A/B Testing AI Model Versions with AWS Lambda Alias

Question

Pulumi · Accepted Answer

A/B testing is a method to compare two versions of a single variable to determine which performs better. In AWS Lambda, you can implement A/B testing by using Lambda Aliases and weighted routing. An alias is a pointer to a specific Lambda function version. You can associate a portion of your traffic to go to one version of a function and the rest to another version using weighted routing, allowing you to perform the A/B testing.

Below is a program that uses Pulumi to create an AWS Lambda function, publishes two versions of this function, and sets up an alias to route traffic between them for A/B testing.

First, you would create a Lambda function. Then you would publish two versions of this function. After publishing the versions, you create an alias (`myLambdaAlias`) that points to the first version by default. Finally, you configure `routingConfig` with `additionalVersionWeights` to send a portion of the traffic to the second version for A/B testing.

```python
import pulumi
import pulumi_aws as aws

# Create an AWS Lambda function
lambda_func = aws.lambda_.Function("myLambdaFunction",
    runtime="python3.8",
    code=pulumi.FileArchive("./function.zip"),  # Assuming you have a ZIP file of your Lambda code
    handler="index.handler",  # The function within your code that Lambda calls to start execution
    role=my_lambda_role.arn  # IAM role with permissions for the Lambda Function
)

# Publish a new version of the Lambda function
version1 = aws.lambda_.Function("version1",
    s3_bucket="my-bucket",
    s3_key="lambda_function_payload.zip",
    function_name=lambda_func.name
)

version2 = aws.lambda_.Function("version2",
    s3_bucket="my-bucket",
    s3_key="lambda_function_payload_v2.zip",
    function_name=lambda_func.name
)

# Create a Lambda alias and map it to the Lambda function's first version
lambda_alias = aws.lambda_.Alias("myLambdaAlias",
    function_name=lambda_func.name,
    function_version=version1.version,  # Pointing alias to version 1 of the function
    description="My Lambda Alias for A/B Testing",
    routing_config={
        "additional_version_weights": {
            version2.version: 0.5  # Routing 50% traffic to version 2 for A/B testing
        }
    }
)

# Export the Lambda Alias ARN to access it later
pulumi.export('alias_arn', lambda_alias.arn)
```

This program starts by creating an AWS Lambda function using the `aws.lambda_.Function` class, indicating the runtime, code source, handler, and IAM role. The `pulumi.FileArchive` class is used to specify the ZIP archive containing the Lambda function code.

We publish two separate versions of the Lambda function, each potentially with a different `s3_key` indicating a different code payload. These versions represent the two variations of our AI model that we want to test against each other.

Next, we use the `aws.lambda_.Alias` class to create an alias that points to one of the versions of the Lambda function. We set up the weighted routing by specifying `additional_version_weights` in the alias configuration. This is where we actually implement the A/B testing mechanism by directing a fraction of the invocation traffic to a different function version.

Finally, we export the ARN of the Lambda alias using `pulumi.export`, allowing us to identify and invoke the alias outside of the Pulumi application if necessary.

You can adjust the percentage of traffic going to each version by changing the weights in the `additional_version_weights` dictionary. Please note that the AWS IAM role (`my_lambda_role.arn`) is referenced, but its definition is not included in this program. You need an IAM role that the Lambda function can assume with the appropriate permissions set up separately.