ts-cache-decorators

Install

npm i @t.voslar/ts-cache-decorator

Configuration

Choose one of the supported storages (MemcacheElastiCache or RedisStorage) or create your new storage which implements IStorage.

const cacheStorage = new MemcachedElastiCacheStorage('localhost:11211', {})
useStorage(cacheStorage)

Now you can use @Cache decorator

@Cache({ type: 'normal', cacheKey: 'getUser', ttl: 3 })
async getUser (userId: string): Promise<User> {

Above caching will take cacheKey + parameters (which is just userId in this case) and will create cache key, which will expire after 3 seconds.

If you need to filter some parameters you can use filterParams param.

@Cache({ type: 'normal', cacheKey: 'getUser', ttl: 3, filterParams: ['otherParam'] })
async getUser (userId: string, otherParam: boolean): Promise<User> {

Concurrent misses

Calls that miss the same key at the same time are collapsed into one: the first caller runs the method, the rest await its result. Without that, a burst of traffic against a cold or just-expired key runs the underlying work once per caller - the cache only starts absorbing load after the first call has finished writing, which is the opposite of what you want at exactly that moment.

// getUser runs once, not five times
await Promise.all([
  service.getUser('1'),
  service.getUser('1'),
  service.getUser('1'),
  service.getUser('1'),
  service.getUser('1')
])

This is per-process. It deduplicates within one Node instance, not across a cluster, so with N replicas the worst case is N concurrent computations rather than N x (concurrent requests per replica). Going further needs a distributed lock, which is a heavier thing to put in the read path of a cache.

A failed call is not cached and does not wedge the key - every waiter on that call rejects, and the next caller retries.

Cache API

| Param | Value | Description | | ---- | ---- | --- | | type | 'normal' | Type of cache. | | cacheKey | string | Caching key. | | ttl | number | Time to live. | | filterParams | string[] | Parameters which should not be inside cache key. |