How can I detect a warm-up invocation in a Go AWS Lambda function using the Serverless WarmUp plugin?

Question

I'm using the Serverless WarmUp plugin to keep my Go AWS Lambda function warm. I need to detect when the Lambda function is invoked by the plugin so that I can return a specific response. How can I properly detect a warm-up invocation within my Go code?

Answer 1

You can detect a warm-up invocation in a Go AWS Lambda function by inspecting the client context, which can be done using the lambdacontext package from AWS Lambda's Go SDK. Here's a code snippet that shows how you can do this:

    package main

import (
    "context"
    "github.com/aws/aws-lambda-go/events"
    "github.com/aws/aws-lambda-go/lambda"
    "github.com/aws/aws-lambda-go/lambdacontext"
)

func HandleRequest(ctx context.Context, request events.APIGatewayProxyRequest) (events.APIGatewayProxyResponse, error) {
    lc, _ := lambdacontext.FromContext(ctx)
    if lc.ClientContext.Custom["source"] == "serverless-plugin-warmup" {
        return events.APIGatewayProxyResponse{Body: "Lambda is warm!", StatusCode: 200}, nil
    }

    // ... other function logic ...

    // Default response for demonstration
    return events.APIGatewayProxyResponse{
        StatusCode: 200,
        Body:       "Hello from Go Lambda!",
    }, nil
}

func main() {
    lambda.Start(HandleRequest)
}