@criipto/cache

node-cache

Cache implementations for Node.js/TypeScript

Policies

All the cache implementations allow you to inject policy decision callbacks.

Policies help you define how the cache should behave when it is updating or hold stale data.

import {CacheUpdatePolicy, CachePendingPolicy} from '@criipto/cache';

CacheUpdatePolicy

• CacheUpdatePolicy.UPDATE: Trigger update of value for cache key
• CacheUpdatePolicy.DONT_UPDATE: No-op, keep current value

CachePendingPolicy

• CachePendingPolicy.WAIT: Blocks the read while waiting for cache refresh to finish
• CachePendingPolicy.STALE: Return stale cache data while the cache updates

Memory backed cache

Example

import {CacheUpdatePolicy, CachePendingPolicy, memoryCache} from '@criipto/cache';

const metadataCache = memoryCache({
  updatePolicy: (url, {lastUpdatedAt}) => {
    // Update metadata if data is more than an hour old
    if (lastUpdatedAt.valueOf() < (Date.now() - 60 * 60 * 1000)) {
      return CacheUpdatePolicy.UPDATE;
    }
    return CacheUpdatePolicy.DONT_UPDATE;
  },
  pendingPolicy: () => CachePendingPolicy.STALE,
  refresh: async (url: URL) => {
    return await fetch(url);
  }
});

Storage backed cache

Example

import {CacheUpdatePolicy, CachePendingPolicy, storedCache} from '@criipto/cache';

const metadataCache = storedCache({
  updatePolicy: (url, {lastUpdatedAt}) => {
    // Update metadata if data is more than an hour old
    if (lastUpdatedAt.valueOf() < (Date.now() - 60 * 60 * 1000)) {
      return CacheUpdatePolicy.UPDATE;
    }
    return CacheUpdatePolicy.DONT_UPDATE;
  },
  pendingPolicy: () => CachePendingPolicy.STALE,
  refresh: async (url: URL) => {
    const response = await fetch(url);
    if (response.status !== 200) throw new Error('Not 200');
    return response.json() as Promise<{metadata: string}>
  },
  storage: {
    getItem: async (url) => {
      return await fetchFromStorageImplementation(url);
    },
    setItem: async (url, data) => {
      return await upsertInStorageImplementation(url, data);
    }
  }
});