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Lambda S3

Upload, Download, or Delete files from AWS S3 with one function through AWS Lambda and AWS APIGateway.

How to Build locally

  1. make build

How to Test locally

  1. cp .env.example .env copy the example .env file to use as a base
  2. nano .env insert real values for each environment variable
  3. make test

How to Use

  1. go get github.com/seantcanavan/lambda_s3@latest
  2. import github.com/seantcanavan/lambda_s3
  3. Get the file headers uploaded via AWS Lambda / API Gateway: headers, err := lambda_s3.GetHeaders()
    1. Make sure to check the value of APIGatewayProxyRequest.IsBase64Encoded and make sure it matches the form body contents
  4. Upload the uploaded file contents via the file headers: lambda_s3.UploadHeader(header[0], region, bucket, name)
  5. Download the file contents via the file's bucket/key combination: lambda_s3.Download()
  6. Use errors.Is to check for different error cases returned from GetHeaders, UploadHeader, Download, and Delete
    1. Check below for sample code on how to implement the functions and use errors.Is
  7. Delete the uploaded file via the values returned from Upload: lambda_s3.Delete(region, bucket,name)

Sample Upload Lambda Handler Example

func UploadLambda(ctx context.Context, lambdaReq events.APIGatewayProxyRequest) (events.APIGatewayProxyResponse, error) {
	// get the file header and multipart form data from Lambda
	files, err := lambda_s3.GetFileHeadersFromLambdaReq(lambdaReq, MaxFileSizeBytes)
	if err != nil {
		switch {
		case
			errors.Is(err, lambda_s3.ErrContentTypeHeaderMissing),
			errors.Is(err, lambda_s3.ErrParsingMediaType),
			errors.Is(err, lambda_s3.ErrBoundaryValueMissing):
			return ERROR - bad request
		default:
			return ERROR - internal server
		}
	}

	fileName := uuid.New().String() // generate a UUID for filename to guarantee uniqueness

	// take the first file uploaded via HTTP and upload it to S3
	// you can also loop through all the files in files to upload each individually:
	// for _, currentFile := range files { Upload... }
	uploadResult, err := lambda_s3.UploadFileHeaderToS3(files[0], os.Getenv("REGION_AWS"), os.Getenv("FILE_BUCKET"), fileName)
	if err != nil {
		switch {
		case
			errors.Is(err, lambda_s3.ErrParameterRegionEmpty),
			errors.Is(err, lambda_s3.ErrParameterBucketEmpty),
			errors.Is(err, lambda_s3.ErrParameterNameEmpty):
			return ERROR - bad request
		default:
			return ERROR - internal server
		}
	}

	return events.APIGatewayProxyResponse{
		StatusCode: http.StatusOK,
		Body:            "",
	}, nil
}

Sample Download Lambda Handler Example

func DownloadLambda(ctx context.Context, lambdaReq events.APIGatewayProxyRequest) (events.APIGatewayProxyResponse, error) {
	fileID := lambdaReq.PathParameters["id"]
	if fileID == "" {
		return ERROR - bad request
	}

	file, err := GetFileByID(ctx, fileID) // get the file object from your database to retrieve its unique name
	if err != nil {
		return ERROR - not found
	}

	fileBytes, err := lambda_s3.DownloadFileFromS3(os.Getenv("REGION_AWS"), os.Getenv("FILE_BUCKET"), file.Name)
	if err != nil {
		switch {
		case
			errors.Is(err, lambda_s3.ErrParameterRegionEmpty),
			errors.Is(err, lambda_s3.ErrParameterBucketEmpty),
			errors.Is(err, lambda_s3.ErrParameterNameEmpty),
			errors.Is(err, lambda_s3.ErrEmptyFileDownloaded):
			return ERROR - bad request
		default:
			return ERROR - internal server
		}
	}

	return events.APIGatewayProxyResponse{
		StatusCode: http.StatusOK,
		Headers: map[string]string{
			"Content-Type": file.ContentType,
		},
		Body:            base64.StdEncoding.EncodeToString(fileBytes),
		IsBase64Encoded: true,
	}, nil
}

