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NestJS MurLock

MurLock is a distributed lock solution designed for the NestJS framework. It provides a decorator @MurLock() that allows for critical sections of your application to be locked to prevent race conditions. MurLock uses Redis to ensure locks are respected across multiple instances of your application, making it perfect for microservices.

Features

Installation

MurLock has a peer dependency on @nestjs/common and reflect-metadata. These should already be installed in your NestJS project. In addition, you'll also need to install the redis package.

npm install --save murlock redis reflect-metadata

Basic Usage

MurLock is primarily used through the @MurLock() decorator.

First, you need to import the MurLockModule and set it up in your module using forRoot. This method is used for global configuration that can be reused across different parts of your application.

import { MurLockModule } from 'murlock';

@Module({
  imports: [
    MurLockModule.forRoot({
      redisOptions: { url: 'redis://localhost:6379' },
      wait: 1000,
      maxAttempts: 3,
      logLevel: 'log',
      ignoreUnlockFail: false,
    }),
  ],
})
export class AppModule {}

Then, you can use @MurLock() in your services:

import { MurLock } from 'murlock';

@Injectable()
export class AppService {
  @MurLock(5000, 'user.id')
  async someFunction(user: User): Promise<void> {
    // Some critical section that only one request should be able to execute at a time
  }
}

By default, if there is single wrapped parameter, the property of parameter can be called directly as it shown.

import { MurLock } from 'murlock';

@Injectable()
export class AppService {
  @MurLock(5000, 'userId')
  async someFunction({ userId, firstName, lastName }: { userId: string, firstName: string, lastName: string} ): Promise<void> {
    // Some critical section that only one request should be able to execute at a time
  }
}

If there are multiple wrapped parameter, you can call it by {index of parameter}.{parameter name} as it shown

import { MurLock } from 'murlock';

@Injectable()
export class AppService {
  @MurLock(5000, '0.userId', '1.transactionId')
  async someFunction({ userId, firstName, lastName }: UserDTO, { balance, transactionId }: TransactionDTO ): Promise<void> {
    // Some critical section that only one request should be able to execute at a time
  }
}

In the example above, the @MurLock() decorator will prevent someFunction() from being executed concurrently for the same user. If another request comes in for the same user before someFunction() has finished executing, it will wait up to 5000 milliseconds (5 seconds) for the lock to be released. If the lock is not released within this time, an MurLockException will be thrown.

The parameters to @MurLock() are a release time (in milliseconds), followed by any number of key parameters. The key parameters are used to create a unique key for each lock. They should be properties of the parameters of the method. In the example above, 'user.id' is used, which means the lock key will be different for each user ID.

Advanced Usage

MurLock also supports async configuration. This can be useful if your Redis configuration is not known at compile time.

import { MurLockModule } from 'murlock';

@Module({
  imports: [
    MurLockModule.forRootAsync({
      imports: [ConfigModule],
      useFactory: async (configService: ConfigService) => ({
        redisOptions: configService.get('REDIS_OPTIONS'),
        wait: configService.get('MURLOCK_WAIT'),
        maxAttempts: configService.get('MURLOCK_MAX_ATTEMPTS'),
        logLevel: configService.get('LOG_LEVEL'),
        ignoreUnlockFail: configService.get('LOG_LEVEL')
      }),
      inject: [ConfigService],
    }),
  ],
})
export class AppModule {}

In the example above, the ConfigModule and ConfigService are used to provide the configuration for MurLock asynchronously.

For more details on usage and configuration, please refer to the API documentation below.

