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Hello World

This is a simple example of an AWS Lambda function that takes a String as input parameter and returns a String as response.

Code

The code creates a LambdaRuntime struct. In it's simplest form, the initializer takes a function as argument. The function is the handler that will be invoked when an event triggers the Lambda function.

The handler is (event: String, context: LambdaContext). The function takes two arguments:

  • the event argument is a String. It is the parameter passed when invoking the function.
  • the context argument is a Lambda Context. It is a description of the runtime context.

The function return value will be encoded as your Lambda function response.

Test locally

You can test your function locally before deploying it to AWS Lambda.

To start the local function, type the following commands:

swift run

It will compile your code and start the local server. You know the local server is ready to accept connections when you see this message.

Building for debugging...
[1/1] Write swift-version--644A47CB88185983.txt
Build of product 'MyLambda' complete! (0.31s)
2025-01-29T12:44:48+0100 info LocalServer : host="127.0.0.1" port=7000 [AWSLambdaRuntime] Server started and listening

Then, from another Terminal, send your payload with curl. Note that the payload must be a valid JSON string. In the case of this function that accepts a simple String, it means the String must be wrapped in between double quotes.

curl -d '"seb"' http://127.0.0.1:7000/invoke    
"Hello seb"

Important

The local server is only available in DEBUG mode. It will not start with swift -c release run.

Build & Package

To build & archive the package, type the following commands.

swift package --allow-network-connections docker lambda-build

If there is no error, there is a ZIP file ready to deploy. The ZIP file is located at .build/plugins/AWSLambdaBuilder/outputs/AWSLambdaBuilder/MyLambda/MyLambda.zip

Deploy

Here is how to deploy using the lambda-deploy plugin.

swift package --allow-network-connections all:443 lambda-deploy

This creates the Lambda function, provisions the necessary IAM role, and uploads the deployment package.

Invoke your Lambda function

To invoke the Lambda function, use this aws command line.

aws lambda invoke \
--function-name MyLambda \
--payload $(echo \"Seb\" | base64)  \
out.txt && cat out.txt && rm out.txt

Note that the payload is expected to be a valid JSON string, hence the surroundings quotes (").

This should output the following result.

{
    "StatusCode": 200,
    "ExecutedVersion": "$LATEST"
}
"Hello Seb"

Undeploy

When done testing, you can delete the Lambda function with this command.

swift package --allow-network-connections all:443 lambda-deploy --delete

⚠️ Security and Reliability Notice

These are example applications for demonstration purposes. When deploying such infrastructure in production environments, we strongly encourage you to follow these best practices for improved security and resiliency: