back-off.js

back-off.js

/**
 * Generalised back-off function. 
 * @param {Function} unary The unary operator function that returns the next state given the current state (current value and invocation count).
 * @param {Number} initial The initial value to start the back-off.
 * @example const multiplyTenBackOff = backOff((current, count) => current * 10);
 * @example const negativeBackOff = backOff((current, count) => current - 1, 1000);
 */
const backOff = (unary, initial = 0) => {
    let current = initial;
    let count = 0;

    const func = () => {
        count = count + 1;
        current = unary(current, count);
        return current;
    };

    return func;
};

/**
 * Incremental back-off function.
 * @param {Number} increment The amount to increment the back-off.
 * @param {Number} initial The initial value to start the back-off.
 */
const incrementalBackOff = (increment = 1, initial = 0) => {
    let current = initial;

    const func = () => {
        current = current + increment;
        return current;
    };

    return func;
};

/**
 * Incremental back-off function with random jitter to avoid collision.
 * @param {Number} increment The amount to increment the back-off.
 * @param {Number} initial The initial value to start the back-off.
 */
const incrementalJitterBackOff = (increment = 1, initial = 1) => {
    let current = initial;

    const func = () => {
        current = current + increment + Math.round(Math.random() * 100);
        return current;
    };

    return func;
};

export {
    backOff,
    incrementalBackOff,
    incrementalJitterBackOff
};