Here we are going to see the basic Python AWS Lambda Hello World example using SAM (Serverless Application Model)
Prerequisites:
SAM uses AWS-CLI so its required to install AWS CLI to work with SAM, after all the above installations, we have to set up the AWS credentials, it varies based on your OS type we have an exclusive article for this or you can configure the credentials directly like below.
Python AWS SAM Lambda Example
I am working on the below versions:
$ sam --version
SAM CLI, version 1.23.0
$ aws --version
aws-cli/2.0.30 Python/3.7.4 Darwin/19.6.0 botocore/2.0.0dev34
Configure AWS Credentials:
The AWS configure command is used to map the AWS Account with the installed AWS CLI, that way the CLI can get access with your AWS Account.
$aws configure
$ aws configure
AWS Access Key ID [****************OE7N]: your_aws_access_key
AWS Secret Access Key [****************7qwh]: your_aws_secret_access_key
Default region name [None]: us-west-2
Default output format [None]:
Create SAM Project:
sam init command is used to generate the SAM project structure. For this example, I have generated the Sam project with python3.8 however, when implementing the code, we can change it to various versions of Python3x, .NET, Go, Node.js, Java or Ruby.
$sam init –runtime python3.8
$ sam init --runtime python3.8
Which template source would you like to use?
1 - AWS Quick Start Templates
2 - Custom Template Location
Choice: 1
What package type would you like to use?
1 - Zip (artifact is a zip uploaded to S3)
2 - Image (artifact is an image uploaded to an ECR image repository)
Package type: 1
Project name [sam-app]: hello-world-sam
Cloning app templates from https://github.com/aws/aws-sam-cli-app-templates
AWS quick start application templates:
1 - Hello World Example
2 - EventBridge Hello World
3 - EventBridge App from scratch (100+ Event Schemas)
4 - Step Functions Sample App (Stock Trader)
5 - Elastic File System Sample App
Template selection: 1
-----------------------
Generating application:
-----------------------
Name: hello-world-sam
Runtime: python3.8
Dependency Manager: pip
Application Template: hello-world
Output Directory: .
Next steps can be found in the README file at ./hello-world-sam/README.md
Project structure:
hello-world-sam $
.
├── README.md
├── __init__.py
├── events
│ └── event.json
├── hello_world
│ ├── __init__.py
│ ├── app.py
│ └── requirements.txt
├── template.yaml
└── tests
├── __init__.py
├── integration
│ ├── __init__.py
│ └── test_api_gateway.py
├── requirements.txt
└── unit
├── __init__.py
└── test_handler.py
Among all of the above files the most important file that we need to work on is app.py, it is the python lambda function.
The template.yaml is the one that has the SAM template.
The event.json has the sample event for testing.
The requirement.txt specifies the lambda function dependencies.
template.yaml
AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: >
hello-world-sam
Sample SAM Template for hello-world-sam
# More info about Globals: https://github.com/awslabs/serverless-application-model/blob/master/docs/globals.rst
Globals:
Function:
Timeout: 3
Resources:
HelloWorldFunction:
Type: AWS::Serverless::Function # More info about Function Resource: https://github.com/awslabs/serverless-application-model/blob/master/versions/2016-10-31.md#awsserverlessfunction
Properties:
CodeUri: hello_world/
Handler: app.lambda_handler
Runtime: python3.8
Events:
HelloWorld:
Type: Api # More info about API Event Source: https://github.com/awslabs/serverless-application-model/blob/master/versions/2016-10-31.md#api
Properties:
Path: /hello
Method: get
Outputs:
# ServerlessRestApi is an implicit API created out of Events key under Serverless::Function
# Find out more about other implicit resources you can reference within SAM
# https://github.com/awslabs/serverless-application-model/blob/master/docs/internals/generated_resources.rst#api
HelloWorldApi:
Description: "API Gateway endpoint URL for Prod stage for Hello World function"
Value: !Sub "https://${ServerlessRestApi}.execute-api.${AWS::Region}.amazonaws.com/Prod/hello/"
HelloWorldFunction:
Description: "Hello World Lambda Function ARN"
Value: !GetAtt HelloWorldFunction.Arn
HelloWorldFunctionIamRole:
Description: "Implicit IAM Role created for Hello World function"
Value: !GetAtt HelloWorldFunctionRole.Arn
The above simple template file used to build the AWS Lambda using SAM
app.py
import json
def lambda_handler(event, context):
"""Sample pure Lambda function
return {
"statusCode": 200,
"body": json.dumps({
"message": "hello world",
# "location": ip.text.replace("\n", "")
}),
}
Build the application
$sam build
hello-world-sam $ sam build
Building codeuri: /hello-world-sam/hello_world runtime: python3.8 metadata: {} functions: ['HelloWorldFunction']
Running PythonPipBuilder:ResolveDependencies
Running PythonPipBuilder:CopySource
Build Succeeded
Built Artifacts : .aws-sam/build
Built Template : .aws-sam/build/template.yaml
Commands you can use next
=========================
[*] Invoke Function: sam local invoke
[*] Deploy: sam deploy --guided
deploy the application
$sam deploy –guided
$ sam deploy --guided
Configuring SAM deploy
======================
Looking for config file [samconfig.toml] : Not found
Setting default arguments for 'sam deploy'
=========================================
Stack Name [sam-app]: hello-world-sam-application
AWS Region [us-west-2]: us-west-2
#Shows you resources changes to be deployed and require a 'Y' to initiate deploy
Confirm changes before deploy [y/N]: y
#SAM needs permission to be able to create roles to connect to the resources in your template
Allow SAM CLI IAM role creation [Y/n]: y
HelloWorldFunction may not have authorization defined, Is this okay? [y/N]: y
Save arguments to configuration file [Y/n]: y
SAM configuration file [samconfig.toml]:
SAM configuration environment [default]: dev
Looking for resources needed for deployment: Found!
