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diff --git a/src/util/RequestThrottler.ts b/src/util/RequestThrottler.ts
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+++ b/src/util/RequestThrottler.ts
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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, Timestamp } from "../walletTypes";
+
+/**
+ * Maximum request per second, per origin.
+ */
+const MAX_PER_SECOND = 20;
+
+/**
+ * Maximum request per minute, per origin.
+ */
+const MAX_PER_MINUTE = 100;
+
+/**
+ * Maximum request per hour, per origin.
+ */
+const MAX_PER_HOUR = 5000;
+
+
+/**
+ * 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 = now.t_ms - this.lastUpdate.t_ms;
+    this.tokensSecond = Math.max(MAX_PER_SECOND, this.tokensSecond + (d / 1000));
+    this.tokensMinute = Math.max(MAX_PER_MINUTE, this.tokensMinute + (d / 1000 * 60));
+    this.tokensHour = Math.max(MAX_PER_HOUR, this.tokensHour + (d / 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();
+  }
+}