@bugsnag/core-performance/dist/probability-manager.js

Core performance client

// the time between requests to fetch a new probability value from the server
const PROBABILITY_REFRESH_MILLISECONDS = 24 * 60 * 60 * 1000; // 24 hours
class ProbabilityManager {
    static async create(persistence, sampler, probabilityFetcher) {
        const persistedProbability = await persistence.load('bugsnag-sampling-probability');
        let initialProbabilityTime;
        if (persistedProbability === undefined) {
            // If there is no stored probability:
            // - Set the initial probability value to the default
            // - Immediately fetch a new probability value
            sampler.probability = 1.0;
            initialProbabilityTime = 0;
        }
        else if (persistedProbability.time < Date.now() - PROBABILITY_REFRESH_MILLISECONDS) {
            // If it is >= 24 hours old:
            // - Set the initial probability value to the stored value
            // - Immediately fetch a new probability value
            sampler.probability = persistedProbability.value;
            initialProbabilityTime = persistedProbability.time;
        }
        else {
            // If it is < 24 hours old:
            // - Use the stored probability
            // - Fetch a new probability when this value would be 24 hours old
            sampler.probability = persistedProbability.value;
            initialProbabilityTime = persistedProbability.time;
        }
        return new ProbabilityManager(persistence, sampler, probabilityFetcher, initialProbabilityTime);
    }
    constructor(persistence, sampler, probabilityFetcher, initialProbabilityTime) {
        this.outstandingFreshnessCheck = undefined;
        this.persistence = persistence;
        this.sampler = sampler;
        this.probabilityFetcher = probabilityFetcher;
        this.lastProbabilityTime = initialProbabilityTime;
        this.ensureFreshProbability();
    }
    setProbability(newProbability) {
        this.lastProbabilityTime = Date.now();
        this.sampler.probability = newProbability;
        // return this promise for convience in unit tests as it allows us to wait
        // for persistence to finish; in real code we won't ever wait for this but
        // there's no harm in returning it anyway
        return this.persistence.save('bugsnag-sampling-probability', {
            value: newProbability,
            time: this.lastProbabilityTime
        });
    }
    /**
     * Ensure that the current probability value is fresh, i.e. it is less than 24
     * hours old
     *
     * If the probability value is stale then this method will fetch a fresh one
     *
     * This method is idempotent; calling it while there is already an outstanding
     * probability request will not create a second request
     */
    ensureFreshProbability() {
        // we're already fetching a new probability
        if (this.outstandingFreshnessCheck) {
            return this.outstandingFreshnessCheck;
        }
        // if the probability value is >= 24 hours old, fetch a new one
        if (Date.now() - this.lastProbabilityTime >= PROBABILITY_REFRESH_MILLISECONDS) {
            this.outstandingFreshnessCheck = this.probabilityFetcher.getNewProbability()
                .then(probability => {
                this.setProbability(probability);
                this.outstandingFreshnessCheck = undefined;
            });
            return this.outstandingFreshnessCheck;
        }
        return Promise.resolve();
    }
}

export { ProbabilityManager as default };