Managed S3 bucket: aws-sam-cli-managed-default-samclisourcebucket-vlxz3w3to6ye
A different default S3 bucket can be set in samconfig.toml
Saved arguments to config file
Running 'sam deploy' for future deployments will use the parameters saved above.
The above parameters can be changed by modifying samconfig.toml
Learn more about samconfig.toml syntax at
https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/serverless-sam-cli-config.html
Uploading to hello-world-sam-application/58ec98812dacd95efee12c7e720890f1 585177 / 585177 (100.00%)
Deploying with following values
===============================
Stack name : hello-world-sam-application
Region : us-west-2
Confirm changeset : True
Deployment s3 bucket : aws-sam-cli-managed-default-samclisourcebucket-vlxz3w3to6ye
Capabilities : ["CAPABILITY_IAM"]
Parameter overrides : {}
Signing Profiles : {}
Initiating deployment
=====================
Uploading to hello-world-sam-application/b78c4ab547b82834a429f1f54a09b62f.template 1125 / 1125 (100.00%)
Waiting for changeset to be created..
CloudFormation stack changeset
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Operation LogicalResourceId ResourceType Replacement
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+ Add HelloWorldFunctionHelloWorldPermissionProd AWS::Lambda::Permission N/A
+ Add HelloWorldFunctionRole AWS::IAM::Role N/A
+ Add HelloWorldFunction AWS::Lambda::Function N/A
+ Add ServerlessRestApiDeployment47fc2d5f9d AWS::ApiGateway::Deployment N/A
+ Add ServerlessRestApiProdStage AWS::ApiGateway::Stage N/A
+ Add ServerlessRestApi AWS::ApiGateway::RestApi N/A
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Changeset created successfully. arn:aws:cloudformation:us-west-2:816569674899:changeSet/samcli-deploy1622384684/659cd0b5-e7fb-4767-a161-df496376c15e
Previewing CloudFormation changeset before deployment
======================================================
Deploy this changeset? [y/N]: y
2021-05-30 19:55:02 - Waiting for stack create/update to complete
CloudFormation events from changeset
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
ResourceStatus ResourceType LogicalResourceId ResourceStatusReason
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
CREATE_IN_PROGRESS AWS::IAM::Role HelloWorldFunctionRole Resource creation Initiated
CREATE_IN_PROGRESS AWS::IAM::Role HelloWorldFunctionRole -
CREATE_COMPLETE AWS::IAM::Role HelloWorldFunctionRole -
CREATE_IN_PROGRESS AWS::Lambda::Function HelloWorldFunction -
CREATE_COMPLETE AWS::Lambda::Function HelloWorldFunction -
CREATE_IN_PROGRESS AWS::Lambda::Function HelloWorldFunction Resource creation Initiated
CREATE_IN_PROGRESS AWS::ApiGateway::RestApi ServerlessRestApi -
CREATE_IN_PROGRESS AWS::ApiGateway::RestApi ServerlessRestApi Resource creation Initiated
CREATE_COMPLETE AWS::ApiGateway::RestApi ServerlessRestApi -
CREATE_IN_PROGRESS AWS::ApiGateway::Deployment ServerlessRestApiDeployment47fc2d5f9d Resource creation Initiated
CREATE_IN_PROGRESS AWS::Lambda::Permission HelloWorldFunctionHelloWorldPermissionProd Resource creation Initiated
CREATE_IN_PROGRESS AWS::Lambda::Permission HelloWorldFunctionHelloWorldPermissionProd -
CREATE_IN_PROGRESS AWS::ApiGateway::Deployment ServerlessRestApiDeployment47fc2d5f9d -
CREATE_COMPLETE AWS::ApiGateway::Deployment ServerlessRestApiDeployment47fc2d5f9d -
CREATE_IN_PROGRESS AWS::ApiGateway::Stage ServerlessRestApiProdStage Resource creation Initiated
CREATE_IN_PROGRESS AWS::ApiGateway::Stage ServerlessRestApiProdStage -
CREATE_COMPLETE AWS::ApiGateway::Stage ServerlessRestApiProdStage -
CREATE_COMPLETE AWS::Lambda::Permission HelloWorldFunctionHelloWorldPermissionProd -
CREATE_COMPLETE AWS::CloudFormation::Stack hello-world-sam-application -
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
CloudFormation outputs from deployed stack
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Outputs
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Key HelloWorldFunctionIamRole
Description Implicit IAM Role created for Hello World function
Value arn:aws:iam::816569674899:role/hello-world-sam-application-HelloWorldFunctionRole-NAYYRTABIVUF
Key HelloWorldApi
Description API Gateway endpoint URL for Prod stage for Hello World function
Value https://6v73c82ade.execute-api.us-west-2.amazonaws.com/Prod/hello/
Key HelloWorldFunction
Description Hello World Lambda Function ARN
Value arn:aws:lambda:us-west-2:816569674899:function:hello-world-sam-application-HelloWorldFunction-dAjHSaNEq6pl
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Successfully created/updated stack - hello-world-sam-application in us-west-2
If everything went well you can see the above success message.
Verify:
Login to your AWS account-> Switch to Lambda-> Select the lambda-> Code Source-> Run
References:
Happy Learning 🙂
