From ffd2a62c3f7df94365980302fef3bc3376b48182 Mon Sep 17 00:00:00 2001
From: Florian Dold <florian.dold@gmail.com>
Date: Mon, 3 Aug 2020 13:00:48 +0530
Subject: modularize repo, use pnpm, improve typechecking

---
 .../taler-wallet-core/src/util/RequestThrottler.ts | 129 +++++++++++++++++++++
 1 file changed, 129 insertions(+)
 create mode 100644 packages/taler-wallet-core/src/util/RequestThrottler.ts

(limited to 'packages/taler-wallet-core/src/util/RequestThrottler.ts')

diff --git a/packages/taler-wallet-core/src/util/RequestThrottler.ts b/packages/taler-wallet-core/src/util/RequestThrottler.ts
new file mode 100644
index 000000000..6f51a72bc
--- /dev/null
+++ b/packages/taler-wallet-core/src/util/RequestThrottler.ts
@@ -0,0 +1,129 @@
+/*
+ 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";
+import { URL } from "./url";
+
+/**
+ * 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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