All tests are passing

=== RUN   TestDelete
--- PASS: TestDelete (0.43s)
=== RUN   TestDownloadFileFromS3
=== RUN   TestDownloadFileFromS3/verify_err_when_region_is_empty
=== RUN   TestDownloadFileFromS3/verify_err_when_bucket_is_empty
=== RUN   TestDownloadFileFromS3/verify_err_when_name_is_empty
=== RUN   TestDownloadFileFromS3/verify_err_when_region_is_invalid
=== RUN   TestDownloadFileFromS3/verify_err_when_target_file_is_empty
=== RUN   TestDownloadFileFromS3/verify_download_works_with_correct_inputs
--- PASS: TestDownloadFileFromS3 (0.62s)
    --- PASS: TestDownloadFileFromS3/verify_err_when_region_is_empty (0.00s)
    --- PASS: TestDownloadFileFromS3/verify_err_when_bucket_is_empty (0.00s)
    --- PASS: TestDownloadFileFromS3/verify_err_when_name_is_empty (0.00s)
    --- PASS: TestDownloadFileFromS3/verify_err_when_region_is_invalid (0.48s)
    --- PASS: TestDownloadFileFromS3/verify_err_when_target_file_is_empty (0.10s)
    --- PASS: TestDownloadFileFromS3/verify_download_works_with_correct_inputs (0.05s)
=== RUN   TestGetFileHeadersFromLambdaReq
=== RUN   TestGetFileHeadersFromLambdaReq/verify_err_when_Content-Type_header_not_set
=== RUN   TestGetFileHeadersFromLambdaReq/verify_err_when_content_type_is_invalid
=== RUN   TestGetFileHeadersFromLambdaReq/verify_err_when_content_type_has_no_boundary_value
=== RUN   TestGetFileHeadersFromLambdaReq/verify_get_headers_works_with_correct_inputs
--- PASS: TestGetFileHeadersFromLambdaReq (0.00s)
    --- PASS: TestGetFileHeadersFromLambdaReq/verify_err_when_Content-Type_header_not_set (0.00s)
    --- PASS: TestGetFileHeadersFromLambdaReq/verify_err_when_content_type_is_invalid (0.00s)
    --- PASS: TestGetFileHeadersFromLambdaReq/verify_err_when_content_type_has_no_boundary_value (0.00s)
    --- PASS: TestGetFileHeadersFromLambdaReq/verify_get_headers_works_with_correct_inputs (0.00s)
=== RUN   TestUploadFileHeaderToS3
=== RUN   TestUploadFileHeaderToS3/verify_err_when_region_is_empty
=== RUN   TestUploadFileHeaderToS3/verify_err_when_bucket_is_empty
=== RUN   TestUploadFileHeaderToS3/verify_err_when_name_is_empty
=== RUN   TestUploadFileHeaderToS3/verify_err_when_*multipart.FileHeader_is_empty
=== RUN   TestUploadFileHeaderToS3/verify_err_when_region_is_invalid_and_upload_fails
=== RUN   TestUploadFileHeaderToS3/verify_upload_works_with_correct_inputs
--- PASS: TestUploadFileHeaderToS3 (0.78s)
    --- PASS: TestUploadFileHeaderToS3/verify_err_when_region_is_empty (0.00s)
    --- PASS: TestUploadFileHeaderToS3/verify_err_when_bucket_is_empty (0.00s)
    --- PASS: TestUploadFileHeaderToS3/verify_err_when_name_is_empty (0.00s)
    --- PASS: TestUploadFileHeaderToS3/verify_err_when_*multipart.FileHeader_is_empty (0.00s)
    --- PASS: TestUploadFileHeaderToS3/verify_err_when_region_is_invalid_and_upload_fails (0.71s)
    --- PASS: TestUploadFileHeaderToS3/verify_upload_works_with_correct_inputs (0.07s)
PASS
ok  	github.com/seantcanavan/lambda_s3	1.838s