#8 Caching with Nestjs, Graphql and Redis

23 Aug, 2023

Even though our application does not seem to need caching at the moment, I have wanted to figure out how caching works with Nestjs and Graphql. So, we will practice caching in our application.

In Nestjs, it is easy to cache by using cache-manager. Let's begin with how to configure caching

Configrue cache using Redis

We will first install dependencies.

pnpm install @nestjs/cache-manager cache-manager

Instead of using in-memory cache by default, I have chosen to use Redis for caching. For that, we need to install additional dependencies.

pnpm install cache-manager-redis-store@2
pnpm install --save-dev @types/cache-manager-redis-store

Now, we will import cache module to enable caching in the toilet.moduel.ts.

imports: [
  CacheModule.registerAsync({
    imports: [ConfigModule],
    useFactory: (config: ConfigService) => ({
      ttl: config.get('REDIS_DEFAULT_TTL'),
      isGlobal: true,
      store: redisStore,
      host: config.get('REDIS_HOST'),
      port: config.get('REDIS_POST'),
    }),
    inject: [ConfigService],
  }),
  //..
]

Notice that I have imported config module to configure Redis. It gives us flexibility to set up for multiple environments - Give proper values for Redis in .env file.

Run Redis locally with Docker

In the docker-compose.yml, we will add the following code to install and run Redis locally using Docker.

services
  redis:
    container_name: cache
    image: redis
    ports:
      - 6379:6379
    volumes:
      - redis:/data
volumes:
  redis:
    driver: local

We can run Redis on the port 6379 locally by entering docker-compose up -d.

Cache a toilet

We will cache a toilet queried to see how caching works in the toilet service.

@Injectable()
export class ToiletsService {
  constructor(
    @Inject(CACHE_MANAGER) private cacheService: Cache,
    //..
  ) {}

  public async getToilet(getToiletArgs: GetToiletArgs): Promise<Toilet> {
    const cachedData = await this.cacheService.get<Toilet>(getToiletArgs.id);
    if (cachedData) return cachedData;

    const toilet = await this.repository.getToilet({
      where: { id: getToiletArgs.id },
    });

    await this.cacheService.set(getToiletArgs.id, toilet);
    return toilet;
  }
  //..
}

We will inject cache manager into the constructor and then implement it in getToilet method. When queried, if the toilet is cached, it will return the cached value. Otherwise, it will return the matched value from the database and store it in Redis.

Check cached values in Redis

To see if cached value is stored in Redis, we can access the Redis docker container and check it using redis-cli.

docker exec -it [redis-container-id] redis-cli
// if accessed

127.0.0.1:6379> GET [id of toilet that was cached]
"{\"id\":\"[id of toilet that was cached]\",\"isPaid\":true,\"price\":1000}"
or
(nil)

When making a toilet query, you will get the toilet information if cached or nil.

Thoughts

As I mentioned in the beginning, our application still does not seem to need caching yet. It is because there is not any complex operation that stays still for a long time and also not a lot of traffic yet. However, it is good to know how caching works and prepare to use it when necessary.

THANKS FOR READING. SEE YOU NEXT TIME!

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