Caching return value from a service method

Question

I am using nestjs and have just installed the cache-manager module and are trying to cache a response from a service call.

I register the cache module in a sample module (sample.module.ts):

import { CacheInterceptor, CacheModule, Module } from '@nestjs/common';
import { SampleService } from './sample.service';
import { APP_INTERCEPTOR } from '@nestjs/core';
import * as redisStore from 'cache-manager-redis-store';


@Module({
  imports: [
    CacheModule.register({
      ttl: 10,
      store: redisStore,
      host: 'localhost',
      port: 6379,
    }),
 ],
 providers: [
   SampleService,
   {
     provide: APP_INTERCEPTOR,
     useClass: CacheInterceptor,
   }
 ],
 exports: [SampleService],
})
export class SampleModule {}

Then in my service (sample.service.ts):

@Injectable()
export class SampleService {
  @UseInterceptors(CacheInterceptor)
  @CacheKey('findAll')
  async findAll() {
    // Make external API call
  }
}

Looking at redis I can see that nothing is cached for the service method call. If I use the same approach with a controller, then everything works fine and I can see the cached entry in my redis database. I am thinking that there is no way out of the box to cache individual service method calls in nestjs.

Reading the documentation it seems that I am only able to use this approach for controllers, microservices and websockets, but not ordinary services?

Answer 1

Correct, it is not possible to use the cache the same way for services as for controllers.

This is because the magic happens in the CacheInterceptor and Interceptors can only be used in Controllers.

---

However, you can inject the cacheManager into your service and use it directly:

export class SampleService {

  constructor(@Inject(CACHE_MANAGER) protected readonly cacheManager) {}  

  findAll() {
    const value = await this.cacheManager.get(key)
    if (value) {
      return value
    }

    const respone = // ...
    this.cacheManager.set(key, response, ttl)
    return response
  }