Memcached module and service for Nest,
a progressive Node.js framework for building efficient and scalable server-side applications.

Installation

npm

npm install @andreafspeziale/nestjs-memcached

yarn

yarn add @andreafspeziale/nestjs-memcached

pnpm

pnpm add @andreafspeziale/nestjs-memcached

How to use?

Module

The module is Global by default.

MemcachedModule.forRoot(options)

src/core/core.module.ts

import { Module } from '@nestjs/common';
import { MemcachedModule } from '@andreafspeziale/nestjs-memcached';

@Module({
  imports: [
    MemcachedModule.forRoot({
      connections: [
        {
          host: 'localhost',
          port: 11211,
        },
      ],
      ttl: 60,
      ttr: 30,
      superjson: true,
      keyProcessor: (key) => `prefix_${key}`,
      wrapperProcessor: ({ value, ttl, ttr }) => ({
        content: value,
        ttl,
        ...(ttr ? { ttr } : {}),
        createdAt: new Date(),
      }),
      log: true,
    }),
  ],
  ....
})
export class CoreModule {}

• For localhost single connection you can omit the connections property. Alternatively connections: { locations: [{ host: 'localhost', port: 11211 }], options: { poolSize: 20 } } or simply connections: { options: { poolSize: 20 } }
• For multiple connections you can omit the port property if the server is using the default one
• ttl is the global time to live
• ttr is the global optional time to refresh
• Typically when caching a JS object like Date you will get back a string from the cache, superjson will stringify on cache sets adding metadata in order to later parse on cache gets and retrieve the initial "raw" data
• keyProcessor is the global optional key processor function which process your cache keys
• wrapperProcessor is the global optional wrapper processor function which wraps the value to be cached and adds metadata
• log enable or disable logging (LoggerService must be provided, check Extra Providers section)

MemcachedModule.forRootAsync(options)

src/core/core.module.ts

import { Module } from '@nestjs/common';
import { ConfigModule, ConfigService } from '@nestjs/config';
import { MemcachedModule } from '@andreafspeziale/nestjs-memcached';
import { Config } from './config';

@Module({
  imports: [
    ConfigModule.forRoot({
      ....
    }),
    MemcachedModule.forRootAsync({
      useFactory: (cs: ConfigService<Config, true>) => cs.get<ConfigService['memcached']>('memcached'),
      inject: [ConfigService],
    }),
  ],
  ....
})
export class CoreModule {}

Decorators

use the client and create your own service

InjectMemcachedOptions() and InjectMemcached()

src/samples/samples.service.ts

import { Injectable } from '@nestjs/common';
import {
  InjectMemcachedOptions,
  InjectMemcached,
  MemcachedClient,
  MemcachedModuleOptions,
  MemcachedClient
} from '@andreafspeziale/nestjs-memcached';

@Injectable()
export class SamplesService {
  constructor(
    @InjectMemcachedOptions()
    private readonly memcachedModuleOptions: MemcachedModuleOptions, // Showcase purposes
    @InjectMemcached() private readonly memcachedClient: MemcachedClient
  ) {}

  ....
}

Service

out of the box service with a set of features

MemcachedService

src/samples/samples.facade.ts

import { MemcachedService } from '@andreafspeziale/nestjs-memcached';
import { SampleReturnType } from './samples.interfaces'

@Injectable()
export class SamplesFacade {
  constructor(
    private readonly memcachedService: MemcachedService,
  ) {}

  async sampleMethod(): Promise<SampleReturnType> {
    const cachedItem = await this.memcachedService.get<string>('key');

    if(cachedItem === null) {
      ....
      await this.memcachedService.set<string>('key', 'value');
      ....
    }
  }
}

You can also set all the proper Processors and CachingOptions inline in order to override the global values specified during the MemcachedModule import

await this.memcachedService.set<string>('key', 'value', { ttl: 100 });

The exported MemcachedService is an opinionated wrapper around memcached trying to be unopinionated as much as possibile at the same time.

setWithMeta enables refresh-ahead cache pattern in order to let you add a logical expiration called ttr (time to refresh) to the cached data and more.

So each time you get some cached data it will contain additional properties in order to help you decide whatever business logic needs to be applied.

