GetMutex: Bulletproof Concurrency for Dart

🔒 GetMutex is your solution for robust, efficient, and deadlock-free synchronization in Dart. Concurrency made simple, without sacrificing performance.

Why GetMutex?

In the world of concurrent programming, race conditions can wreak havoc on your code, leading to unpredictable outcomes. GetMutex is here to eliminate those risks while offering:

• 🚀 High Performance: Outperforms naive await-based solutions by up to 2x in our benchmarks.
• 🛡️ Reliable Protection: Locks down your critical sections with precision, ensuring data integrity.
• 🧠 Simple API: User-friendly, intuitive API that makes concurrency less daunting.
• 🔬 100% Test Coverage: We take your data's safety seriously, and it shows.

Let’s dive into a real-world example to illustrate why GetMutex is indispensable.

The Bank Account Problem: A Case of Concurrent Chaos

Imagine you're building a banking app. Without proper synchronization, concurrent transfers can lead to financial discrepancies. Here’s what happens without GetMutex:

Without Synchronization (Prone to Race Conditions)

Imagine you're building a banking app. Without proper synchronization, you're one concurrent transfer away from a financial disaster. Let's see what happens without GetMutex:

import 'dart:async';

class BankAccount {
  final String accountNumber;
  double balance;

  BankAccount(this.accountNumber, this.balance);

  Future<bool> transfer(BankAccount targetAccount, double amount) async {
    if (amount > balance) {
      return false; // Insufficient funds
    }

    await Future.delayed(Duration(milliseconds: 50)); // Simulating processing time

    balance -= amount;

    await Future.delayed(Duration(milliseconds: 50)); // Simulate some delay

    targetAccount.balance += amount;

    return true;
  }
}

void main() async {
  final accountA = BankAccount('Account A', 1000);
  final accountB = BankAccount('Account B', 500);

  // Simulate multiple concurrent transfers
  final transfers = [
    accountA.transfer(accountB, 200), // Account A: $800, Account B: $700
    accountA.transfer(accountB, 300), // Account A: $500, Account B: $1000
    accountB.transfer(accountA, 100), // Account A: $600, Account B: $900
    accountB.transfer(accountA, 700), // Account A: $1300, Account B: $200
  ];

  final results = await Future.wait(transfers);

  print('Transfer Results:');
  for (var result in results) {
    print(result ? 'Transfer succeeded' : 'Transfer failed');
  }
  // Possible Output:
  // Transfer succeeded
  // Transfer succeeded
  // Transfer succeeded
  // Transfer failed

  print('Final Balances:');
  print('${accountA.accountNumber}: \$${accountA.balance}');
  print('${accountB.accountNumber}: \$${accountB.balance}');
  // Possible Output:
  // Account A: $600.0
  // Account B: $900.0
}

The Problem

You might expect the final balances to be:

• Account A: $1300.0
• Account B: $200.0

But due to race conditions, you could end up with:

• Account A: $600.0
• Account B: $900.0

Money has been created out of thin air! 💸 This is because multiple transfers are happening concurrently without proper synchronization.

The "Await" Solution (Spoiler: It's Slow)

You might think, "I'll just use await before each operation!" Sure, it works, but at what cost?

void main() async {
  final accountA = BankAccount('Account A', 1000);
  final accountB = BankAccount('Account B', 500);

  final clockWatch = Stopwatch()..start();
  await accountA.transfer(accountB, 200);
  await accountA.transfer(accountB, 300);
  await accountB.transfer(accountA, 100);
  await accountB.transfer(accountA, 700);
  clockWatch.stop();
  print('Elapsed time using await: ${clockWatch.elapsedMilliseconds} ms');
  // Output: Elapsed time using await: 209 ms
}

Enter GetMutex: Safe and Swift

Now, let's see how GetMutex handles this with grace and speed:

import 'package:get_mutex/get_mutex.dart';

class BankAccount {
  final String accountNumber;
  double balance;
  final mutex = Mutex();

  BankAccount(this.accountNumber, this.balance);

  Future<bool> transfer(BankAccount targetAccount, double amount) async {
    return await mutex.protectWrite(() async {
      if (amount > balance) return false;
      balance -= amount;
      await targetAccount.deposit(amount);
      return true;
    });
  }

