AWS SAM(Serverless Application Model) Python Lambda API application

This is the code for the Serverless backend I have created for my project on AWS lambda AWS Konsole.

Steps to deploy a SAM application

REQUIREMENTS:

AWS CLI already configured with Administrator permission
Python 3 installed
SAM CLI installed

Initialize a sample application

Initialize a sample application from a template using sam init --runtime <runtime_name> --name <app_name>

Similar structure will be created:

    ├── README.md                   <-- This instructions file
├── event.json                  <-- API Gateway Proxy Integration event payload
├── hello_world                 <-- Source code for a lambda function
│   ├── __init__.py
│   ├── app.py                  <-- Lambda function code
│   ├── requirements.txt        <-- Lambda function code
├── template.yaml               <-- SAM Template
└── tests                       <-- Unit tests
    └── unit
        ├── __init__.py
        └── test_handler.py

Local development

After doing the changes to the template you can test it locally

Invoking function locally using a local sample payload

sam local invoke HelloWorldFunction --event event.json

Invoking function locally through local API Gateway

sam local start-api

If the previous command ran successfully you should now be able to hit the following local endpoint to invoke your function http://localhost:3000/hello

SAM CLI is used to emulate both Lambda and API Gateway locally and uses our template.yaml to understand how to bootstrap this environment (runtime, where the source code is, etc.)

Creating a bucket for the templates

Firstly, we need a S3 bucket where we can upload our Lambda functions packaged as ZIP before we deploy anything - If you don't have a S3 bucket to store code artifacts then this is a good time to create one:

aws s3 mb s3://BUCKET_NAME

Packaging the template

Next, run the following command to package our Lambda function to S3:

sam package \
    --output-template-file packaged.yaml \
    --s3-bucket REPLACE_THIS_WITH_YOUR_S3_BUCKET_NAME

Deploying the template

Next, the following command will create a Cloudformation Stack and deploy your SAM resources.

sam deploy \
    --template-file packaged.yaml \
    --stack-name sam-awsapi \
    --capabilities CAPABILITY_IAM

Tips for python code

Python packages have to be installed in the path: /opt/python/lib/python3.6<3.7>/site-packages
Lambda-layers To use Lambda Layers use the following steps:
- Create a lambda_layers folder
- Create the following folder structure in this folder : lambda_layers/python/lib/python3.6/site-packages
- Create all the python files you want to create in the site-packages folder
- Install all the pip packages you need pip install -r requirements.txt -t <dir>
- Create a data folder if you need to use any JSON files
- zip all the folders and name it lambda-layers.zip
- in the template.yaml file mention this property in each serverless function:
```
Layers:
    - !Ref MyLambdaLayer
```

darshan-raul/SAM-Serverless-Application-Model-rest-api-lambda-