Serverless Shell Scripting: Integrating with AWS Lambda Custom Runtimes

AWS Lambda is a serverless computing service that allows you to run code without provisioning or managing servers. While Lambda supports various programming languages out of the box, such as Python, Node.js, and Java, you can also extend its capabilities by using custom runtimes.

https://docs.aws.amazon.com/lambda/latest/dg/lambda-runtimes.html

Custom runtimes enable you to bring your own base execution environment, making it possible to run bash scripts or commands directly within your Lambda functions, without the need for an intermediary programming language.

Setting up a Custom Runtime for Bash

To run bash commands in AWS Lambda, we need to create a custom runtime that includes the necessary components. Here's a step-by-step guide:

In the Lambda console try creating a new function and in the runtime choose

Amazon Linux 2023        

?Give function a name. For example, bash-executor and create function. In the generated skeleton rename the file to remove .sample in the extension. For the file named bootstrap remove all extension. Below is a screenshot of the function

Modify the shell script, here hello.sh to execute shell commands. In this example, we will print Welcome message to the user taking the input of person's name.

function handler () {
    EVENT_DATA=$1
    # Extract the value of the "name" key from the JSON input
    name=$(echo "$1" | sed -n 's/^.*"name":\s*"\([^"]*\)".*/\1/p')
    # Check if the "name" key exists in the JSON input
    if [ -z "$name" ]; then
      name="user"
    fi
    greetings="Welcome: $name"
    
    RESPONSE="{\"statusCode\": 200, \"body\": \"$greetings\"}"
    echo $RESPONSE
}
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Considerations and Best Practices:

When running bash scripts in AWS Lambda with a custom runtime, consider the following best practices:

1. Lambda Limits: Be aware of the Lambda execution limits, such as maximum execution time and memory allocation, and ensure that your bash script and custom runtime comply with these limits.

2. Security and Permissions: Review and grant the necessary permissions and security configurations for your Lambda function and custom runtime to access other AWS services or resources required by your bash script.

3. Monitoring and Logging: Implement proper monitoring and logging mechanisms to track the execution and performance of your Lambda function, custom runtime, and bash script.

4. Testing and Debugging: Test your bash script and custom runtime thoroughly in a local environment before deploying to AWS Lambda. Additionally, leverage the AWS Lambda Test Events feature for debugging and testing purposes.

5. Custom Runtime Maintenance: Keep your custom runtime up-to-date with the latest security patches and updates to ensure optimal performance and security.

Conclusion:

Running bash scripts in AWS Lambda with a custom runtime provides flexibility and extends the capabilities of serverless computing to a wider range of use cases. By following the steps outlined in this blog post and considering the nuances and best practices, you can successfully deploy and execute bash scripts in AWS Lambda using a custom runtime. Remember to monitor your Lambda function's performance, security, and costs, and leverage the various AWS services and tools to enhance your serverless workflow