Health

I usually expose an /healthz controller from my microservices in order to check third parties connection.

HealthController

src/health/health.controller.ts

import { Controller, Get } from '@nestjs/common';
import {
  HealthCheckService,
  HealthCheckResult,
  HealthIndicatorResult,
  MicroserviceHealthIndicator,
} from '@nestjs/terminus';
import { Transport } from '@nestjs/microservices';
import { Config } from '../config';
import { ConfigService } from '@nestjs/config';

@Controller('healthz')
export class HealthController {
  constructor(
    private readonly health: HealthCheckService,
    private readonly microservice: MicroserviceHealthIndicator,
    private readonly cs: ConfigService<Config, true>,
  ) {}

  @Get()
  check(): Promise<HealthCheckResult> {
    return this.health.check([
      (): Promise<HealthIndicatorResult> =>
        this.microservice.pingCheck('memcached', {
          transport: Transport.TCP,
          options: {
            host: this.cs.get<Config['memcached']>('memcached').connections?.[0].host,
            port: this.cs.get<Config['memcached']>('memcached').connections?.[0].port,
          },
        }),
    ]);
  }
}

Validation

As mentioned above I usually init my DynamicModules injecting the ConfigService exposed by the ConfigModule (@nestjs/config package). This is where I validate my environment variables using a schema validator of my choice, so far I tried joi, class-validator and zod.

This is an example using joi but you should tailor it based on your needs, starting by defining a Config interface:

src/config/config.interfaces.ts

import {
  BaseWrapper,
  MemcachedConfig,
} from '@andreafspeziale/nestjs-memcached';



/**
 * Cached data shape leveraging metadata feature
 * {
 *   content: T;
 *   ttl: number;
 *   ttr?: number;
 *   version: number;
 *   created: Date;
 * }
 */
export interface CachedMetaConfig {
  version: number;
  created: Date;
}

export type Cached<T = unknown> = BaseWrapper<T> & CachedMetaConfig;

export type Config = .... & MemcachedConfig<unknown, Cached>;

src/config/config.schema.ts

import {
  MEMCACHED_HOST,
  MEMCACHED_PORT,
  MEMCACHED_TTL,
  MEMCACHED_TTR,
  MEMCACHED_VERSION
} from '@andreafspeziale/nestjs-memcached';
import {
  MEMCACHED_PREFIX
} from './config.defaults';

const BASE_SCHEMA = ....;

const MEMCACHED_SCHEMA = Joi.object({
  MEMCACHED_HOST: Joi.string().default(MEMCACHED_HOST),
  MEMCACHED_PORT: Joi.number().default(MEMCACHED_PORT),
  MEMCACHED_TTL: Joi.number().default(MEMCACHED_TTL),
  MEMCACHED_TTR: Joi.number().less(Joi.ref('MEMCACHED_TTL')).default(MEMCACHED_TTR),
  MEMCACHED_PREFIX: Joi.string().default(MEMCACHED_PREFIX),
  MEMCACHED_VERSION: Joi.number().default(MEMCACHED_VERSION),
});

export const envSchema = Joi.object()
  .concat(BASE_SCHEMA);
  .concat(MEMCACHED_SCHEMA)

src/config/index.ts

import { Config } from './config.interfaces';

export * from './config.interfaces';
export * from './config.schema';

export default (): Config => ({
  ....,
  memcached: {
    connections: [
      {
        host: process.env.MEMCACHED_HOST,
        port: parseInt(process.env.MEMCACHED_PORT, 10),
      },
    ],
    ttl: parseInt(process.env.MEMCACHED_TTL, 10),
    ...(process.env.MEMCACHED_TTR ? { ttr: parseInt(process.env.MEMCACHED_TTR, 10) } : {}),
    wrapperProcessor: ({ value, ttl, ttr }) => ({
      content: value,
      ttl,
      ...(ttr ? { ttr } : {}),
      version: parseInt(process.env.MEMCACHED_VERSION, 10),
      created: new Date(),
    }),
    keyProcessor: (key: string) =>
      `${process.env.MEMCACHED_PREFIX}::V${process.env.MEMCACHED_VERSION}::${key}`,
  },
});

src/core/core.module.ts

import { ConfigModule, ConfigService } from '@nestjs/config';
import { MemcachedModule } from '@andreafspeziale/nestjs-memcached';
import config, { envSchema, Config } from '../config';

