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

- Redis-Based: Implements a fast and effective lock mechanism using Redis.
- Parameter-Based Locking: Creates locks based on request parameters or bodies.
- Highly Customizable: Customize many parameters, such as lock duration.
- Retry Mechanism: Implements an exponential back-off strategy if the lock is not obtained.
- Logging: Provides logging options for debugging and monitoring.
- OOP and Generic Structure: Easily integratable and expandable due to its OOP and generic design.
- Blocking Mode: Optional infinite retry mode for critical operations.
- Robust Redis Connection: Automatic reconnection with configurable strategy.
- Fail-Fast Option: Configurable behavior on Redis connection failures.

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.

``bash
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.

`typescript
import { MurLockModule } from 'murlock';

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

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

`typescript
import { MurLock } from 'murlock';

@Injectable()
export class AppService {
@MurLock(5000, 'user.id')
async someFunction(user: User): Promise {
// 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.

`typescript
import { MurLock } from 'murlock';

@Injectable()
export class AppService {
@MurLock(5000, 'userId')
async someFunction({
userId,
firstName,
lastName,
}: {
userId: string;
firstName: string;
lastName: string;
}): Promise {
// 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

`typescript
import { MurLock } from 'murlock';

@Injectable()
export class AppService {
@MurLock(5000, '0.userId', '1.transactionId')
async someFunction(
{ userId, firstName, lastName }: UserDTO,
{ balance, transactionId }: TransactionDTO
): Promise {
// 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.

`typescript
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('IGNORE_UNLOCK_FAIL'),
failFastOnRedisError: configService.get('FAIL_FAST_ON_REDIS_ERROR'),
blocking: configService.get('BLOCKING_MODE'),
}),
inject: [ConfigService],
}),
],
})
export class AppModule {}
`

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

Overriding Global Wait Per Decorator

You can override the global wait parameter per decorator, allowing fine-grained retry control:

$3

`typescript
@MurLock(
5000,
(retries) => (Math.floor(Math.random() 50) + 50) retries,
'user.id',
)
async someFunction(user: User): Promise {
// This uses a randomized backoff strategy for retrying lock acquisition.
}
`

$3

`typescript
@MurLock(5000, 1500, 'user.id')
async anotherFunction(user: User): Promise {
// This will retry every 1500ms instead of global wait.
}
`

- If no wait is provided in decorator, MurLock will fallback to global wait from forRoot().
- Allows dynamic retry logic per critical section.

Decorator Composition

When using @MurLock with other decorators (such as @Transactional from typeorm-transactional), you may encounter issues with parameter name extraction if the other decorator wraps the method before @MurLock is applied.

$3

TypeScript decorators execute in bottom-up order. If another decorator wraps the method before @MurLock, the parameter names cannot be extracted from the wrapped function:

`typescript
// This may fail if @Transactional wraps the method before @MurLock executes
@MurLock(5000, 'userData.id')
@Transactional()
async process(userData: { id: string }, options: string[] = []): Promise {
// Error: Parameter userData not found in method arguments
}
`

$3

Use the SetParamNames decorator to explicitly specify parameter names. Important: SetParamNames must be placed below @MurLock in the code (it will execute before @MurLock due to TypeScript's bottom-up decorator execution order).

#### Option 1: Object Format (Recommended)

The object format allows you to specify only the parameters you need, with explicit index mapping. This provides O(1) lookup performance and doesn't require specifying all parameters:

`typescript
import { MurLock, SetParamNames } from 'murlock';

class MyService {
@MurLock(5000, 'userData.id')
@SetParamNames({ userData: 0 }) // Only specify needed params with their indices
@Transactional()
async process(
userData: { id: string },
options: string[],
context: any
): Promise {
// This will work correctly - only userData is needed for the lock key
}
}
`

Benefits of Object Format:

- Partial specification: Only specify the parameters you actually use in the lock key
- Order independent: Parameter indices are explicit, so declaration order doesn't matter
- O(1) lookup: Direct property access instead of array indexOf search
- Self-documenting: The index mapping clearly shows which argument position each name refers to

`typescript
// Example: Only need the third parameter for the lock key
@MurLock(5000, 'context.tenantId')
@SetParamNames({ context: 2 }) // context is at index 2
@Transactional()
async process(userData: any, options: any, context: { tenantId: string }): Promise {
// ...
}
`

#### Option 2: Array Format (Legacy)

The array format requires specifying ALL parameters in order:

`typescript
import { MurLock, SetParamNames } from 'murlock';

class MyService {
@MurLock(5000, 'userData.id')
@SetParamNames('userData', 'options') // Must specify ALL params in order
@Transactional()
async process(
userData: { id: string },
options: string[] = []
): Promise {
// This will work correctly
}
}
`

> Note: The array format uses indexOf to find parameters, so all parameters must be specified in the correct order. If you only need one parameter, the object format is recommended.

Decorator Execution Order (bottom-up):

1. @Transactional() executes first and wraps the method
2. @SetParamNames executes second and stores parameter names in metadata
3. @MurLock executes last and reads parameter names from metadata

If you place @SetParamNames above @MurLock, it will execute after @MurLock, and the metadata won't be available when @MurLock needs it.

