491f0cd08a
* Copyright headers 1 * Licence headers 2 * Copyright Headers 3 * Copyright Headers 4 * Copyright Headers 5 * Copyright Headers 6 * Copyright headers 7 * Add copyright headers for html and config file * Replace license files and update package.json * Update with CLA * lint
54 lines
2.6 KiB
TypeScript
54 lines
2.6 KiB
TypeScript
/*
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Copyright 2024 New Vector Ltd.
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SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only
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Please see LICENSE files in the repository root for full details.
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*/
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import { xxHash32 } from "js-xxhash";
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/**
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* The PhasedRolloutFeature class is used to manage the phased rollout of a new feature.
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*
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* It uses a hash of the user's identifier and the feature name to determine if a feature is enabled for a specific user.
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* The rollout percentage determines the probability that a user will be enabled for the feature.
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* The feature will be enabled for all users if the rollout percentage is 100, and for no users if the percentage is 0.
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* If a user is enabled for a feature at x% rollout, it will also be for any greater than x percent.
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*
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* The process ensures a uniform distribution of enabled features across users.
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*
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* @property featureName - The name of the feature to be rolled out.
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* @property rolloutPercentage - The int percentage (0..100) of users for whom the feature should be enabled.
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*/
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export class PhasedRolloutFeature {
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public readonly featureName: string;
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private readonly rolloutPercentage: number;
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private readonly seed: number;
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public constructor(featureName: string, rolloutPercentage: number) {
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this.featureName = featureName;
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if (!Number.isInteger(rolloutPercentage) || rolloutPercentage < 0 || rolloutPercentage > 100) {
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throw new Error("Rollout percentage must be an integer between 0 and 100");
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}
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this.rolloutPercentage = rolloutPercentage;
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// We add the feature name for the seed to ensure that the hash is different for each feature
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this.seed = Array.from(featureName).reduce((sum, char) => sum + char.charCodeAt(0), 0);
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}
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/**
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* Returns true if the feature should be enabled for the given user.
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* @param userIdentifier - Some unique identifier for the user, e.g. their user ID or device ID.
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*/
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public isFeatureEnabled(userIdentifier: string): boolean {
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/*
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* We use a hash function to convert the unique user ID string into an integer.
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* This integer can then be used as a basis for deciding whether the user should have access to the new feature.
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* We need some hash with good uniform distribution properties, security is not a concern here.
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* We use xxHash32, which is fast and has good distribution properties.
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*/
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const hash = xxHash32(userIdentifier, this.seed);
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// We use the hash modulo 100 to get a number between 0 and 99.
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// Modulo is simple and effective and the distribution should be uniform enough for our purposes.
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return hash % 100 < this.rolloutPercentage;
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}
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}
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