AWS Lambda to publish an AWS Health event on an AWS SNS topic

lambda_sns_publish.go

package main

import (
	"context"
	"encoding/json"
	"fmt"
	"log"
	"os"
	"strings"

	"github.com/aws/aws-lambda-go/events"
	"github.com/aws/aws-lambda-go/lambda"
	"github.com/aws/aws-sdk-go/aws"
	"github.com/aws/aws-sdk-go/aws/session"
	"github.com/aws/aws-sdk-go/service/sns"
)

var (
	sns_topic_arn string = os.Getenv("SNS_TOPIC_ARN")
	environment   string = os.Getenv("ENVIRONMENT")
)

type CloudWatchEventDetails struct {
	EventArn          string `json:"eventArn"`
	Service           string `json:"service"`
	EventTypeCode     string `json:"eventTypeCode"`
	EventTypeCategory string `json:"eventTypeCategory"`
	StartTime         string `json:"startTime"`
	EndTime           string `json:"endTime"`
	EventDescription  []struct {
		Language          string `json:"language"`
		LatestDescription string `json:"latestDescription"`
	} `json:"eventDescription"`
	AffectedEntities []struct {
		EntityValue string `json:"entityValue"`
		Tags        struct {
			Stage string `json:"stage"`
			App   string `json:"app"`
		} `json:"tags"`
	} `json:"affectedEntities"`
}
type SNSEventMessage struct {
	Default string `json:"default"`
}
type EventMessage struct {
	Description string   `json:"description"`
	StartTime   string   `json:"startTime"`
	EndTime     string   `json:"endTime"`
	Resources   []string `json:"resources"`
}

func handleRequest(ctx context.Context, event events.CloudWatchEvent) {
	fmt.Println("This is the JSON for event details", string(event.Detail))

	var eventDetails CloudWatchEventDetails

	// Unmarshal the event details
	err := json.Unmarshal(event.Detail, &eventDetails)
	if err != nil {
		log.Fatal(fmt.Errorf("unmarshal: %w", err))
	}

	fmt.Printf("This is the CloudWatchEvent: %+v\n", eventDetails)

	// Create SNS message info
	topicSubject := fmt.Sprintf("[AWS %s - %s] %s", eventDetails.Service, strings.Title(environment), eventDetails.EventTypeCode)
	eventMessage, err := json.Marshal(EventMessage{
		Description: eventDetails.EventDescription[0].LatestDescription,
		StartTime:   eventDetails.StartTime,
		EndTime:     eventDetails.EndTime,
		Resources:   event.Resources,
	})
	if err != nil {
		log.Fatal(fmt.Errorf("marshaling event message: %w", err))
	}
	snsMessage, err := json.Marshal(SNSEventMessage{
		Default: string(eventMessage),
	})
	if err != nil {
		log.Fatal(fmt.Errorf("marshaling sns event message: %w", err))
	}

	// Add SNS params
	snsPublishParams := &sns.PublishInput{
		Message:          aws.String(string(snsMessage)),
		MessageStructure: aws.String("json"),
		Subject:          aws.String(topicSubject),
		TopicArn:         aws.String(sns_topic_arn),
	}

	// Create AWS session
	sess := session.Must(session.NewSessionWithOptions(session.Options{
		SharedConfigState: session.SharedConfigEnable,
	}))

	// Create SNS client
	svc := sns.New(sess)

	// Publish SNS message
	pub, err := svc.Publish(snsPublishParams)
	if err != nil {
		log.Fatal("Error publishing message:", err)
		return
	}

	log.Print("MessageID:", *pub.MessageId)
}

// handleRequest is our lambda handler invoked by the `lambda.Start` function call
func main() {
	lambda.Start(handleRequest)
}