Race detected when testing in parallel about simplebank HOT 3 CLOSED

Hey Huangbo,
The race issue is indeed caused by the validator engine being called multiple times by the parallel test cases (when they create a new server).
So the solution is to just move it out of the NewServer() function, and put it inside the special init() function:

func init() {
	if v, ok := binding.Validator.Engine().(*validator.Validate); ok {
		v.RegisterValidation("currency", validCurrency)
	}
}

// NewServer creates a new HTTP server and set up routing.
func NewServer(config util.Config, store db.Store) (*Server, error) {
	tokenMaker, err := token.NewPasetoMaker(config.TokenSymmetricKey)
	if err != nil {
		return nil, fmt.Errorf("cannot create token maker: %w", err)
	}

	server := &Server{
		config:     config,
		store:      store,
		tokenMaker: tokenMaker,
	}

	server.setupRouter()
	return server, nil
}

If you have any further questions, don't hesitate to join Tech School's discord group to discuss directly with me and other student: https://bit.ly/techschooldc

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@techschool Thanks for your reply, your solution do save me!

I understand now that register validator in init() function make sure RegisterValidation called only once.

But I'm still confused why the sync.Mutex not working.
According to the RegisterValidation doc, it say "if the key already exists, the previous validation function will be replaced.", I think it should works well, even if it's inefficient. Am I use the mutex in a wrong way?

Here the way I use mutex:

var mutex sync.Mutex

// NewServer creates a new HTTP server and setup routing
func NewServer(config util.Config, store db.Store) (*Server, error) {
	tokenMaker, err := token.NewPasetoMaker(config.TokenSymmetricKey)
	if err != nil {
		return nil, fmt.Errorf("cannot create token make: %w", err)
	}
	server := &Server{
		config:     config,
		store:      store,
		tokenMaker: tokenMaker,
	}
	
	mutex.Lock()
	if v, ok := binding.Validator.Engine().(*validator.Validate); ok {
		err := v.RegisterValidation("currency", validCurrency)
		if err != nil {
			log.Fatal("register validation err:", err)
		}
	}
	mutex.Unlock()
	
	server.setupRouter()

	return server, nil
}

Sorry to bother again.

from simplebank.

@techschool Thanks for your reply, your solution do save me!

I understand now that register validator in init() function make sure RegisterValidation called only once.

But I'm still confused why the sync.Mutex not working. According to the RegisterValidation doc, it say "if the key already exists, the previous validation function will be replaced.", I think it should works well, even if it's inefficient. Am I use the mutex in a wrong way?

Here the way I use mutex:

var mutex sync.Mutex

// NewServer creates a new HTTP server and setup routing
func NewServer(config util.Config, store db.Store) (*Server, error) {
	tokenMaker, err := token.NewPasetoMaker(config.TokenSymmetricKey)
	if err != nil {
		return nil, fmt.Errorf("cannot create token make: %w", err)
	}
	server := &Server{
		config:     config,
		store:      store,
		tokenMaker: tokenMaker,
	}
	
	mutex.Lock()
	if v, ok := binding.Validator.Engine().(*validator.Validate); ok {
		err := v.RegisterValidation("currency", validCurrency)
		if err != nil {
			log.Fatal("register validation err:", err)
		}
	}
	mutex.Unlock()
	
	server.setupRouter()

	return server, nil
}

Sorry to bother again.

The mutexes are not working because each test runs in its own goroutine when you use t.Parallel().
Each test gets its own instance of the mutex, so the mutex doesn't prevent the concurrent execution of the tests which leads to race conditions where multiple tests try to acquire the lock at the same time.
so even if you declare a mutex outside the function, each test will have its own instance of the mutex. Quang's solution is the way to go i guess.

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