer and GEM_PATH to the functions
Serverless: Uploading CloudFormation file to S3...
Serverless: Uploading artifacts...
Serverless: Uploading service serverless-ruby-sqs-dynamodb.zip file to S3 (7.71 KB)...
Serverless: Uploading service gemLayer.zip file to S3 (1.35 MB)...
Serverless: Validating template...
Serverless: Updating Stack...
Serverless: Checking Stack update progress...
...........................
Serverless: Stack update finished...
Service Information
service: serverless-ruby-sqs-dynamodb
stage: dev
region: your-region-here
stack: serverless-ruby-sqs-dynamodb-dev
resources: 22
api keys:
  None
endpoints:
  POST - https://XXXXXXXXXX.execute-api.your-region-here.amazonaws.com/dev/lottery
functions:
  createLotteryCoupon: serverless-ruby-sqs-dynamodb-dev-createLotteryCoupon
  lotteryQueueWorker: serverless-ruby-sqs-dynamodb-dev-lotteryQueueWorker
layers:
  gem: arn:aws:lambda:your-region-here:XXXXXXXXXXXXXX:layer:serverless-ruby-sqs-dynamodb-dev-ruby-bundle:3
lotteryQueue:
  queueUrl: https://sqs.your-region-here.amazonaws.com/XXXXXXXXXXXX/serverless-ruby-sqs-dynamodb-dev-lotteryQueue

Usage

After the deployment, you will obtain the API Gateway endpoint. Simply send the POST request to it with params (either curl, or via Postman):

curl --request POST 'https://XXXXXXXXXX.execute-api.your-region-here.amazonaws.com/dev/lottery' --header 'Content-Type: application/json' --data-raw '{"first_name": "Daniel", "last_name": "Ani", "coupon_value": 99}'

The response to the above requests will be:

{
    "message": "Message sent"
}

To check created records check your DynamoDB table:

Important: The DynamoDB table name is a combination of service name and stage. For the dev stage it will be:

serverless-ruby-sqs-dynamodb-dev

For checking the CloudWatch logs:

• from lambda dashboard the createLotteryCoupon function:

• directly from CloudWatch logs createLotteryCoupon function:

Same for the lotteryQueueWorker function.

SQS

It is possible to configure email alerts in case messages end up in the dead letter queue. Within the queue construct edit the alarm value to your email.

Make sure, that you confirm the subscription to the AWS Notification through your email:

For more options, it's possible to set up more settings.

Log retention

The log retention is setup for 30 days. To change it simply change the value of this attribute in serverless.yml file:

logRetentionInDays: 30

Structure

Path	Explanation
./src	All code for the project.
./src/handlers/handler	Lambda function for producing sqs messages.
./src/handlers/worker	Lambda function for consuming sqs messages.
./src/common/	Space for common, reusable pieces of code.
./src/common/adapters/dynamo_db_adapter.rb	Adapter for communication with DynamoDB with the usage of AWS SDK for Ruby. Only used for creating new records.
./src/common/adapters/sqs_adapter.rb	Adapter for communication with SQS with the usage of AWS SDK for Ruby. Only used for sending new messages to SQS.
./src/common/services/create_lottery_coupon_service.rb	The service object pattern is widely used within ruby/rails developers. A class that is responsible for doing only one thing. In our case is creating a lottery coupon record to the DynamoDB.
./src/common/services/create_sqs_message_service.rb	In our case is sending a message to SQS.
./src/common/helpers/requests_helper.rb	Helper methods for requests. In our case, for parsing and symbolize hash keys.
./src/common/schemas/lottery_coupon_schema.rb	Schemas for entities within the application. In our case, the schema with required keys and data types for lottery coupon.
./src/common/serializers/error_serializer.rb	Error serializer for 422 error. It gathers the dry-schema validation errors and puts them in a proper structure.
./src/common/validators/lottery_coupon_validator.rb	Validator for the lottery coupon record. It's validating the incoming request against the dry-schema structure and returns errors and information on whether the params are incorrect.

Serverless plugins

For this example, there are two serverless plugins used:

Plugin	Explanation
serverless-ruby-layer	For bundling ruby gems from Gemfile and deploys them to the lambda layer.
serverless-lift	For using AWS CDK construct within the Serverless Framework. In this example, queue construct.

Ruby gems

Gem	Explanation
aws-sdk-dynamodb	It's a part of the AWS SDK for Ruby. Used for DynamoDB, in the case of this example - the creation of the new record.
aws-sdk-sqs	It's a part of the AWS SDK for Ruby. Used for SQS, in the case of this example - produces and handles messages from the queue.
dry-schema	For the purpose of the validation of the incoming requests. Validate both schema and data types.

Eject from the Lift plugin

A very cool aspect is the eject|. In case your project grows beyond the plugin, you can eject from Lift at any time, as the plugin is based on CloudFormation. You're not chained to Lift at all.

Remove service

To remove the service do:

sls remove

And the stack will be removed from the AWS.