Nans' blogs

Lambda training

March 11, 2020

Learn AWS Lambda and see real world example with serverless

main documentation : https://serverless.com/

What is lambda

functions limited by time run on demand scaling is automated -> that’s why we call it “Serverless”

Pricing

  • pay per request
  • pay per compute time

AWS Lambda integrations

  • API Gateway -> to build a REST API
  • Kinesis -> processing data in streams
  • DynamoDB -> Managed NoSQL database

Example : Thumbnail creation

“Database Trigger-like” behavior for S3 New image in S3 -> trigger -> AWS Lambda function creates a thumbnail and push it to S3

/!\ the handler is the name of function that will be called in lambda The instructor only did a “hello world”.

The Serverless Framework

Aims to ease the pain of creating, deploying, managing and debugging lambda functions. Integrates with CI/CD tools. CloudFormation support (templates for deploying).

npm install -g serverless

IAM => Create a serverless-admin (new user). Programmatic access, and give administrator access. (not best practice though …)

serverless config credentials --provider aws --key XXX --secret YYY --profile serverless-admin

Hello world using the Serverless framework

serverless or sls => list of commands.

sls create --template aws-python --path hello-world-python

serverless.yml add

profile: serverless-admin
region: eu-west-3
sls deploy -v

the code is uploaded to s3, and then CloudFront is configured. IAM role is created for us.

Running a function from the command line

sls invoke -f hello -l

 Updating the function

change the print statement.

sls deploy function -f hello

=> how to integrate that with a proper CI/CD system ?

Fetching function logs

sls logs -f hello -t

enables to stream function logs as they happen !

 Remove the function

sls remove

add an IAM role statement to a function

iamRoleStatements:
  - Effect: "Allow"
    Action:
    - "lambda"
    Resource:
    - "*"

VPC for lambda functions

can launch a lambda in a VPC so that they can access EC2 instances or RDS instances. 2020 03 12 11 14 30 can specify securityGroupIds and subnetsId in the serverless.yml file.

Real world example : Service to create S3 image thumbnails

image thumbnail workflow

  • S3 events
  • plugins to deploy python dependencies (docker needed)

Triggering a function from an s3 event : 2020 03 12 11 27 59

plugin : serverless-python-requirements it installs what’s written in requirements.txt file. Pillow => import PIL

Real world example : REST API with API Gateway and DynamoDB

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Lambda functions are stateless, they don’t keep anything in memory, so they will write to DynamoDB.

package.json => like requirements.txt

environment :
  DYNAMODB_TABLE: ${self:service}-${opt:stage, self:provider.stage}

2020 03 12 13 56 44

2020 03 12 13 58 10

POST on /todos => call create function this is wired to the API gateway

under resources, you can specify the cloud formation template

2020 03 12 14 04 26

2020 03 12 14 05 12

response should always have a statusCode and a body.

2020 03 12 14 06 51

 Personal investigation : creating a full stack app

If you want to build an app that can leverage that rest API that is written in Lambda, you can use aws-amplify : https://aws-amplify.github.io/docs/js/api.


Written by Nans Dumortier who is a French Software Developer.
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