lambda-s3-microservice

Example Lambda microservice for filtering and returning S3 CSV data. Designed to be used with an API Gateway.

Make a read only serverless REST endpoint out of a file residing in S3. Useful for very slow changing data that a disperate system needs occasionally. This is a demo verion of real Lambda I creaed at work to return valid 10 digit vins for any make, we use it to validate a VIN against target makes during ingest.

Returns unique values only.

Install

$>npm install

Lambda Usage

You may use this Lambda as is but it is desined to play nice with an API Gateway configured as a REST API in front of it. It expects an event object with one param search on it. It will return a filtered view of an S3 csv file for the search param. The column to compare it to is set in config.js

Lambda Event Example:

Lets pretend we had a dataset like so sitting in S3
make,model,trim,year,price
BMW,3 series,325,2015,42195
BMW,5 series,525,2015,62195
Ford,F150,Lariet,2016,23560
Ford,F150,Lariet,2016,23560
...and so on

event
{
  "search": "BMW"
}

response
[ "3 series",
  "5 series", ...
]

Lambda Exceptions and Errors

The Lambda function will return errors with the following format, designed to be regex-able by AWS API Gateway to turn into a matching HttpStatus and formated response object. For example a search with no data will return a "Not Found" so that the API Gateway can map this to HttpStatus and HttpStatusCode NOT FOUND - 404.

{  "errorMessage": "<Http Status Text> : <Lambda error message>" }
eg.
{  "errorMessage": "Not Found : chicken" }

Response mapping

Using integration response methods you can map error messages and responses from the lambda to appropriate HttpStatus codes and messages.

Example (error response):

//response from lambda  
{  "errorMessage": "Not Found : no data found for search chicken" }

//regex rule in API Gateway response integration mapping  
Not Found.*

//mapper in API Gateway
{ "status" : "NOT FOUND", "errorMessage": "$input.path('errorMessage')", "statusCode":404 }

//response from API Gateway  
application/json  
404
{ "status" : "NOT FOUND",
  "errorMessage": "Not Found : no data found for search chicken",
  "statusCode":404
}  

Deployment

The deploy directory contains shell scripts to create and upload a Lambda function as well as set policy on it. AWS cli installation and properly configured aws credentials on a must for this shell to work.

No CLI exists for API gateway at this time.

You can experiement with it locally by calling $>node index.js test

Reference

AWS Lambda Documentation
AWS API Gateway