Technical Test DOT - gateway-service

Project Structure

technical-test-DOT/
│
├── docker-compose.yml
├── readme.md
│
├── gateway-service/
│   ├── Dockerfile
│   ├── .env
│   ├── go.mod
│   ├── readme.md  <-- This File Should be here
│   └── (other source files)
│
└── user-service/
    ├── Dockerfile
    ├── .env
    ├── go.mod
    ├── readme.md
    └── (other source files)

How to Run

To start the services, navigate to the project directory and run the following command:

cd path/to/technical-test-DOT
docker-compose up --build -d

To run the services without rebuilding:

docker-compose up -d

To rebuild the services:

docker-compose up --build

Project Overview

This project utilizes Golang as its main programming language, structured around a microservices architecture using gRPC, which is 7-10 times faster than traditional REST APIs. The entire setup runs within a Docker environment.

Key Features

1. API Endpoints: The project supports various HTTP methods including GET, POST, PUT, PATCH, and DELETE.

2. Database Interaction: The application uses GORM for ORM, with functionality to save data from APIs into a database. There is one relational connection between two tables, and the data-saving process includes transactions for consistency.

3. Centralized Error Handling: Custom error types and middleware are implemented for consistent error responses.

4. Caching: Implemented using Redis to enhance performance by caching user details.

5. API Testing: A Postman collection and environment are available for testing purposes.

API Endpoints

GET Method

• List Users: {{host}}/user/list?page=1&page_size=5
• User Details: {{host}}/user/detail?id=1
• User Activity: {{host}}/user/activity?id=1

POST Method

• Create User: {{host}}/user/create

  {
      "username": "panca",
      "full_name": "panca",
      "password": "password"
  }

PUT Method

• Update User: {{host}}/user/update?id=1

  {
      "username": "pan",
      "full_name": "pancaUpdated",
      "password": "password"
  }

PATCH Method

• Patch User: {{host}}/user/patch?id=111

  {
      "username": "pan",
      "full_name": "pancaUpdated",
      "password": "password"
  }

DELETE Method

• Delete User: {{host}}/user/delete?id=4

Detailed Implementation

Database Operations

• Transactional Handling: The Handler method in CreateUser action uses a GORM transaction to save both User and NewTable entities. If any operation within the transaction fails, the entire transaction is rolled back, ensuring data consistency.

  func (a *CreateUser) Handler(ctx context.Context, user *entity.User, newTable *entity.NewTable) error {
      return a.repoUser.DB.Transaction(func(tx *gorm.DB) error {
          if err := tx.Create(user).Error; err != nil {
              return err
          }
          newTable.UserID = user.ID
          if err := tx.Create(newTable).Error; err != nil {
              return err
          }
          return nil
      })
  }

• Relational Data: The NewTable entity has a foreign key (UserID) that references the User entity, establishing a one-to-many relationship.

Error Handling (Centered Error Handling)

• Custom Error Types: Defined in gateway-service/util/errors/error.go

  func Wrap(err error, code codes.Code, message string) *AppError {
      return &AppError{
          Code:    code,
          Message: message,
          Err:     err,
      }
  }
  
  func ErrNotFound(model string) error {
      return &AppError{
          Code:    codes.NotFound,
          Message: fmt.Sprintf("%s not found", model),
      }
  }
  
  func ErrBadRequest(msg string) error {
      return &AppError{
          Code:    codes.InvalidArgument,
          Message: msg,
      }
  }

• Middleware for Error Handling: Implemented in gateway-service/middleware/error_handler.go

  func ErrorHandlerMiddleware(next echo.HandlerFunc) echo.HandlerFunc {
      return func(c echo.Context) error {
          err := next(c)
          if err != nil {
              appErr, ok := err.(*errors.AppError)
              if ok {
                  return c.JSON(int(appErr.Code), map[string]string{"error": appErr.Message})
              }
              return c.JSON(http.StatusInternalServerError, map[string]string{"error": "internal server error"})
          }
          return nil
      }
  }

Caching with Redis

Example usage in user-service/repo/user.go:

func SaveUserToCache(ctx context.Context, redisClient *redis.Client, userDetail *entity.User) error {
    cacheKey := "user_detail_" + string(userDetail.ID)
    userData, err := json.Marshal(userDetail)
    if err != nil {
        return err
    }

    err = redisClient.Set(ctx, cacheKey, userData, 5*time.Minute).Err()
    if err != nil {
        return err
    }

    return nil
}

Testing

• API Testing: You can use the provided Postman collection and environment files located in the project directory to test the API endpoints.

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