This document discusses using the Serverless Application Model (SAM) to develop serverless applications locally. It describes how SAM templates allow defining Lambda functions and APIs that can then be run locally using the SAM CLI. This avoids needing an internet connection to test functions and allows using local tools like debuggers. Examples are provided for local development workflows involving APIs, Lambda functions, DynamoDB, and S3 event processing. Key links are also provided to learn more about SAM templates, the SAM CLI, and running DynamoDB locally.

1. OFF THE CLOUD WITH
SERVERLESS APPLICATION
MODEL (SAM)
AWS MEETUP – FLASH PRESENTATION
ALEX
SPICYKEY LLC
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2. OFF THE CLOUD
• Problem: We love lambdas in the cloud to a failing.
• Symptoms:
• Our favorite debugging tools are on our laptops
• Local integration testing is easier than on the cloud
• We have to meet a sprint deadline and are coding on our laptops during a long cross country flight without
internet access to meet that deadline
• You are on a NASA space station and are preparing for your AWS Certification Exam without internet access
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3. EXAMPLE: A
SERVERLESS
APPLICATION
MODEL TEMPLATE
1 LAMBDA
1 API
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4. START-API …. HTTP://LOCALHOST:3000
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5. HOW DO I RUN A LAMBDA FUNCTION LOCALLY?
• Install aws-sam-local
• Create a Serverless Application Model (SAM) template file in YAML or JSON
• In your favorite shell, execute ‘sam local invoke’
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6. WHY IS THIS HARD
• Software Prerequisites
• Go
• Docker
• AWS command line tools
• AWS SAM local tools
• A debugger that can easily connect to a remote process by port
• IAM Prerequisites
• A profile with IAM rights on your laptop
• Configuration
• Docker networks
• Capturing lambda logs locally
• Must learn template language and write templates by hand
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7. LOCAL DYNAMODB + LOCAL LAMBDA
• Run DynamoDB on your laptop, http://localhost:8000
• Use Docker 18.3+ on a Mac OS X or Windows laptop for easy Docker Network routing to the host
(http://host.docker.internal:8000)
• Route the lambda function’s dynamodb client to your laptop’s DynamoDB endpoint (javascript/nodejs
example)
• const dynamodb = new AWS.DynamoDB({endpoint: 'http://host.docker.internal:8000'});
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8. SCENARIO – WEBSITE DEVELOPMENT
• Example: A react developer creates a progressive website that accesses APIs via fetch(). The developer
starts the web application locally. Two commands: ‘npm start’ and ‘sam local start-api’. The website is
accessible at http://localhost:3000 and the APIs are accessible at http://localhost:3001. The AWS
Lambda function uses aws-serverless-express to route APIs to code within the lambda function. The
lambda function authorizes http://localhost:3000 with CORS.
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9. SCENARIO – LAMBDA DEVELOPMENT
• Example: A developer wants to enhance a lambda function by improving the code. The developer pulls
the source code for the lambda on to their laptop. Then, write a SAM template for the lambda
function. After that, the developer creates a JSON document with an example input event. The
developer invokes the lambda with ‘sam local invoke –e sample-event.json’
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10. SCENARIO – S3 EVENT DEVELOPMENT
• Example: A developer has a javascript based lambda function that responds to S3 events that is buggy.
The developer creates a project in visual studio for the lambda function. The developer then creates a
SAM template for the function. First, the developer runs visual studio and sets a breakpoint. Then,
invokes the function with ‘sam local invoke –d 5858.’
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11. THREE IMPORTANT LINKS
• Serverless Application Model (SAM) Templates - https://github.com/awslabs/serverless-application-
model
• SAM Local Command Line Interface (CLI) - https://github.com/awslabs/aws-sam-local
• Local DynamoDB -
https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/DynamoDBLocal.html
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12. THANK YOU – ABOUT ME
• #Serverless
• #Alexa
• #Code
@spicykey
SpicyKey LLC develops apps for clients
https://spicykey.com https://youtube.com/spicykey