How to control cache in Nestjs?

Question

I read the doc of nestjs recently, and learned something from it.

But I found something that puzzled me.

In Techniques/Caching, the doc shows me to use a decorator like @UseInterceptors(CacheInterceptor) on a controller to cache its response (default track by route).

I wrote a testcase and found it's useful. But I didn't find any explanation to show how to clean the cache. That means I have to wait for the cache to expire.

In my opinion, a cache store must provide an API to clear the cache by key, so that it can update the cache when data changes (by explicitly calling a clear API).

Is there any way to do that?

Solution 1

You can inject the underlying cache-manager instance with @Inject(CACHE_MANAGER). On the cache-manager instance you can then call the method del(key, cb) to clear the cache for a specified key, see the docs.

Example

counter = 0;
constructor(@Inject(CACHE_MANAGER) private cacheManager) {}

// The first call increments to one, the preceding calls will be answered by the cache
// without incrementing the counter. Only after you clear the cache by calling /reset
// the counter will be incremented once again.
@Get()
@UseInterceptors(CacheInterceptor)
incrementCounter() {
  this.counter++;
  return this.counter;
}

// Call this endpoint to reset the cache for the route '/'
@Get('reset')
resetCache() {
  const routeToClear = '/';
  this.cacheManager.del(routeToClear, () => console.log('clear done'));
}

Solution 2

You could also use another approach, you could use utils-decorators lib (npm install --save utils-decorators) and take advantage of the AsyncMemoize decorator. Then you only need to add a decorator to you controller function:

import {memoizeAsync} from 'utils-decorators';

const cache = new Map();

class Controller {


 @Get()
 @memoizeAsync({cache: cache})
 incrementCounter() {
  this.counter++;

  return this.counter;
 }

 @Get('reset')
 resetCache() {
   // do whatever you want with the cache map.
 }
}

Comments

[Sohel Ahmed Mesaniya]

Hi @kim-kern . Thanks for the answer. I would like to know what is the data type of cacheManager variable (@Inject(CACHE_MANAGER) private cacheManager)

[Kim Kern]

@SohelAhmedM Try npm install --save-dev @types/cache-manager

[Sohel Ahmed Mesaniya]

I have added a simple minimal nestjs-redis-cache example - gist.github.com/SOHELAHMED7/f7396fb7711aad9538e149e1b811b53c

[Vallie]

Is there a way we can enable and disable entire caching feature via a flag(true/false) in config

[Kim Kern]

@Vallie It's hard to answer your question without seeing more details. When is the flag set? Statically on server start or dynamically? How is it set? ... Please open a new question and include a code example that describes your use case. :-)

[Vallie]

Posted here stackoverflow.com/questions/63942382/…