lambda_s3

Lambda S3

Upload or Download 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.GetFileHeadersFromLambdaReq()
4. Upload the uploaded file contents via the file headers: lambda_s3.UploadFileHeaderToS3()
5. Download the file contents via the file's bucket/key combination: lambda_s3.DownloadFileFromS3()
6. Use errors.Is to check for different error cases returned from GetFileHeadersFromLambdaReq, UploadFileHeaderToS3, and DownloadFileFromS3
   1. Check below for sample code on how to implement the functions and use errors.Is

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

 func TestDownloadFileFromS3(t *testing.T) {
Thu Jan 19 05:39 PM lambda_s3: make test
go test -v
=== 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   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 (0.99s)
    --- 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 (0.57s)
    --- PASS: TestDownloadFileFromS3/verify_err_when_target_file_is_empty (0.32s)
    --- PASS: TestDownloadFileFromS3/verify_download_works_with_correct_inputs (0.10s)
=== 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 (0.55s)
    --- 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 (0.49s)
    --- PASS: TestUploadFileHeaderToS3/verify_upload_works_with_correct_inputs (0.06s)
PASS
ok  	github.com/seantcanavan/lambda_s3	1.538s