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Serverless Application Model - Executing Lambdas Locally
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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 @spicykey
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- 5. HOW DO I RUN A LAMBDA FUNCTION LOCALLY? • Install aws-sam-local • Create a ServerlessApplication Model (SAM) template file in YAML or JSON • In your favorite shell, execute ‘sam local invoke’ @spicykey
- 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 @spicykey
- 7. LOCAL DYNAMODB + LOCAL LAMBDA • Run DynamoDBon 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'}); @spicykey
- 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: ‘npmstart’ 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. @spicykey
- 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 ‘samlocal invoke –e sample-event.json’ @spicykey
- 10. SCENARIO – S3 EVENT DEVELOPMENT • Example: A developer has a javascriptbased 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.’ @spicykey
- 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 @spicykey
- 12. THANK YOU – ABOUT ME • #Serverless •#Alexa • #Code @spicykey SpicyKey LLC develops apps for clients https://spicykey.com https://youtube.com/spicykey