@apollo/utils.keyvaluecache
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3.1.0 • Public • Published

KeyValueCache interface

export interface KeyValueCache<
  V = string,
  SO extends KeyValueCacheSetOptions = KeyValueCacheSetOptions,
> {
  get(key: string): Promise<V | undefined>;
  set(key: string, value: V, options?: SO): Promise<void>;
  delete(key: string): Promise<boolean | void>;
}

This interface defines a minimally-compatible cache intended for (but not limited to) use by Apollo Server. It is notably implemented by KeyvAdapter from the @apollo/utils.keyvadapter package. (KeyvAdapter in conjunction with a Keyv is probably more interesting to you unless you're actually building a cache!)

InMemoryLRUCache

This class wraps lru-cache and implements the KeyValueCache interface. It accepts LRUCache.Options as the constructor argument and passes them to the LRUCache which is created. A default maxSize and sizeCalculator are provided in order to prevent an unbounded cache; these can both be tweaked via the constructor argument.

const cache = new InMemoryLRUCache({
  // create a larger-than-default `LRUCache`
  maxSize: Math.pow(2, 20) * 50,
});

PrefixingKeyValueCache

This class wraps a KeyValueCache in order to provide a specified prefix for keys entering the cache via this wrapper.

const cache = new InMemoryLRUCache();
const prefixedCache = new PrefixingKeyValueCache(cache, "apollo:");

One reason to use this is if a single piece of software wants to use a cache for multiple features. For example, you can pass a KeyValueCache as the cache option to @apollo/server's ApolloServer class; it provides this cache to plugins and other features as a default cache to use (if the user does not provide the specific plugin its own cache). Each feature uses PrefixingKeyValueCache with a different prefix to prevent different features from stomping on each others' data.

However, if you are configuring one of those features explicitly, you may not want this prefix to be added. In that case, you can wrap your cache in a cache returned by PrefixingKeyValueCache.cacheDangerouslyDoesNotNeedPrefixesForIsolation. The only difference between this cache and the cache that it wraps is that when it is passed directly to a PrefixingKeyValueCache, no prefix is applied.

That is, let's say you are using a class that is implemented like this:

class SomePlugin {
  private cache: KeyValueCache;
  constructor(cache: KeyValueCache) {
    this.cache = new PrefixingKeyValueCache(cache, "some:");
  }
}

If you set up your plugin as new SomePlugin({ cache: myRedisCache }) then the plugin will add some: to all keys when interacting with your cache, but if you set it up as new SomePlugin({ cache: PrefixingKeyValueCache.cacheDangerouslyDoesNotNeedPrefixesForIsolation(myRedisCache) }), then the plugin will not apply its prefix. You should only do this if you feel confident that this feature's use of this cache will not overlap with another feature: perhaps this is the only feature you have configured to use this cache, or perhaps the feature provides suitable control over cache keys that you can ensure isolation without needing the plugin's prefix.

Software like ApolloServer that passes a single KeyValueCache to several features should throw if a PrefixesAreUnnecessaryForIsolationCache is provided to it; it can check this condition with the static PrefixingKeyValueCache.prefixesAreUnnecessaryForIsolation method (which is safer than an instanceof check in case there are multiple copies of @apollo/utils.keyvaluecache installed).

ErrorsAreMissesCache

This class wraps a KeyValueCache in order to provide error tolerance for caches which connect via a client like Redis. In the event that there's an error, this wrapper will treat it as a cache miss (and log the error instead, if a logger is provided).

An example usage (which makes use of the keyv Redis client and our KeyvAdapter) would look something like this:

import Keyv from "keyv";
import { KeyvAdapter } from "@apollo/utils.keyvadapter";
import { ErrorsAreMissesCache } from "@apollo/utils.keyvaluecache";

const redisCache = new Keyv("redis://user:pass@localhost:6379");
const faultTolerantCache = new ErrorsAreMissesCache(
  new KeyvAdapter(redisCache),
);

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