fix(util-retry): detect throttling from RetryErrorInfo.errorType in DefaultRateLimiter

.changeset/fix-rate-limiter-throttle-detection.md

@@ -0,0 +1,5 @@
+---
+"@smithy/util-retry": patch
+---
+
+fix(util-retry): detect throttling errors from RetryErrorInfo.errorType in DefaultRateLimiter

packages/util-retry/src/DefaultRateLimiter.spec.ts

@@ -119,4 +119,43 @@ describe(DefaultRateLimiter.name, () => {
       expect(parseFloat(rateLimiter["fillRate"].toFixed(6))).toEqual(fillRate);
     });
   });
+
+  describe("throttle detection via RetryErrorInfo.errorType", () => {
+    it("enables the rate limiter when errorType is THROTTLING", () => {
+      vi.spyOn(Date, "now").mockImplementation(() => 0);
+      const rateLimiter = new DefaultRateLimiter();
+      expect(rateLimiter["enabled"]).toBe(false);
+
+      vi.spyOn(Date, "now").mockImplementation(() => 1000);
+      rateLimiter.updateClientSendingRate({ errorType: "THROTTLING" });
+      expect(rateLimiter["enabled"]).toBe(true);
+    });
+
+    it("does not enable the rate limiter for non-throttling errorType", () => {
+      vi.spyOn(Date, "now").mockImplementation(() => 0);
+      const rateLimiter = new DefaultRateLimiter();
+
+      vi.spyOn(Date, "now").mockImplementation(() => 1000);
+      rateLimiter.updateClientSendingRate({ errorType: "TRANSIENT" });
+      expect(rateLimiter["enabled"]).toBe(false);
+    });
+
+    it("does not call isThrottlingError when errorType is present", () => {
+      vi.spyOn(Date, "now").mockImplementation(() => 0);
+      const rateLimiter = new DefaultRateLimiter();
+
+      vi.spyOn(Date, "now").mockImplementation(() => 1000);
+      rateLimiter.updateClientSendingRate({ errorType: "THROTTLING" });
+      expect(isThrottlingError).not.toHaveBeenCalled();
+    });
+
+    it("falls back to isThrottlingError when errorType is absent", () => {
+      vi.spyOn(Date, "now").mockImplementation(() => 0);
+      const rateLimiter = new DefaultRateLimiter();
+
+      vi.spyOn(Date, "now").mockImplementation(() => 1000);
+      rateLimiter.updateClientSendingRate({});
+      expect(isThrottlingError).toHaveBeenCalled();
+    });
+  });
 });

packages/util-retry/src/DefaultRateLimiter.ts

@@ -97,7 +97,7 @@ export class DefaultRateLimiter implements RateLimiter {
     let calculatedRate: number;
     this.updateMeasuredRate();
 
-    if (isThrottlingError(response)) {
+    if (this.isThrottlingResponse(response)) {
       const rateToUse = !this.enabled ? this.measuredTxRate : Math.min(this.measuredTxRate, this.fillRate);
       this.lastMaxRate = rateToUse;
       this.calculateTimeWindow();
@@ -113,6 +113,14 @@ export class DefaultRateLimiter implements RateLimiter {
     this.updateTokenBucketRate(newRate);
   }
 
+  private isThrottlingResponse(response: any): boolean {
+    if (response?.errorType) {
+      return response.errorType === "THROTTLING";
+    }
+    return isThrottlingError(response);
+  }
+
+
   private calculateTimeWindow() {
     this.timeWindow = this.getPrecise(Math.pow((this.lastMaxRate * (1 - this.beta)) / this.scaleConstant, 1 / 3));
   }