implement QuantumKVCache
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Hazelnoot
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@ -5,6 +5,8 @@
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import * as Redis from 'ioredis';
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import { bindThis } from '@/decorators.js';
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import { InternalEventService } from '@/core/InternalEventService.js';
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import { InternalEventTypes } from '@/core/GlobalEventService.js';
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export class RedisKVCache<T> {
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private readonly lifetime: number;
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@ -322,6 +324,10 @@ export class MemoryKVCache<T> {
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clearInterval(this.gcIntervalHandle);
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}
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public get size() {
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return this.cache.size;
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}
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public get entries() {
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return this.cache.entries();
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}
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@ -410,3 +416,230 @@ export class MemorySingleCache<T> {
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return value;
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}
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}
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export interface QuantumKVOpts<T> {
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/**
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* Memory cache lifetime in milliseconds.
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*/
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lifetime: number;
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/**
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* Callback to fetch the value for a key that wasn't found in the cache.
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* May be synchronous or async.
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*/
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fetcher: (key: string, cache: QuantumKVCache<T>) => T | Promise<T>;
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/**
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* Optional callback when a value is created or changed in the cache, either locally or elsewhere in the cluster.
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* This is called *after* the cache state is updated.
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* May be synchronous or async.
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*/
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onSet?: (key: string, cache: QuantumKVCache<T>) => void | Promise<void>;
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/**
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* Optional callback when a value is deleted from the cache, either locally or elsewhere in the cluster.
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* This is called *after* the cache state is updated.
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* May be synchronous or async.
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*/
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onDelete?: (key: string, cache: QuantumKVCache<T>) => void | Promise<void>;
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}
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/**
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* QuantumKVCache is a lifetime-bounded memory cache (like MemoryKVCache) with automatic cross-cluster synchronization via Redis.
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* All nodes in the cluster are guaranteed to have a *subset* view of the current accurate state, though individual processes may have different items in their local cache.
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* This ensures that a call to get() will never return stale data.
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*/
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export class QuantumKVCache<T> implements Iterable<[key: string, value: T]> {
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private readonly memoryCache: MemoryKVCache<T>;
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private readonly fetcher: QuantumKVOpts<T>['fetcher'];
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private readonly onSet: QuantumKVOpts<T>['onSet'];
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private readonly onDelete: QuantumKVOpts<T>['onDelete'];
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/**
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* @param internalEventService Service bus to synchronize events.
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* @param name Unique name of the cache - must be the same in all processes.
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* @param opts Cache options
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*/
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constructor(
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private readonly internalEventService: InternalEventService,
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private readonly name: string,
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opts: QuantumKVOpts<T>,
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) {
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this.memoryCache = new MemoryKVCache(opts.lifetime);
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this.fetcher = opts.fetcher;
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this.onSet = opts.onSet;
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this.onDelete = opts.onDelete;
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this.internalEventService.on('quantumCacheUpdated', this.onQuantumCacheUpdated, {
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// Ignore our own events, otherwise we'll immediately erase any set value.
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ignoreLocal: true,
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});
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}
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/**
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* The number of items currently in memory.
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* This applies to the local subset view, not the cross-cluster cache state.
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*/
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public get size() {
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return this.memoryCache.size;
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}
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/**
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* Iterates all [key, value] pairs in memory.
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* This applies to the local subset view, not the cross-cluster cache state.
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*/
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@bindThis
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public *entries(): Generator<[key: string, value: T]> {
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for (const entry of this.memoryCache.entries) {
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yield [entry[0], entry[1].value];
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}
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}
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/**
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* Iterates all keys in memory.
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* This applies to the local subset view, not the cross-cluster cache state.
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*/
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@bindThis
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public *keys() {
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for (const entry of this.memoryCache.entries) {
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yield entry[0];
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}
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}
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/**
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* Iterates all values pairs in memory.
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* This applies to the local subset view, not the cross-cluster cache state.
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*/
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@bindThis
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public *values() {
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for (const entry of this.memoryCache.entries) {
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yield entry[1].value;
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}
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}
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/**
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* Creates or updates a value in the cache, and erases any stale caches across the cluster.
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* Fires an onSet event after the cache has been updated in all processes.
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* Skips if the value is unchanged.
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*/
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@bindThis
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public async set(key: string, value: T): Promise<void> {
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if (this.memoryCache.get(key) === value) {
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return;
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}
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this.memoryCache.set(key, value);
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await this.internalEventService.emit('quantumCacheUpdated', { name: this.name, op: 's', key });
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if (this.onSet) {
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await this.onSet(key, this);
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}
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}
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/**
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* Gets or fetches a value from the cache.
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* Fires an onSet event, but does not emit an update event to other processes.
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*/
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@bindThis
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public async get(key: string): Promise<T> {
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let value = this.memoryCache.get(key);
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if (value === undefined) {
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value = await this.fetcher(key, this);
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this.memoryCache.set(key, value);
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if (this.onSet) {
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await this.onSet(key, this);
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}
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}
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return value;
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}
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/**
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* Alias to get(), included for backwards-compatibility with RedisKVCache.
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* @deprecated use get() instead
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*/
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@bindThis
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public async fetch(key: string): Promise<T> {
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return await this.get(key);
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}
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/**
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* Returns true is a key exists in memory.
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* This applies to the local subset view, not the cross-cluster cache state.
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*/
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@bindThis
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public has(key: string): boolean {
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return this.memoryCache.get(key) !== undefined;
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}
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/**
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* Deletes a value from the cache, and erases any stale caches across the cluster.
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* Fires an onDelete event after the cache has been updated in all processes.
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*/
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@bindThis
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public async delete(key: string): Promise<void> {
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this.memoryCache.delete(key);
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await this.internalEventService.emit('quantumCacheUpdated', { name: this.name, op: 'd', key });
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if (this.onDelete) {
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await this.onDelete(key, this);
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}
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}
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/**
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* Refreshes the value of a key from the fetcher, and erases any stale caches across the cluster.
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* Fires an onSet event after the cache has been updated in all processes.
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*/
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@bindThis
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public async refresh(key: string): Promise<T> {
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const value = await this.fetcher(key, this);
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await this.set(key, value);
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return value;
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}
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/**
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* Erases all entries from the local memory cache.
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* Does not send any events or update other processes.
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*/
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@bindThis
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public gc() {
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this.memoryCache.gc();
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}
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/**
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* Erases all data and disconnects from the cluster.
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* This *must* be called when shutting down to prevent memory leaks!
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*/
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@bindThis
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public dispose() {
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this.internalEventService.off('quantumCacheUpdated', this.onQuantumCacheUpdated);
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this.memoryCache.dispose();
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}
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@bindThis
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private async onQuantumCacheUpdated(data: InternalEventTypes['quantumCacheUpdated']): Promise<void> {
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if (data.name === this.name) {
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this.memoryCache.delete(data.key);
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if (data.op === 's' && this.onSet) {
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await this.onSet(data.key, this);
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}
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if (data.op === 'd' && this.onDelete) {
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await this.onDelete(data.key, this);
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}
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}
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}
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/**
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* Iterates all [key, value] pairs in memory.
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* This applies to the local subset view, not the cross-cluster cache state.
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*/
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[Symbol.iterator](): Iterator<[key: string, value: T]> {
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return this.entries();
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}
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}
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