cart-lambda

AWS Lambda Cart Micro Service - Serverless REST API's

TODO LIST

adding aws cognito security aspect

add more unit testing mocking dynamoDB locally

##Architecture

Presentation

http://www.slideshare.net/dhanugupta/aws-lambda-cart-microservice-server-less

Various components used in this example:

AWS API Gateway

API Gateway helps developers deliver robust, secure, and scalable mobile and web application back ends.

AWS Lambda Functions

Run code without thinking about servers. Pay for only the compute time you consume.

AWS DynamoDB

Amazon DynamoDB is a fast and flexible NoSQL database service for all applications that need consistent, single-digit millisecond latency at any scale. It is a fully managed cloud database and supports both document and key-value store models.

Deployment

JAVA, Gradle, Jenkins Deployment

AWS DynamoDB

Create Table on DynamoDB

Name : ‘cart’

Partition Key : ‘loginId’ (String)

Sort key : ‘sku’ (String)

Read Capacity Units : 100

Write Capacity Units : 50

Note: If you want to read more on provisioned read/write capacities

http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/ProvisionedThroughputIntro.html

AWS Lambda

Create a new Lambda function. As

Name : CartRequestRouter

Handler : com.org.cart.router.RequestRouter::lambdaHandler

Runtime Env : Java

Memory : 1024

Timeout : 30secs to start with

Note :
1. Ensure your Lambda function is using the correct IAM role. The role must have the ability to write/read to DynamoDB.
2. All Lambda interactions are logged in Cloudwatch logs. View the logs for debugging.
The Lambda function handler tells Lambda what java method under com.org.cart.router.RequestRouter - lambdaHandler(InputStream request, OutputStream response, Context context)
Review & create function.

###API Gateway

Create a new API. Give it a name and description. This will be our RESTful endpoint.
Create a resource. The path should be /cart , for example.
We need to add one more resource as /read under cart as /cart/read. Create a GET method with Lambda integration.
Now let's setup the Integration Request. Cart Micro Service GET request will be of type application/json. This Integration step will map this type to a JSON object, which Lambda requires. In the Integration Requests page create a mapping template. Content-type is application/json and template:

{
  "body" : $input.json('$'),
  "headers": {
    #foreach($header in $input.params().header.keySet())
    "$header": "$util.escapeJavaScript($input.params().header.get($header))" #if($foreach.hasNext),#end
    
    #end
  },
  "params": {
    #foreach($param in $input.params().path.keySet())
    "$param": "$util.escapeJavaScript($util.urlDecode($input.params().path.get($param)))" #if($foreach.hasNext),#end
    
    #endhjkyt
  },
  "query": {
    #foreach($queryParam in $input.params().querystring.keySet())
    "$queryParam": "$util.escapeJavaScript($util.urlDecode($input.params().querystring.get($queryParam)))" #if($foreach.hasNext),#end
    #end
  },
  "stage" : "$context.stage",
"requestId" : "$context.requestId",
"apiId" : "$context.apiId",
"resource-path" : "$context.resourcePath",
"resourceId" : "$context.resourceId",
"httpMethod" : "$context.httpMethod",
"sourceIp" : "$context.identity.sourceIp",
"userAgent" : "$context.identity.userAgent",
"accountId" : "$context.identity.accountId",
"apiKey" : "$context.identity.apiKey",
"caller" : "$context.identity.caller",
"user" : "$context.identity.user",
"userArn" : "$context.identity.userArn"
}

More on Intergration Requests. $input.params() parse the request object for the corresponding variable and allows the mapping template to build a JSON object.

![Screencast](https://github.com/dhanugupta/cart-aws-lambda/blob/master/aws-api-gateway-cart-REST.png?raw=true)

Let's ensure the response is correct. Cart Micro Service will respond as valid JSON.
Lambda cannot return valid JSON Response.
Now let's deploy this API, so we can test it! Click the Deploy API button.

###Connecting the dots & Testing

We should now have a publically accessible GET endpoint. Ex: https://xxxx.execute-api.us-west-2.amazonaws.com/prod/cart
Make sure you add API Key to API Gateway for security purpose. Each client has to provie x-api-key:xxxxxxxx to access each REST API's.
You can access read API as https://xxxx.execute-api.us-west-2.amazonaws.com/prod/cart/read?loginId=xxxx and response will be JSON Object like

{ cart:[],
  code:200,
  loginId:xxx}

##Troubleshooting

Cloudwatch logs are your friends.