@Module({
  imports: [
    ConfigModule.forRoot({
      isGlobal: true,
      load: [config],
      validationSchema: envSchema,
    }),
    MemcachedModule.forRootAsync({
      useFactory: (cs: ConfigService<Config, true>) => cs.get<Config['memcached']>('memcached'),
      inject: [ConfigService],
    }),
    ....
  ],
})
export class CoreModule {}

src/users/users.facade.ts

import { MemcachedService } from '@andreafspeziale/nestjs-memcached';
import { Cached } from '../config';
import { User } from './users.interfaces'

@Injectable()
export class UsersFacade {
  constructor(
    private readonly usersService: UsersService,
    private readonly memcachedService: MemcachedService
  ) {}

  async getUser(id: string): Promise<User> {
    const cachedUser = await this.memcachedService.get<Cached<User>(
      id, { superjson: true }
    );

    /**
     * Cached data shape leveraging metadata feature
     * {
     *   content: User;
     *   ttl: number;
     *   ttr?: number;
     *   version: number;
     *   created: Date;
     * }
     */

    if(cachedItem === null) {
      ....
      await this.memcachedService.setWithMeta<User, Cached<User>>(
        id, user, { superjson: true }
      );
      ....

      return user;
    }

    return cachedUser.content;
}

Extra Providers

This is one of the most recent additions.

I was looking for a nice way to introduce logging after I created and published the nestjs-log npm package.

My thoughts were:

• nestjs-log
  • can be declared as peerDependency and be installed as devDependency of consumer packages which may need logging
  • can be installed as dependency of applications which will need logging for sure
• nestjs-memcached
  • can be a nestjs-log consumer
  • can be installed as dependency of applications (or even packages, why not?) which will need caching
• application which can install both the above packages and orchestrate everything like configs and Providers DI

A visual representation can be

In terms of code, in nestjs-memcached itself:

import { Injectable, Optional } from '@nestjs/common';
import { LoggerService } from '@andreafspeziale/nestjs-log';
import {
  InjectMemcachedOptions,
  InjectMemcached,
  InjectMemcachedLogger,
} from './memcached.decorators';
....

@Injectable()
export class MemcachedService {
  ....
  constructor(
    @InjectMemcachedOptions()
    private readonly memcachedModuleOptions: MemcachedModuleOptions,
    @InjectMemcached() private readonly memcachedClient: MemcachedClient,
    @Optional()
    @InjectMemcachedLogger()
    private readonly logger?: LoggerService,
  ) {
    this.memcachedModuleOptions.log && this.logger?.setContext(MemcachedService.name);

    ....
  }
}

In your application:

src/core/core.module.ts

import { ConfigModule, ConfigService } from '@nestjs/config';
import { LoggerModule, LoggerService } from '@andreafspeziale/nestjs-log';
import { getMemcachedLoggerToken, MemcachedModule } from '@andreafspeziale/nestjs-memcached';
import config, { envSchema, Config } from '../config';

@Module({
  imports: [
    ConfigModule.forRoot({
      isGlobal: true,
      load: [config],
      validationSchema: envSchema,
    }),
    LoggerModule.forRootAsync({
      useFactory: (cs: ConfigService<Config, true>) => cs.get<Config['logger']>('logger'),
      inject: [ConfigService],
    }),
    MemcachedModule.forRootAsync({
      useFactory: (cs: ConfigService<Config, true>) => cs.get<Config['memcached']>('memcached'),
      inject: [ConfigService],
      extraProviders: [{ provide: getMemcachedLoggerToken(), useExisting: LoggerService }],
    }),
    ....
  ],
})
export class CoreModule {}

The above extraProviders option is optional and the actual logging is driven by:

• the application logger level configured within the LoggerModule
• the MemcachedModule log configuration key

Test

• docker compose -f compose-test.yaml up -d
• pnpm test

Stay in touch

• Author - Andrea Francesco Speziale
• Website - https://nestjs.com
• Twitter - @nestframework

License

nestjs-memcached MIT licensed.