singularity

singularity 🔎

用户问题

supertokens.goFilecheck for race conditions No locking when checking email existence and creating users Concurrent signups with same email could create duplicate users

回答

You’re right to be concerned. Your SignUp and thirdPartySignInUp flows do not prevent race conditions during concurrent signups with the same email. Here’s what’s happening and why it’s unsafe:

🔍 Core Issue

Both emailpassword.SignUp and thirdparty.SignInUp:

• Check for existing users before creating one.
• But this check is not synchronized, so two concurrent requests can pass the check, and each can attempt to create a user.

This creates a classic TOCTOU race condition (Time-of-Check to Time-of-Use).

⚠️ Race Risk in Your Flow

In SignUp:

signUpResponse, err := originalSignUp(email, password, tenantId, userContext)
// ... then check if EmailAlreadyExistsError != nil

Problem: If two concurrent requests hit here, both can proceed and emailpassword might allow both to create.

In thirdPartySignInUp:

existingUsers, err := thirdparty.GetUsersByEmail(tenantId, email)
// if len(existingUsers) == 0 → allow signup

Problem: If the same email signs up simultaneously via different providers (or even same one), both pass the check and create duplicate accounts.

🛡️ Recommended Fixes

✅ Use a DB-level unique constraint

Ensure your members table (and SuperTokens DB) has a unique index on email. You likely already have this, but it needs to surface as an error.

✅ Add explicit locking

Use a mutex or DB row-level locking (e.g., SELECT ... FOR UPDATE) around the email check + creation. Options:

1. App-level lock using a named mutex map (e.g., sync.Map[email]string -> sync.Mutex) — quick but can have perf limits under high load.
2. Redis-based distributed lock around email (recommended for scale).
3. Use ent’s transaction to wrap member creation and ensure rollback if duplicate:

tx, err := client.Tx(ctx)
defer tx.Rollback()
// check + create
tx.Commit()

✅ Harden SuperTokens override

Wrap your originalSignUp and originalSignInUp calls with your own duplicate detection:

• Catch specific constraint errors from SuperTokens (e.g., email already exists) and map them to your own error.
• Do not rely solely on EmailAlreadyExistsError — it’s not reliable under race.

🧪 Simulate and Test

Add tests that simulate 5+ concurrent signup requests with the same email. Assert:

• Only one user gets created.
• The others fail with a consistent, friendly error.

TL;DR Fix Plan

• Add mutex/lock around all signup paths.
• Add transaction + rollback for member creation.
• Ensure DB-level unique constraint on email.
• Harden error handling in overrides.
• Write concurrent tests for robustness.

Let me know if you want help wiring a mutex-based or Redis lock for this.

用户问题

i’m already using entgo transactions, show me mutex use

回答

Since you’re already using Ent’s transaction, you can use an app-level mutex map keyed by email to serialize concurrent signups for the same email. Here’s how:

✅ Step-by-step: Mutex Guard by Email

1. Add global map of mutexes (with cleanup)

var signupLocks sync.Map // map[string]*sync.Mutex

2. Lock per email

func acquireSignupLock(email string) *sync.Mutex {
    muIface, _ := signupLocks.LoadOrStore(email, &sync.Mutex{})
    mu := muIface.(*sync.Mutex)
    mu.Lock()
    return mu
}

func releaseSignupLock(email string, mu *sync.Mutex) {
    mu.Unlock()
    // Optional: cleanup to avoid leak
    signupLocks.Delete(email)
}

3. Wrap your SignUp handler

In your override (inside the wrapped SignUp or thirdPartySignInUp), do:

lock := acquireSignupLock(email)
defer releaseSignupLock(email, lock)

// now perform the original sign-up logic
signUpResponse, err := originalSignUp(email, password, tenantId, userContext)
// ...

⚠️ Gotchas

• This only serializes within a single app instance. If you run multiple instances (e.g., Kubernetes), use a Redis lock (see below).
• If SignUp panics or times out, the mutex may be leaked unless cleanup is bulletproof.

Optional: Redis Lock (for multi-node)

Use go-redsync or similar:

import "github.com/go-redsync/redsync/v4"

// Acquire lock for `email@example.com`
mutex := redsync.NewMutex("signup:" + email)
// mutex.LockContext(ctx)
// ... signup ...
// mutex.Unlock()

This scales better and avoids per-node duplication or memory growth.

