Supporting Multiple Triggers for AWS Lambda in Golang

Introduction

AWS Lambda supports triggering functions from various sources, including S3 events and SQS messages. However, when you require your Lambda function to respond to multiple triggers, a dilemma arises.

Proposed Solutions

You attempted two approaches:

First Approach:

func main() {
    lambda.Start(ProcessIncomingS3Events)
    lambda.Start(ProcessIncomingEvents)
}

This method failed because the first trigger (ProcessIncomingS3Events) would always handle all events.

Second Approach:

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

In this scenario, Lambda could not identify the event type, resulting in "Could not find the event type" errors for all triggers.

Multi-Event Handler Implementation

To overcome these limitations, you can implement a multi-event handler using the AWS Handler interface. Here's a sample implementation:

type Handler struct {
    // Define global variables or context information
}

func (h Handler) Invoke(ctx context.Context, data []byte) ([]byte, error) {
    // Unmarshal the data based on different event types

    var apiGatewayEvent events.APIGatewayProxyRequest
    if err := json.Unmarshal(data, &apiGatewayEvent); err == nil {
        // Handle API Gateway event
    }

    var snsEvent events.SNSEvent
    if err := json.Unmarshal(data, &snsEvent); err == nil {
        // Handle SNS event
    }

    return nil, nil
}

func main() {
    lambda.StartHandler(Handler{})
}

With this approach, your Lambda function can listen to various AWS events and handle them accordingly.

Considerations

While using this method provides flexibility, remember that Lambda functions are designed to handle a single type of event effectively. Mixing multiple event types may introduce complexities and performance issues.