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/*
This file is part of GNU Taler
(C) 2019 GNUnet e.V.
GNU Taler is free software; you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the Free Software
Foundation; either version 3, or (at your option) any later version.
TALER is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with
GNU Taler; see the file COPYING. If not, see <http://www.gnu.org/licenses/>
*/
/**
* Implementation of token bucket throttling.
*/
/**
* Imports.
*/
import { getTimestampNow, timestampDifference } from "../util/time";
/**
* Maximum request per second, per origin.
*/
const MAX_PER_SECOND = 50;
/**
* Maximum request per minute, per origin.
*/
const MAX_PER_MINUTE = 100;
/**
* Maximum request per hour, per origin.
*/
const MAX_PER_HOUR = 1000;
/**
* Throttling state for one origin.
*/
class OriginState {
private tokensSecond: number = MAX_PER_SECOND;
private tokensMinute: number = MAX_PER_MINUTE;
private tokensHour: number = MAX_PER_HOUR;
private lastUpdate = getTimestampNow();
private refill(): void {
const now = getTimestampNow();
const d = timestampDifference(now, this.lastUpdate);
if (d.d_ms === "forever") {
throw Error("assertion failed");
}
const d_s = d.d_ms / 1000;
this.tokensSecond = Math.min(
MAX_PER_SECOND,
this.tokensSecond + d_s / 1000,
);
this.tokensMinute = Math.min(
MAX_PER_MINUTE,
this.tokensMinute + (d_s / 1000) * 60,
);
this.tokensHour = Math.min(
MAX_PER_HOUR,
this.tokensHour + (d_s / 1000) * 60 * 60,
);
this.lastUpdate = now;
}
/**
* Return true if the request for this origin should be throttled.
* Otherwise, take a token out of the respective buckets.
*/
applyThrottle(): boolean {
this.refill();
if (this.tokensSecond < 1) {
console.log("request throttled (per second limit exceeded)");
return true;
}
if (this.tokensMinute < 1) {
console.log("request throttled (per minute limit exceeded)");
return true;
}
if (this.tokensHour < 1) {
console.log("request throttled (per hour limit exceeded)");
return true;
}
this.tokensSecond--;
this.tokensMinute--;
this.tokensHour--;
return false;
}
}
/**
* Request throttler, used as a "last layer of defense" when some
* other part of the re-try logic is broken and we're sending too
* many requests to the same exchange/bank/merchant.
*/
export class RequestThrottler {
private perOriginInfo: { [origin: string]: OriginState } = {};
/**
* Get the throttling state for an origin, or
* initialize if no state is associated with the
* origin yet.
*/
private getState(origin: string): OriginState {
const s = this.perOriginInfo[origin];
if (s) {
return s;
}
const ns = (this.perOriginInfo[origin] = new OriginState());
return ns;
}
/**
* Apply throttling to a request.
*
* @returns whether the request should be throttled.
*/
applyThrottle(requestUrl: string): boolean {
const origin = new URL(requestUrl).origin;
return this.getState(origin).applyThrottle();
}
}
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