Using Golang to Handle AWS SDK API Error Codes for REST API Responses

Handling HTTP Error Codes from AWS SDK Requests in Golang

Implementing modular Golang backend scripts to manage HTTP errors from AWS SDK

// Approach 1: Using a Mapping Table to Convert String Error Codes to HTTP Status Codes
package main

import (
    "errors"
    "fmt"
    "net/http"
    "github.com/aws/smithy-go"
)

// UsecaseError represents the custom error structure for JSON responses
type UsecaseError struct {
    Code    int    `json:"code"`
    Message string `json:"message"`
}

// Error satisfies the error interface for UsecaseError
func (e *UsecaseError) Error() string {
    return fmt.Sprintf(`{"code": %d, "message": "%s"}`, e.Code, e.Message)
}

// Map of AWS error codes to HTTP status codes
var errorCodeMapping = map[string]int{
    "NotAuthorizedException": http.StatusUnauthorized,
    "UserNotFoundException": http.StatusNotFound,
    "TooManyRequestsException": http.StatusTooManyRequests,
    "InternalErrorException": http.StatusInternalServerError,
    // Add additional mappings as necessary
}

// ConvertAWSAPIError handles AWS SDK errors and returns a UsecaseError
func ConvertAWSAPIError(err error) *UsecaseError {
    var apiErr smithy.APIError
    if errors.As(err, &apiErr) {
        code, exists := errorCodeMapping[apiErr.ErrorCode()]
        if exists {
            return &UsecaseError{
                Code:    code,
                Message: apiErr.ErrorMessage(),
            }
        }
    }
    // Default error response
    return &UsecaseError{
        Code:    http.StatusInternalServerError,
        Message: "An unknown error occurred",
    }
}

Converting AWS Error Codes with Type Assertions in Golang

Using Type Assertions for Improved Error Handling in Golang

package main

import (
    "errors"
    "fmt"
    "net/http"
    "github.com/aws/smithy-go"
)

// UsecaseError struct to hold HTTP code and message
type UsecaseError struct {
    Code    int    `json:"code"`
    Message string `json:"message"`
}

func (e *UsecaseError) Error() string {
    return fmt.Sprintf(`{"code": %d, "message": "%s"}`, e.Code, e.Message)
}

// AWSAPIErrorToHTTP maps APIError codes directly to HTTP status codes using type assertions
func AWSAPIErrorToHTTP(err error) *UsecaseError {
    var apiErr smithy.APIError
    if errors.As(err, &apiErr) {
        switch apiErr.ErrorCode() {
        case "NotAuthorizedException":
            return &UsecaseError{Code: http.StatusUnauthorized, Message: apiErr.ErrorMessage()}
        case "UserNotFoundException":
            return &UsecaseError{Code: http.StatusNotFound, Message: apiErr.ErrorMessage()}
        case "TooManyRequestsException":
            return &UsecaseError{Code: http.StatusTooManyRequests, Message: apiErr.ErrorMessage()}
        default:
            return &UsecaseError{Code: http.StatusInternalServerError, Message: apiErr.ErrorMessage()}
        }
    }
    return &UsecaseError{Code: http.StatusInternalServerError, Message: "Unknown error"}
}

Unit Tests for AWS API Error Conversion Functions

Testing functions to validate HTTP status code responses for different AWS API errors

package main

import (
    "errors"
    "testing"
    "net/http"
)

// Mock error types for testing
type mockAPIError struct{}

func (e *mockAPIError) ErrorCode() string {
    return "UserNotFoundException"
}

func (e *mockAPIError) ErrorMessage() string {
    return "User not found"
}

func TestConvertAWSAPIError(t *testing.T) {
    mockErr := &mockAPIError{}
    err := ConvertAWSAPIError(mockErr)
    if err.Code != http.StatusNotFound {
        t.Errorf("expected %d, got %d", http.StatusNotFound, err.Code)
    }
}

Common Questions on AWS SDK Error Handling in Golang

1. How can I retrieve HTTP status codes from AWS SDK errors?
2. In Golang, the AWS SDK errors are often returned as strings. By using a custom mapping or a switch statement, you can match error codes with relevant HTTP status codes.
3. Is using switch statements the best approach for AWS error codes?
4. While you can use a switch statement, creating a mapping table is generally more efficient and maintainable, especially as the number of error codes increases.
5. What is the purpose of errors.As in handling AWS errors?
6. The errors.As function allows you to check if an error is of a specific type, such as smithy.APIError. This is essential for accurately identifying AWS errors in Golang.
7. Why use a custom error struct like UsecaseError?
8. A custom error struct lets you format error responses in a JSON-friendly way, making it easier for client applications to parse and understand errors.
9. How can I test AWS SDK error handling code effectively?
10. Using mock errors in unit tests allows you to simulate AWS SDK errors without calling AWS directly, helping to validate how your code responds to each error type.
11. What package provides the HTTP status constants in Golang?
12. The net/http package in Golang offers constants for HTTP status codes, making it easy to assign clear, standard responses to API clients.
13. Is it possible to catch all AWS errors with a single function?
14. Yes, by using a combination of errors.As and a mapping table or switch, you can efficiently catch and handle various AWS SDK errors in a unified way.
15. Can a mapping table slow down my application?
16. A mapping table lookup is generally faster than multiple if-else or switch statements. It’s an efficient way to handle many error codes and is highly recommended for error mapping.
17. Why is it necessary to convert AWS SDK error codes to HTTP status codes?
18. Mapping AWS error codes to HTTP statuses allows your API to return standard, consistent responses, which helps client applications understand the nature of the error quickly.
19. How can I debug AWS SDK errors that don’t match any specific error code?
20. For unexpected errors, you can return a default status like 500 (Internal Server Error) and log the error details for later review using slog.Error.

Streamlined Solutions for Handling AWS SDK Error Codes

Creating a robust error-handling mechanism for AWS SDK requests in a Golang API can save significant debugging time and improve the developer experience. Through type assertions, error mappings, and custom error structures, developers can effectively transform raw AWS error responses into readable, actionable HTTP codes. This setup is particularly useful when working with authentication errors in AWS Cognito.

By integrating unit tests with mock errors, error handling becomes reliable across different error scenarios. These techniques not only enhance API quality but also ensure the API remains adaptable and maintainable as requirements grow. Implementing these strategies keeps the API responsive and ready for production use. 🛠️