Add Retry After header

src/http.ts

@@ -107,7 +107,7 @@ export async function doHttpRequest(
     if (typeof (errBody) === "object" && 'errcode' in errBody) {
         const redactedBody = respIsBuffer ? '<Buffer>' : redactObjectForLogging(errBody);
         LogService.error("MatrixHttpClient", "(REQ-" + requestId + ")", redactedBody);
-        throw new MatrixError(errBody, response.statusCode);
+        throw new MatrixError(errBody, response.statusCode, response.headers);
     }
 
     // Don't log the body unless we're in debug mode. They can be large.

src/models/MatrixError.ts

@@ -1,8 +1,26 @@
+import { LogService } from "../logging/LogService";
+
 /**
  * Represents an HTTP error from the Matrix server.
  * @category Error handling
  */
 export class MatrixError extends Error {
+    /**
+     * Parse a Retry-After header into a number of milliseconds.
+     * @see https://www.rfc-editor.org/rfc/rfc9110#field.retry-after
+     * @param header The value of a Retry-After header.
+     * @throws If the date could not be parsed.
+     */
+    static parseRetryAfterHeader(header: string): number {
+        // First try to parse as seconds
+        const retryAfterSeconds = parseInt(header, 10);
+        if (!Number.isNaN(retryAfterSeconds)) {
+            return retryAfterSeconds * 1000;
+        }
+        const retryAfterDate = new Date(header);
+        return retryAfterDate.getTime() - Date.now();
+    }
+
     /**
      * The Matrix error code
      */
@@ -23,11 +41,23 @@ export class MatrixError extends Error {
      * @param body The error body.
      * @param statusCode The HTTP status code.
      */
-    constructor(public readonly body: { errcode: string, error: string, retry_after_ms?: number }, public readonly statusCode: number) {
+    constructor(public readonly body: { errcode: string, error: string, retry_after_ms?: number }, public readonly statusCode: number, headers: Record<string, string>) {
         super();
         this.errcode = body.errcode;
         this.error = body.error;
-        this.retryAfterMs = body.retry_after_ms;
+        const retryAfterHeader = headers['retry-after'];
+        if (this.statusCode === 429 && retryAfterHeader) {
+            try {
+                this.retryAfterMs = MatrixError.parseRetryAfterHeader(retryAfterHeader);
+            } catch (ex) {
+                // Could not parse...skip handling for now.
+                LogService.warn("MatrixError", "Could not parse Retry-After header from request.", ex);
+            }
+        }
+        // Fall back to the deprecated retry_after_ms property.
+        if (!this.retryAfterMs && body.retry_after_ms) {
+            this.retryAfterMs = body.retry_after_ms;
+        }
     }
 
     /**

test/models/MatrixErrorTest.ts

@@ -0,0 +1,39 @@
+import { MatrixError } from "../../src";
+
+describe("MatrixError", () => {
+    it("should construct a basic MatrixError", () => {
+        const err = new MatrixError({ 'errcode': 'M_TEST', "error": 'Test fail' }, 500, {});
+        expect(err.message).toBe('M_TEST: Test fail');
+        expect(err.retryAfterMs).toBeUndefined();
+    });
+    it("should handle a 429 without a retry duration", () => {
+        const err = new MatrixError({ 'errcode': 'M_TEST', "error": 'Test fail' }, 429, {});
+        expect(err.message).toBe('M_TEST: Test fail');
+        expect(err.retryAfterMs).toBeUndefined();
+    });
+    it("should handle a 429 with a Retry-After header (time)", () => {
+        // Should ignore the deprecated field.
+        const err = new MatrixError({ 'errcode': 'M_TEST', "error": 'Test fail', "retry_after_ms": 5 }, 429, {
+            'retry-after': '10',
+        });
+        expect(err.message).toBe('M_TEST: Test fail');
+        expect(err.retryAfterMs).toEqual(10000);
+    });
+    it("should handle a 429 with a Retry-After header (date)", () => {
+        jest
+            .spyOn(global.Date, 'now')
+            .mockImplementationOnce(() => new Date('Wed, 20 Mar 2024 10:18:16 UTC').valueOf());
+
+        // Should ignore the deprecated field.
+        const err = new MatrixError({ 'errcode': 'M_TEST', "error": 'Test fail', "retry_after_ms": 5 }, 429, {
+            'retry-after': 'Wed, 20 Mar 2024 10:18:26 UTC',
+        });
+        expect(err.message).toBe('M_TEST: Test fail');
+        expect(err.retryAfterMs).toEqual(10000);
+    });
+    it("should handle a 429 with a Retry-After header (date)", () => {
+        const err = new MatrixError({ 'errcode': 'M_TEST', "error": 'Test fail', "retry_after_ms": 5 }, 429, {});
+        expect(err.message).toBe('M_TEST: Test fail');
+        expect(err.retryAfterMs).toEqual(5);
+    });
+});