NestJSRxJSLockModule

NestJS RxJS implementation of distributed lock for NestJS using Redlock

TODO

• [] Add module tests
• [] Remove nestjs-redis dependency, use ioredis directly
• [] Add lock$ docs usage example

Installation

Add @rnw-community/nestjs-rxjs-lock to your project using you package manager of choice.

Configuration

We need to create own LockModule to "wrap" typed module and service returned from the NestJSRxJSLockModule.registerTypedAsync(), this will allow us to use typesafe LockCodesEnum in our business logic.

// eslint-disable-next-line max-classes-per-file
import { Injectable, Module } from '@nestjs/common';

import { NestJSRxJSLockModule } from '@rnw-community/nestjs-rxjs-lock';
import { LockCodesEnum } from '@seezona/admin-api-backend/src/generic/enum/lock-codes.enum';

// Create a enum which would be typesafe to use in your locks
enum LockCodesEnum {
    DB_USER_CREATE = 'DB_USER_CREATE',
}

const [BaseLockModule, BaseLockService] = NestJSRxJSLockModule.registerTypedAsync<LockCodesEnum>({
    retryCount: 3,
    defaultExpireMs: 5000,
});

@Injectable()
export class LockService extends BaseLockService {}

@Module({
    imports: [BaseLockModule],
    providers: [LockService],
    exports: [LockService],
})
export class LockModule {}

Methods

NestJSRxJSLockModule.registerTypedAsync

• options is a NestJSRxJSLockModuleOptions which extends Redlock.Options object with default values):
  • retryCount is a number of lock attempts
  • defaultExpireMs is a default lock expiration time in milliseconds

Example(see Setup section for more details

NestJSRxJSService.lock$

Arguments

• name - unique lock identifier like user id in our setup example
• prefix - typesafe LockCodesEnum value from the setup, used as a prefix for the lock key
• handler$ - business logic wrapped in RxJS observable
• expireMs - lock expiration time in milliseconds, a module configuration default value is used if not provided

Redis lock key will be formed as lock:[prefix]:[name] and will be expired after expireMs milliseconds and wil retry retryCount times.

Usage

@Injectable()
export class MyUserService {
    constructor(private readonly lock: LockService /*...other dependencies...*/) {}

    createUserInDb$(user): Observable<User> {
        // business logic
    }

    createUser$(user: User): Observable<User> {
        return this.lock.lock$(user.id, LockCodesEnum.DB_USER_CREATE, () => this.createUserInDb$(user));
    }
}

lock$ method will throw an error if lock is not acquired

License

This library is licensed under The MIT License.