  Future<void> deposit(double amount) async => balance += amount;
}

void main() async {
  final accountA = BankAccount('Account A', 1000);
  final accountB = BankAccount('Account B', 500);

  final transfers = [
    accountA.transfer(accountB, 200),
    accountA.transfer(accountB, 300),
    accountB.transfer(accountA, 100),
    accountB.transfer(accountA, 700),
  ];

  final clockWatch = Stopwatch()..start();
  await Future.wait(transfers);
  clockWatch.stop();
  print('Elapsed time using mutex: ${clockWatch.elapsedMilliseconds} ms');
  // Output: Elapsed time using mutex: 107 ms

  print('Final Balances:');
  print('${accountA.accountNumber}: \$${accountA.balance}'); // Account A: $1300.0
  print('${accountB.accountNumber}: \$${accountB.balance}'); // Account B: $200.0
}

With GetMutex, not only are your accounts safe and your transfers atomic, but you're also doing it in half the time! 🚀

Features That'll Make You Smile

• 🔄 Simple and Reentrant Mutexes: Lock it once, lock it twice, we've got you covered.
• 📚 Read-Write Locks: Because sometimes, sharing is caring (and performant).
• ⏱️ Timeouts and Cancellation: Because even mutexes shouldn't wait forever.
• 🎛️ Flexible Policies: Fair, readers-first, or writers-first – you're in control.

Getting Started

1. Add GetMutex to your pubspec.yaml:

   dependencies:
     get_mutex: ^1.0.0
   

2. Run: dart pub get

3. Import and enjoy:

   import 'package:get_mutex/get_mutex.dart';
   
   final mutex = Mutex();
   await mutex.protectWrite(() {
     // Your critical section here
     print('Writing safely!');
   });
   

Advanced Usage

GetMutex grows with your needs. Need more control? We've got you covered:

final mutex = Mutex();

// Optimize for multiple readers
await mutex.protectRead(() => print('Reading in parallel'));

// Ensure exclusive access for writers
await mutex.protectWrite(() => print('Writing exclusively'));

// Set a timeout to avoid deadlocks
await mutex.protectWrite(() => longOperation(), timeout: Duration(seconds: 5));

// Use cancellation for more control
final token = CancellationToken();
await mutex.protectWrite(() => cancelableOperation(), cancellationToken: token);

We also support raw read-write locks for fine-grained control over your shared resources, but with the same ease of use (however, we recommend using Mutex for most cases, RawReadWriteMutex is more low-level, and HAVE NO SUPPORT for reentrant locks):

final rwMutex = RawReadWriteMutex();

await rwMutex.protectRead(() => print('Reading in parallel'));
await rwMutex.protectWrite(() => print('Writing exclusively'));


Future<T> myCustomProtectWrite<T>(
    Future<T> Function() action, {
    CancellationToken? cancellationToken,
    Duration? timeout,
  }) async {
    await rwMutex.acquireWrite(cancellationToken: cancellationToken, timeout: timeout);
    try {
      return await action();
    } finally {
      rwMutex.releaseWrite();
    }
}

Do you want keep it simple? We have a SimpleMutex/SimpleReentrantMutex for you:

final simpleMutex = SimpleMutex();
await simpleMutex.protect(() => print('Simple Mutex'));

final simpleReentrantMutex = SimpleReentrantMutex();
await simpleReentrantMutex.protect(() {
  print('Simple Reentrant Mutex');
  simpleReentrantMutex.protect(() => print('Reentrant Mutex inside'));
});

For sake of simplicity, we have an alias GetMutex class that has all available mutexes:

final mutex = GetMutex.mutex();
await mutex.protectWrite(() => print('Writing safely!'));

final rwMutex = GetMutex.rawReadWriteMutex();
await rwMutex.protectRead(() => print('Reading in parallel'));

final simpleMutex = GetMutex.simpleMutex();
await simpleMutex.protect(() => print('Simple Mutex'));

final simpleReentrantMutex = GetMutex.simpleReentrantMutex();
await simpleReentrantMutex.protect(() {
  print('Simple Reentrant Mutex');
  simpleReentrantMutex.protect(() => print('Reentrant Mutex inside'));
});

• 🐛 Found a bug? Open an issue.
• 💡 Have an idea? Submit a pull request.
• 🤔 Questions? Start a discussion.

License

GetMutex is released under the MIT License. See the LICENSE file for details.

Libraries

get_mutex