Learning About Lambda

Amazon Web Service’s serverless compute has always fascinated me. A lot of my pursuits of learning the DevOps methodology involves scripting but not full blown programming. When it comes to automation I can accomplish my goals with scripting. Now I just found out that you can run PowerShell in AWS Lambda but I think that is pretty recent. So before I knew that I decided I wanted to re-engage my brain centers for learning a programming language. I see a lot of hype and support for Google’s Go language. I started going through the tutorials and creating things. An idea came to me for a creation which I will talk about in a later post. For now I wanted to share my understanding of Lambda.

Lamba uses requests and events. The request contains the data it needs to function in kind of a HTTP post, at least that’s what it reminds me of since you can call it through a HTTP request and the Lambda library pulls out headers and the body. Then it returns in an HTTP fashion as well. Here’s a sample piece of code that leverages AWS Simple Email Service to take a name out of a HTTP body.

package main

import (
	"errors"
	"fmt"
	"log"

	"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/awserr"
	"github.com/aws/aws-sdk-go/aws/credentials"
	"github.com/aws/aws-sdk-go/aws/session"
	"github.com/aws/aws-sdk-go/service/ses"
)

const (
	// Replace sender@example.com with your "From" address.
	// This address must be verified with Amazon SES.
	Sender = "lambda@serverhobbyist.net"

	// Replace recipient@example.com with a "To" address. If your account
	// is still in the sandbox, this address must be verified.
	Recipient    = "Recipient@Recipient.com"

	// Specify a configuration set. To use a configuration
	// set, comment the next line and line 92.
	//ConfigurationSet = "ConfigSet"

	// The subject line for the email.
	Subject = "Lambda Function Go!"

	// The character encoding for the email.
	CharSet = "UTF-8"
)

var (
	// ErrNameNotProvided is thrown when a name is not provided
	ErrNameNotProvided = errors.New("no name was provided in the HTTP body")
)

// Handler is your Lambda function handler
// It uses Amazon API Gateway request/responses provided by the aws-lambda-go/events package,
// However you could use other event sources (S3, Kinesis etc), or JSON-decoded primitive types such as 'string'.
func Handler(request events.APIGatewayProxyRequest) (events.APIGatewayProxyResponse, error) {
	var TextBody = "Hello " + request.Body
	var HtmlBody = "Hello " + request.Body
	sess, err := session.NewSession(&aws.Config{
		Region:      aws.String("us-east-1"),
		Credentials: credentials.NewStaticCredentials("Removed", "Removed", ""),
	})

	// Create an SES session.
	svc := ses.New(sess)

	// Assemble the email.
	input := &ses.SendEmailInput{
		Destination: &ses.Destination{
			CcAddresses: []*string{},
			ToAddresses: []*string{
				aws.String(Recipient),
			},
			BccAddresses: []*string{
				aws.String(BCCRecipient),
			},
		},
		Message: &ses.Message{
			Body: &ses.Body{
				Html: &ses.Content{
					Charset: aws.String(CharSet),
					Data:    aws.String(HtmlBody),
				},
				Text: &ses.Content{
					Charset: aws.String(CharSet),
					Data:    aws.String(TextBody),
				},
			},
			Subject: &ses.Content{
				Charset: aws.String(CharSet),
				Data:    aws.String(Subject),
			},
		},
		Source: aws.String(Sender),
		// Uncomment to use a configuration set
		//ConfigurationSetName: aws.String(ConfigurationSet),
	}

	// Attempt to send the email.
	result, err := svc.SendEmail(input)
	log.Println(result)

	// Display error messages if they occur.
	if err != nil {
		if aerr, ok := err.(awserr.Error); ok {
			switch aerr.Code() {
			case ses.ErrCodeMessageRejected:
				fmt.Println(ses.ErrCodeMessageRejected, aerr.Error())
			case ses.ErrCodeMailFromDomainNotVerifiedException:
				fmt.Println(ses.ErrCodeMailFromDomainNotVerifiedException, aerr.Error())
			case ses.ErrCodeConfigurationSetDoesNotExistException:
				fmt.Println(ses.ErrCodeConfigurationSetDoesNotExistException, aerr.Error())
			default:
				fmt.Println(aerr.Error())
			}
		} else {
			// Print the error, cast err to awserr.Error to get the Code and
			// Message from an error.
			fmt.Println(err.Error())
		}

	}

	// stdout and stderr are sent to AWS CloudWatch Logs
	log.Printf("Processing Lambda request %s\n", request.RequestContext.RequestID)

	// If no name is provided in the HTTP request body, throw an error
	if len(request.Body) < 1 {
		return events.APIGatewayProxyResponse{}, ErrNameNotProvided
	}
	log.Println(request.PathParameters)
	return events.APIGatewayProxyResponse{
		Body:       "Hello " + request.Body,
		StatusCode: 200,
	}, nil

}

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