main.go

package main

import (
	"errors"
	"fmt"
	"strings"
	"time"

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

var (
	cwl *cloudwatchlogs.CloudWatchLogs

	userID = "Xe"
	data   = "Test in hope of harambe"
)

func main() {
	sess, err := session.NewSession(&aws.Config{Region: aws.String("us-west-2")})
	if err != nil {
		fmt.Println("failed to create session,", err)
		return
	}

	cwl = cloudwatchlogs.New(sess)

	err = createStreamIfNotExists(userID)
	if err != nil {
		panic(err)
	}

	sequenceToken, now, err := getSequenceToken(userID)
	if err != nil {
		panic(err)
	}

	err = submitLogMessage(string(data), userID, *sequenceToken, now)
	if err != nil {
		panic(err)
	}
}

func createStreamIfNotExists(userID string) error {
	csi := &cloudwatchlogs.CreateLogStreamInput{
		LogGroupName:  aws.String("userlogs"),
		LogStreamName: aws.String(userID),
	}

	_, err := cwl.CreateLogStream(csi)
	if err != nil {
		aerr, ok := err.(awserr.Error)
		if !ok {
			return err
		}

		if strings.HasPrefix(aerr.Code(), "ResourceAlreadyExistsException") {
			return nil
		}

		return err
	}

	return nil
}

func getSequenceToken(userID string) (*string, time.Time, error) {
	input := &cloudwatchlogs.DescribeLogStreamsInput{
		Limit:               aws.Int64(1),
		LogGroupName:        aws.String("userlogs"),
		LogStreamNamePrefix: aws.String(userID),
	}
	now := time.Now()

	logStreams, err := cwl.DescribeLogStreams(input)
	if err != nil {
		return aws.String(""), now, err
	}

	if len(logStreams.LogStreams) != 1 {
		return aws.String(""), now, errors.New("userlog: specified logging group does not exist")
	}

	token := logStreams.LogStreams[0].UploadSequenceToken

	return token, now, nil
}

func submitLogMessage(data, userID, sequenceToken string, now time.Time) error {
	logInput := &cloudwatchlogs.PutLogEventsInput{
		LogEvents: []*cloudwatchlogs.InputLogEvent{
			{
				Message:   aws.String(string(data)),
				Timestamp: aws.Int64(now.Unix()),
			},
			{
				Message:   aws.String("hi test please work thanks <3"),
				Timestamp: aws.Int64(now.Unix()),
			},
		},
		LogGroupName:  aws.String("userlogs"),
		LogStreamName: aws.String(userID),
		SequenceToken: aws.String(sequenceToken),
	}

	_, err := cwl.PutLogEvents(logInput)
	if err != nil {
		if strings.HasPrefix(err.Error(), "InvalidSequenceTokenException") {
			return submitLogMessage(data, userID, strings.Split(err.Error(), " ")[11], now)
		}

		return err
	}

	return nil
}