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| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 | 1x 1x 63x 63x 63x 63x 63x 34x 34x 34x 34x 34x 39x 23x 16x 16x 5x 11x 34x 34x 11x 1x 11x 8x 3x 1x | const noop = require('node-noop').noop
const precond = require('precond')
/**
* @class
* @classdesc An abstract class, defining the skeleton for a backoff strategy,
* it is expected that this will be subclassed, with an implementation of
* _intervalFunc
*/
class BackoffStrategy {
/**
* @param {Integer} [retries=3] The total number of attempts a backoff strategy will perform
* @param {Integer} [maxDelay=0] The maximum delay before retrying, 0 = no max.
*/
constructor (retries = 3, maxDelay = 0) {
precond.checkArgument(retries > 0, 'retries must be an integer > 0')
this.retries = retries
this.maxDelay = maxDelay
this.func = noop
this.lastDelay = 0
}
/**
* starts the execution of "func", backing off at some Interval.
* @param {Function} [func=noop] - the function to execute, must have a signature of () => Promise
* @param {Integer} [retries=1] How many times func will be called before giving up
* @param {Integer} [maxDelay=0] The maximum interval of time to wait when retrying
* @return {Promise}
*/
execute ({ func = this.func, retries = this.retries, maxDelay = this.maxDelay }) {
this.func = func
this.lastDelay = 0
const retry = new Promise((resolve, reject) => {
let attempt = 1
const loop = () => {
this
.func()
.then(res => resolve(res))
.catch((err) => {
attempt += 1
if ((retries === 0) || (attempt <= retries)) {
return setTimeout(
loop,
this._scheduleNextTry(attempt, maxDelay)
)
}
return reject(err)
})
}
loop()
})
return retry
}
/**
* Calculates the next delay before executing func
* @param {Integer} attempt
* @param {Integer} maxDelay
*/
_scheduleNextTry (attempt, maxDelay = 0) {
if (maxDelay < 0) {
maxDelay = 0
}
if (maxDelay === 0) {
return this._intervalFunc(attempt)
}
return Math.min(this._intervalFunc(attempt), maxDelay)
}
}
module.exports = BackoffStrategy
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