@bitblit/ratchet-aws/lib/cache/simple-cache.js

Common tools for use with AWS browser and node

import { Logger } from '@bitblit/ratchet-common/logger/logger';
export class SimpleCache {
    provider;
    defaultTimeToLiveMS;
    constructor(provider, defaultTimeToLiveMS = 1_000 * 60) {
        this.provider = provider;
        this.defaultTimeToLiveMS = defaultTimeToLiveMS;
    }
    createDefaultReadOptions() {
        return {
            maxStalenessMS: null,
            timeToLiveMS: this.defaultTimeToLiveMS,
            cacheNullValues: false,
        };
    }
    async fetchWrapper(cacheKey, producer, opts = this.createDefaultReadOptions()) {
        Logger.silly('Fetching %s', cacheKey);
        const now = new Date().getTime();
        let rval = await this.provider.readFromCache(cacheKey);
        if (rval && rval.expiresEpochMS < now) {
            Logger.debug('Object found, but expired - removing');
            rval = null;
        }
        if (rval && opts && opts.maxStalenessMS && now - rval.createdEpochMS > opts.maxStalenessMS) {
            Logger.debug('Object found by too stale - removing');
            rval = null;
        }
        if (!rval) {
            Logger.debug('%s not found in cache, generating', cacheKey);
            const tmp = await producer();
            if (tmp || opts?.cacheNullValues) {
                Logger.debug('Writing %j to cache');
                rval = {
                    cacheKey: cacheKey,
                    createdEpochMS: now,
                    expiresEpochMS: opts && opts.timeToLiveMS ? now + opts.timeToLiveMS : null,
                    value: tmp,
                    generated: false,
                };
                await this.provider.storeInCache(rval);
                rval.generated = true;
            }
        }
        return rval;
    }
    async fetch(cacheKey, producer, opts = null) {
        const wrapper = await this.fetchWrapper(cacheKey, producer, opts);
        return wrapper ? wrapper.value : null;
    }
    async removeFromCache(cacheKey, returnOldValue) {
        let rval = null;
        if (returnOldValue) {
            rval = await this.fetchWrapper(cacheKey, () => null);
        }
        await this.provider.removeFromCache(cacheKey);
        return rval;
    }
    async clearCache() {
        return this.provider.clearCache();
    }
    async readAll() {
        return this.provider.readAll();
    }
}
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