$3

As a workaround, you can use parameter indices instead of names:

`typescript
@MurLock(5000, '0.id') // Uses index 0 for userData
@Transactional()
async process(userData: { id: string }, options: string[] = []): Promise {
// This works, but name-based keys are more readable
}
`

$3

- SetParamNames stores parameter names in metadata before the method is wrapped
- @MurLock reads the parameter names from metadata when the function is already wrapped
- This allows decorator composition to work correctly regardless of execution order

Blocking Mode

MurLock supports a blocking mode where it will continuously retry to acquire the lock until successful. This is useful for critical operations that must eventually succeed.

`typescript
@Module({
imports: [
MurLockModule.forRoot({
redisOptions: { url: 'redis://localhost:6379' },
wait: 1000,
maxAttempts: 3,
logLevel: 'log',
blocking: true, // Enable blocking mode
}),
],
})
export class AppModule {}
`

When blocking mode is enabled:

- The maxAttempts parameter is ignored
- The service will continuously retry to acquire the lock
- Each retry will wait for the specified wait time
- Redis errors will be logged but won't stop the retry process

Redis Connection Handling

MurLock includes robust Redis connection handling:

- Automatic Reconnection: Implements a reconnection strategy with exponential backoff
- Connection Events: Logs connection status changes (ready, reconnecting, end)
- Fail-Fast Option: Can be configured to exit the application on Redis connection failures

`typescript
@Module({
imports: [
MurLockModule.forRoot({
redisOptions: {
url: 'redis://localhost:6379',
socket: {
keepAlive: false,
reconnectStrategy: (retries) => {
const delay = Math.min(retries * 500, 5000);
return delay;
},
},
},
failFastOnRedisError: true, // Exit application on Redis connection failure
}),
],
})
export class AppModule {}
`

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.

`typescript
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 {}
`

`typescript
import { MurLock } from 'murlock';

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

$3

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:

`typescript
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.

$3

First, inject MurLockService into your service:

`typescript
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:

`typescript
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;
}
}
`

$3

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:

`typescript
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.

Best Practices and Considerations

- Short-lived Locks: Ensure that locks are short-lived to prevent deadlocks and to increase the efficiency of your application.
- Error Handling: Robustly handle errors during lock acquisition:
- Graceful Failures: If a lock cannot be obtained, handle the situation gracefully, potentially logging the incident and retrying the operation.
- Consider Failures in Unlocking: Even with ignoreUnlockFail set to true, implement error handling strategies to log and manage unlock failures, ensuring they do not disrupt the application flow.
- Logging: Adjust the logLevel based on your environment. Use 'debug' for development and 'error' or 'warn' for production.
- Consistency: Use consistent lock keys that clearly represent the resources or operations they are meant to protect.
- Customizable Lock Keys: Utilize the lockKeyPrefix to tailor how lock keys are constructed:
- Default: Automatically includes the class and method name, e.g., Userservice:createUser:{userId}.
- Custom: Set lockKeyPrefix to 'custom' and define lock keys explicitly to fine-tune lock scope and granularity.
- Resource Cleanup: Even though runWithLock manages lock cleanup, ensure your application logic correctly handles any necessary cleanup or rollback in case of errors.
- Use of Finally Block: Explicitly manage lock release in a finally block to ensure that locks are always released, preventing potential deadlocks and resource leaks.
- Redis Connection: Configure Redis connection options appropriately for your environment:
- Use failFastOnRedisError in production to ensure application fails fast on Redis connection issues
- Consider using blocking mode for critical operations that must eventually succeed
- Configure appropriate reconnection strategies based on your network reliability

API Documentation

$3

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

- releaseTime: Time in milliseconds after which the lock should be automatically released.
- wait (optional): Time in milliseconds to wait between retry attempts, or a function that calculates wait time based on retry count.
- ...keyParams: Method parameters based on which the lock should be made. The format is paramName.attribute. If just paramName is provided, it will use the toString method of that parameter.

$3

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

- redisOptions: Configuration settings for the Redis client, such as the connection URL and socket options.
- wait: Time in milliseconds to wait before retrying to obtain a lock if the initial attempt fails.
- maxAttempts: The maximum number of attempts to try and acquire a lock before giving up (ignored in blocking mode).
- logLevel: Determines the level of logging used within the module. Options include 'none', 'error', 'warn', 'log', or 'debug'.
- ignoreUnlockFail (optional): When set to true, the module will not throw an exception if releasing a lock fails. This setting helps in scenarios where failing silently is preferred over interrupting the application flow. Defaults to false to ensure that failures are noticed and handled appropriately.
- lockKeyPrefix (optional): Specifies how lock keys are prefixed, allowing for greater flexibility:
- Default: Uses class and method names as prefixes, e.g., Userservice:createUser:{userId}.
- Custom: Set this to 'custom' to define lock keys manually in your service methods, allowing for specific lock key constructions beyond the standard naming.
- failFastOnRedisError (optional): When set to true, the application will exit with code 1 if a Redis connection error occurs. Defaults to false.
- blocking (optional): When set to true, the lock acquisition will retry indefinitely until successful. Defaults to false`.

$3

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

Limitations

- Redis Persistence: Ensure that your Redis instance has RDB persistence enabled. This ensures that in case of a crash, locks are not lost.
- Single Redis Instance: MurLock is not designed to work with Redis cluster mode. It's essential to ensure that locks are always set to a single instance.

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 .

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

Happy coding! 🚀