[core-amqp] Implement exponential retry mechanism

sdk/core/core-amqp/src/index.ts

@@ -4,7 +4,7 @@
 /// <reference lib="es2015" />
 
 export { RequestResponseLink, SendRequestOptions } from "./requestResponseLink";
-export { retry, RetryConfig, RetryOperationType } from "./retry";
+export { retry, RetryConfig, RetryOperationType, RetryPolicy } from "./retry";
 export { DataTransformer, DefaultDataTransformer } from "./dataTransformer";
 export { TokenType } from "./auth/token";
 export { AccessToken, TokenCredential, isTokenCredential } from "@azure/core-auth";

sdk/core/core-amqp/src/retry.ts

@@ -4,7 +4,12 @@
 import { translate, MessagingError } from "./errors";
 import { delay, isNode } from "./util/utils";
 import * as log from "./log";
-import { defaultMaxRetries, defaultDelayBetweenRetriesInSeconds } from "./util/constants";
+import {
+  defaultMaxRetries,
+  defaultDelayBetweenOperationRetriesInSeconds,
+  defaultMaxDelayForExponentialRetryInMs,
+  defaultMinDelayForExponentialRetryInMs
+} from "./util/constants";
 import { resolve } from "dns";
 
 /**
@@ -25,6 +30,15 @@ function isDelivery(obj: any): boolean {
   return result;
 }
 
+/**
+ * Describes the RetryPolicy type
+ * @enum RetryPolicy
+ */
+export enum RetryPolicy {
+  ExponentialRetryPolicy,
+  LinearRetryPolicy
+}
+
 /**
  * Describes the retry operation type.
  * @enum RetryOperationType
@@ -66,14 +80,30 @@ export interface RetryConfig<T> {
   maxRetries?: number;
   /**
    * @property {number} [delayInSeconds] Amount of time to wait in seconds before making the
-   * next attempt. Default: 15.
+   * next attempt. Default: 30.
+   * When `retryPolicy` option is set to `ExponentialRetryPolicy`, \
+   * this is used to compute the exponentially increasing delays between retries.
    */
   delayInSeconds?: number;
   /**
    * @property {string} connectionHost The host "<yournamespace>.servicebus.windows.net".
    * Used to check network connectivity.
    */
   connectionHost?: string;
+  /**
+   * @property {RetryPolicy} [retryPolicy] Denotes which retry policy to apply. Default is `LinearRetryPolicy`
+   */
+  retryPolicy?: RetryPolicy;
+  /**
+   * @property {number} [maxExponentialRetryDelayInMs] Denotes the maximum delay between retries
+   * that the retry attempts will be capped at. Applicable only when performing exponential retry.
+   */
+  maxExponentialRetryDelayInMs?: number;
+  /**
+   * @property {number} [minExponentialRetryDelayInMs] Denotes the minimum delay between retries
+   * to use. Applicable only when performing exponential retry.
+   */
+  minExponentialRetryDelayInMs?: number;
 }
 
 /**
@@ -115,10 +145,13 @@ async function checkNetworkConnection(host: string): Promise<boolean> {
  * The number of additional attempts is governed by the `maxRetries` property provided
  * on the `RetryConfig` argument.
  *
- * The retries when made are done so linearly on the given operation for a specified number of times,
- * with a specified delay in between each retry.
+ * If `retryPolicy` option is set to `LinearRetryPolicy`, then the retries when made are done so linearly on the
+ * given operation for a specified number of times, with a specified delay in between each retry.
+ *
+ * If `retryPolicy` option is set to `ExponentialRetryPolicy`, then the delay between retries is adjusted to increase
+ * exponentially with each attempt using back-off factor of power 2.
  *
- * @param {RetryConfig<T>} config Parameters to configure retry operation.
+ * @param {RetryConfig<T>} config Parameters to configure retry operation
  *
  * @return {Promise<T>} Promise<T>.
  */
@@ -128,7 +161,13 @@ export async function retry<T>(config: RetryConfig<T>): Promise<T> {
     config.maxRetries = defaultMaxRetries;
   }
   if (config.delayInSeconds == undefined || config.delayInSeconds < 0) {
-    config.delayInSeconds = defaultDelayBetweenRetriesInSeconds;
+    config.delayInSeconds = defaultDelayBetweenOperationRetriesInSeconds;
+  }
+  if (config.maxExponentialRetryDelayInMs == undefined || config.maxExponentialRetryDelayInMs < 0) {
+    config.maxExponentialRetryDelayInMs = defaultMaxDelayForExponentialRetryInMs;
+  }
+  if (config.minExponentialRetryDelayInMs == undefined || config.minExponentialRetryDelayInMs < 0) {
+    config.minExponentialRetryDelayInMs = defaultMinDelayForExponentialRetryInMs;
   }
   let lastError: MessagingError | undefined;
   let result: any;
@@ -174,14 +213,28 @@ export async function retry<T>(config: RetryConfig<T>): Promise<T> {
         i,
         err
       );
+      let targetDelayInMs = config.delayInSeconds;
+      if (config.retryPolicy === RetryPolicy.ExponentialRetryPolicy) {
+        let incrementDelta = Math.pow(2, i) - 1;
+        const boundedRandDelta =
+          config.delayInSeconds * 0.8 +
+          Math.floor(Math.random() * (config.delayInSeconds * 1.2 - config.delayInSeconds * 0.8));
+        incrementDelta *= boundedRandDelta;
+
+        targetDelayInMs = Math.min(
+          config.minExponentialRetryDelayInMs + incrementDelta,
+          config.maxExponentialRetryDelayInMs
+        );
+      }
+
       if (lastError && lastError.retryable) {
         log.error(
           "[%s] Sleeping for %d seconds for '%s'.",
           config.connectionId,
-          config.delayInSeconds,
+          targetDelayInMs / 1000,
           config.operationType
         );
-        await delay(config.delayInSeconds * 1000);
+        await delay(targetDelayInMs);
         continue;
       } else {
         break;

sdk/core/core-amqp/src/util/constants.ts

@@ -75,8 +75,9 @@ export const aadTokenValidityMarginSeconds = 5;
 export const connectionReconnectDelay = 300;
 export const defaultMaxRetries = 3;
 export const defaultMaxRetriesForConnection = 150;
-export const defaultDelayBetweenOperationRetriesInSeconds = 5;
-export const defaultDelayBetweenRetriesInSeconds = 15;
+export const defaultDelayBetweenOperationRetriesInSeconds = 30;
+export const defaultMaxDelayForExponentialRetryInMs = 1000 * 90;
+export const defaultMinDelayForExponentialRetryInMs = 1000 * 3;
 export const receiverSettleMode = "receiver-settle-mode";
 export const dispositionStatus = "disposition-status";
 export const fromSequenceNumber = "from-sequence-number";