03_aws_lambda

AWS Lambda

This is a simple demonstration of how to create a serverless application using AWS Lambda.

• AWS Lambda
  • Features
  • Technologies
  • Setup

Features

This application has the following features:

• just returns a simple message.

Technologies

The application is built using the following technologies, libraries, frameworks, and tools:

• Go,
• AWS Lambda for Go,
• LocalStack 📖.

Setup

To run this application, you need to have the following installed on your system:

• Go,
• AWS CLI.

Of course, you also need an AWS account or a LocalStack instance running (requires Docker).

To install LocalStack, you can run the following command:

pip install localstack

To start LocalStack, you can run the following command:

localstack start -d

Alternatively, you can use the docker-compose file provided in this repository:

docker-compose up -d

If you want to use the AWS CLI with LocalStack, please follow this guide.

First you need to create a role for your lambda function. You can do this by running the following command:

aws iam create-role --role-name lambda-ex --assume-role-policy-document file://trust-policy.json

For LocalStack, you can need to add to every command the --endpoint-url=http://localhost:4566 flag (or define an alias awslocal for the AWS CLI with the same flag).

alias awslocal="aws --endpoint-url=http://localhost:4566"

Where trust-policy.json is a file with the following content:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Principal": {
        "Service": "lambda.amazonaws.com"
      },
      "Action": "sts:AssumeRole"
    }
  ]
}

Then you need to attach the AWSLambdaBasicExecutionRole policy to the role:

aws iam attach-role-policy --role-name lambda-ex --policy-arn arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole

Now you can build the application:

Windows:

set GOOS=linux
set GOARCH=amd64
go build -o bootstrap main.go

Linux:

GOOS=linux GOARCH=amd64 go build -o bootstrap main.go

And then you can create a zip file with the application:

Windows:

Compress-Archive -Path .\bootstrap -DestinationPath .\bootstrap.zip

Linux:

zip bootstrap.zip bootstrap

Then you can create the Lambda function (you need to replace the role ARN with the one you created):

aws lambda create-function --function-name aws-lambda --zip-file fileb://./bootstrap.zip --handler bootstrap --runtime provided.al2 --role arn:aws:iam::PUT_YOUR_ID_HERE:role/lambda-ex

To list the functions, you can run the following command:

aws lambda list-functions

Finally, you can invoke the function:

aws lambda invoke --invocation-type RequestResponse --function-name aws-lambda --cli-binary-format raw-in-base64-out --payload '{"What is your name?":"John Doe","What is your year of birth?":2000}' response.json

In the response.json file, you should see something like this:

{
  "message": "Hello, John Doe! You are 24 years old."
}

If you have received the time out error, you can increase the timeout for the function:

aws lambda update-function-configuration --function-name aws-lambda --timeout 300

Alternatively we can use:

aws lambda wait function-active --function-name aws-lambda

To remove the function, you can run the following command:

aws lambda delete-function --function-name aws-lambda

To remove the role, you can run the following command:

aws iam detach-role-policy --role-name lambda-ex --policy-arn arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole
aws iam delete-role --role-name lambda-ex