51 lines
1.6 KiB
JavaScript
51 lines
1.6 KiB
JavaScript
'use strict'
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const { LruMap: Lru } = require('toad-cache')
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function LocalStore (continueExceeding, exponentialBackoff, cache = 5000) {
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this.continueExceeding = continueExceeding
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this.exponentialBackoff = exponentialBackoff
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this.lru = new Lru(cache)
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}
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LocalStore.prototype.incr = function (ip, cb, timeWindow, max) {
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const nowInMs = Date.now()
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let current = this.lru.get(ip)
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if (!current) {
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// Item doesn't exist
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current = { current: 1, ttl: timeWindow, iterationStartMs: nowInMs }
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} else if (current.iterationStartMs + timeWindow <= nowInMs) {
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// Item has expired
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current.current = 1
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current.ttl = timeWindow
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current.iterationStartMs = nowInMs
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} else {
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// Item is alive
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++current.current
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// Reset TLL if max has been exceeded and `continueExceeding` is enabled
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if (this.continueExceeding && current.current > max) {
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current.ttl = timeWindow
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current.iterationStartMs = nowInMs
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} else if (this.exponentialBackoff && current.current > max) {
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// Handle exponential backoff
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const backoffExponent = current.current - max - 1
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const ttl = timeWindow * (2 ** backoffExponent)
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current.ttl = Number.isSafeInteger(ttl) ? ttl : Number.MAX_SAFE_INTEGER
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current.iterationStartMs = nowInMs
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} else {
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current.ttl = timeWindow - (nowInMs - current.iterationStartMs)
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}
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}
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this.lru.set(ip, current)
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cb(null, current)
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}
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LocalStore.prototype.child = function (routeOptions) {
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return new LocalStore(routeOptions.continueExceeding, routeOptions.exponentialBackoff, routeOptions.cache)
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}
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module.exports = LocalStore
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