Using Custom Lock Key

By default, murlock use class and method name prefix for example Userservice:createUser:{userId}. By setting lockKeyPrefix as 'custom' you can define by yourself manually.

import { MurLockModule } from 'murlock';

@Module({
  imports: [
    MurLockModule.forRootAsync({
      imports: [ConfigModule],
      useFactory: async (configService: ConfigService) => ({
        redisOptions: configService.get('REDIS_OPTIONS'),
        wait: configService.get('MURLOCK_WAIT'),
        maxAttempts: configService.get('MURLOCK_MAX_ATTEMPTS'),
        logLevel: configService.get('LOG_LEVEL'),
        lockKeyPrefix: 'custom'
      }),
      inject: [ConfigService],
    }),
  ],
})
export class AppModule {}

import { MurLock } from 'murlock';

@Injectable()
export class AppService {
  @MurLock(5000, 'someCustomKey', 'userId')
  async someFunction(userId): Promise<void> {
    // Some critical section that only one request should be able to execute at a time
  }
}

Ignoring Unlock Failures

In some scenarios, throwing an exception when a lock cannot be released can be undesirable. For example, you might prefer to log the failure and continue without interrupting the flow of your application. To enable this behavior, set the ignoreUnlockFail option to true in your configuration:

import { MurLockModule } from 'murlock';

MurLockModule.forRoot({
  redisOptions: { url: 'redis://localhost:6379' },
  wait: 1000,
  maxAttempts: 3,
  logLevel: 'log',
  ignoreUnlockFail: true, // Unlock failures will be logged instead of throwing exceptions.
  lockKeyPrefix: 'default' // optional, use 'default' if you would like to lock keys as servicename:methodname:customdata, otherwise use 'custom' to manually write each lock key
}),

If we assume userId as 65782628 Lockey here will be someCustomKey:65782628

Using MurLockService Directly

While the @MurLock() decorator provides a convenient and declarative way to handle locking within your NestJS application, there may be cases where you need more control over the lock lifecycle. For such cases, MurLockService offers a programmatic way to manage locks, allowing for fine-grained control over the lock and unlock process through the runWithLock method.

Injecting MurLockService

First, inject MurLockService into your service:

import { Injectable } from '@nestjs/common';
import { MurLockService } from 'murlock';

@Injectable()
export class YourService {
  constructor(private murLockService: MurLockService) {}
  
  // Your methods where you want to use the lock
}

Acquiring a Lock

You no longer need to manually manage lock and unlock. Instead, use the runWithLock method, which handles both acquiring and releasing the lock:

async performTaskWithLock() {
  const lockKey = 'unique_lock_key';
  const lockTime = 3000; // Duration for which the lock should be held, in milliseconds

  try {
    await this.murLockService.runWithLock(lockKey, lockTime, async () => {
      // Proceed with the operation that requires the lock
    });
  } catch (error) {
    // Handle the error if the lock could not be acquired or any other exceptions
    throw error;
  }
}

Handling Errors

The runWithLock method throws an exception if the lock cannot be acquired within the specified time or if an error occurs during the execution of the function:

try {
  await this.murLockService.runWithLock(lockKey, lockTime, async () => {
    // Locked operations
  });
} catch (error) {
  // Error handling logic
}

Directly using MurLockService gives you finer control over lock management but also increases the responsibility to ensure locks are correctly managed throughout your application's lifecycle.

This refined section is suitable for developers looking for documentation on using MurLockService directly in their projects and adheres to the typical conventions found in README files for open-source projects.

Best Practices and Considerations

API Documentation

MurLock(releaseTime: number, ...keyParams: string[])

A method decorator to indicate that a particular method should be locked.

Configuration Options

Here are the customizable options for MurLockModule, allowing you to tailor its behavior to best fit your application's needs:

MurLockService

A NestJS injectable service to interact with the locking mechanism directly.

Limitations

Contributions & Support

We welcome contributions! Please see our contributing guide for more information. For support, raise an issue on our GitHub repository.

License

This project is licensed under the MIT License.

Contact

If you have any questions or feedback, feel free to contact me at ozmen.eyupfurkan@gmail.com.

We hope you find MurLock useful in your projects. Don't forget to star our repo if you find it helpful!

Happy coding! 🚀