Summary

If you’re single-instance or early-stage:

lock := acquireSignupLock(email)
defer releaseSignupLock(email, lock)
// Proceed with signup

If you’re production-grade, multi-instance:

• Use Redis lock instead.

Need help swapping in a Redis-backed lock? I can wire that too.

用户问题

go import sync

回答

Add this import to your Go file:

import "sync"

You’ll need it for sync.Map and sync.Mutex. Place it alongside your existing imports.

用户问题

supertokens.goFilelooks good now?

回答

Your updated file does not yet include mutex locking logic. There’s no sync.Map, sync.Mutex, or any locking mechanism visible in supertokens.go. The race condition is still present.

✅ To finalize the fix, you need to:

1. Add imports

At the top:

import (
	"sync"
	// other imports...
)

2. Add the global mutex map

var signupLocks sync.Map

3. Add helper functions

func acquireSignupLock(email string) *sync.Mutex {
	muIface, _ := signupLocks.LoadOrStore(email, &sync.Mutex{})
	mu := muIface.(*sync.Mutex)
	mu.Lock()
	return mu
}

func releaseSignupLock(email string, mu *sync.Mutex) {
	mu.Unlock()
	signupLocks.Delete(email) // optional cleanup
}

4. Wrap the SignUp override

Inside your (*originalImplementation.SignUp) override:

lock := acquireSignupLock(email)
defer releaseSignupLock(email, lock)

Just before:

signUpResponse, err := originalSignUp(email, password, tenantId, userContext)

⚠️ You also need to do the same for thirdPartySignInUp

At the top of thirdPartySignInUp:

lock := acquireSignupLock(email)
defer releaseSignupLock(email, lock)

Once you add those pieces, the signup flow will be correctly serialized per email address — preventing concurrent duplicate signups.

Would you like me to generate the exact diff for the patch?

用户问题

supertokens.goFilethis is the updated file

回答

Yes — now it looks solid. Here’s a precise breakdown:

✅ Confirmed Additions

• You’ve declared a global:

var signupLocks sync.Map

• Defined locking helpers:

func acquireSignupLock(email string) *sync.Mutex
func releaseSignupLock(email string, mu *sync.Mutex)

• You’ve wrapped SignUp logic with:

lock := acquireSignupLock(email)
defer releaseSignupLock(email, lock)

This correctly serializes concurrent signups by email within this process.

🟡 One Missing Lock (Optional but recommended)

Your custom thirdPartySignInUp(...) does not currently acquire a lock. Race can still happen there:

func thirdPartySignInUp(...) {
	// Add this:
	lock := acquireSignupLock(email)
	defer releaseSignupLock(email, lock)

	// rest of the logic...
}

This ensures you also prevent concurrent third-party signups for the same email.

✅ DB Constraint

Still make sure your members table enforces a unique index on email, to catch anything leaking past the mutex (e.g. multi-instance race).

✅ Summary

Path	Lock Added?	Comment
Email/password SignUp	✅	Safe
Third-party SignUp	❌	Add acquireSignupLock()
DB-level uniqueness	🟡	Verify it’s enforced

Once you patch the third-party path, you’re race-safe.

Let me know if you want to test with goroutines or simulate a burst scenario.

用户问题

whats the idea behind using context like this ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second) defer cancel()

回答

That pattern is used to enforce a timeout on long-running operations. Here’s what each part is doing:

🔧 Code Breakdown

ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
defer cancel()

1. context.WithTimeout(...):

• Creates a new context.Context that automatically cancels after 30 seconds.
• Useful to prevent hangs, deadlocks, or runaway queries.
  1. context.Background():
• A base context — typically used at the top level (e.g., main, HTTP handler).
  1. defer cancel():
• Ensures that resources associated with the context (timers, etc.) are released, even if timeout doesn’t occur.
• Prevents memory leaks.

🧠 Why Use It?

• To bound the execution time of DB queries, HTTP requests, etc.
• Avoids goroutines lingering forever on network errors or locks.
• Signals downstream code to stop working on something that’s no longer needed.

🟡 Without cancel()?

The context would still time out after 30s, but you’d leak the timer until garbage collection. On high load, that becomes a problem.

💡 Example Use Case

ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
defer cancel()

err := dbClient.Query().Where(...).Exec(ctx)

If the query hangs, it gets force-canceled after 5 seconds. Cleaner, safer, faster failover.

Let me know if you want a context.WithTimeout helper for your Ent operations.