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feat(express): add lru cache for wallets in v2 /sendcoins
B2B2C clients exprience high latencies for get wallet requests. To mitigate, we will cache these requests TICKET: CS-4503
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,91 @@ | ||
| export interface LRUCacheOptions { | ||
| // maximum number of records this cache can hold | ||
| maxSize: number; | ||
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| // duration in milliseconds after which a record is considered expired | ||
| ttl: number; | ||
| } | ||
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| export default class LRUCache<K, V> { | ||
| private cache: Map<K, { value: V; expiry: number }>; | ||
| private readonly maxSize: number; | ||
| private readonly ttl: number; | ||
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| /** | ||
| * Creates a new LRU cache | ||
| * @param options configurable options for this cache | ||
| */ | ||
| constructor(options: LRUCacheOptions = { maxSize: 10, ttl: 60000 }) { | ||
| this.cache = new Map(); | ||
| this.maxSize = options.maxSize; | ||
| this.ttl = options.ttl; | ||
| } | ||
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| /** | ||
| * Retrieves value from cache if it exists and has not expired | ||
| * @param key key | ||
| */ | ||
| get(key: K): V | undefined { | ||
| const cacheItem = this.cache.get(key); | ||
| if (cacheItem) { | ||
| // If expired, delete the cache item | ||
| if (Date.now() > cacheItem.expiry) { | ||
| this.cache.delete(key); | ||
| return undefined; | ||
| } | ||
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| // Move the item to the end to mark it as recently used | ||
| this.cache.delete(key); | ||
| this.cache.set(key, cacheItem); | ||
| return cacheItem.value; | ||
| } | ||
| return undefined; | ||
| } | ||
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| /** | ||
| * Adds a new item to the cache. | ||
| * If the cache is full, it will try to evict expired items first. | ||
| * If no expired items are found, it will evict the least recently used item. | ||
| * | ||
| * @param key key | ||
| * @param value value | ||
| */ | ||
| set(key: K, value: V): void { | ||
| const expiry = Date.now() + this.ttl; | ||
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| if (this.cache.has(key)) { | ||
| this.cache.delete(key); | ||
| } | ||
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| // If cache is full, remove expired items, then remove the least recently used (LRU) item | ||
| if (this.cache.size >= this.maxSize) { | ||
| const numExpiredEvicted = this.cleanUpExpiredItems(); | ||
| if (numExpiredEvicted === 0) { | ||
| const firstKey = this.cache.keys().next().value; // Get the first key (LRU) | ||
| this.cache.delete(firstKey); | ||
| } | ||
| } | ||
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| // Add the new item to the cache | ||
| this.cache.set(key, { value, expiry }); | ||
| } | ||
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| delete(key: K): boolean { | ||
| return this.cache.delete(key); | ||
| } | ||
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| // Check if an item has expired | ||
| private cleanUpExpiredItems(): number { | ||
| const now = Date.now(); | ||
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| let numDeleted = 0; | ||
| for (const [key, { expiry }] of this.cache.entries()) { | ||
| if (now > expiry) { | ||
| this.cache.delete(key); | ||
| numDeleted++; | ||
| } | ||
| } | ||
|
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| return numDeleted; | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,37 @@ | ||
| import * as should from 'should'; | ||
| import LRUCache from '../../src/LRUCache'; | ||
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| describe('LRUCache', function () { | ||
| let cache: LRUCache<string, string>; | ||
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| beforeEach(() => { | ||
| cache = new LRUCache<string, string>({ | ||
| maxSize: 3, | ||
| ttl: 5000, | ||
| }); | ||
| }); | ||
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| it('should store and retrieve values correctly', () => { | ||
| cache.set('a', 'apple'); | ||
| cache.set('b', 'banana'); | ||
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| 'apple'.should.equal(cache.get('a')); | ||
| 'banana'.should.equal(cache.get('b')); | ||
| }); | ||
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| it('should return undefined for non-existing keys', () => { | ||
| should.equal(cache.get('does-not-exist'), undefined); | ||
| }); | ||
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| it('should evict the least recently used item when the cache exceeds the max size', () => { | ||
| cache.set('a', 'apple'); | ||
| cache.set('b', 'banana'); | ||
| cache.set('c', 'cherry'); | ||
| cache.set('d', 'date'); | ||
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| should.equal(cache.get('a'), undefined); | ||
| 'banana'.should.equal(cache.get('b')); | ||
| 'cherry'.should.equal(cache.get('c')); | ||
| 'date'.should.equal(cache.get('d')); | ||
| }); | ||
| }); |