Add support for random exponential backoff policy. Fixes #2351 (#2353)

Co-authored-by: Ryan Baxter <[email protected]>

docs/src/main/asciidoc/spring-cloud-config.adoc

@@ -1906,6 +1906,7 @@ First, you need to set `spring.cloud.config.fail-fast=true`.
 Then you need to add `spring-retry` and `spring-boot-starter-aop` to your classpath.
 The default behavior is to retry six times with an initial backoff interval of 1000ms and an exponential multiplier of 1.1 for subsequent backoffs.
 You can configure these properties (and others) by setting the `spring.cloud.config.retry.*` configuration properties.
+To use a random exponential backoff policy set `spring.cloud.config.retry.useRandomPolicy` to `true`.
 
 TIP: To take full control of the retry behavior and are using legacy bootstrap, add a `@Bean` of type `RetryOperationsInterceptor` with an ID of `configServerRetryInterceptor`.
 Spring Retry has a `RetryInterceptorBuilder` that supports creating one.

spring-cloud-config-client/src/main/java/org/springframework/cloud/config/client/RetryProperties.java

@@ -50,6 +50,11 @@ public class RetryProperties {
 	 */
 	int maxAttempts = 6;
 
+	/**
+	 * Use a random exponential backoff policy.
+	 */
+	boolean useRandomPolicy = false;
+
 	public long getInitialInterval() {
 		return this.initialInterval;
 	}
@@ -82,4 +87,12 @@ public void setMaxAttempts(int maxAttempts) {
 		this.maxAttempts = maxAttempts;
 	}
 
+	public boolean isUseRandomPolicy() {
+		return this.useRandomPolicy;
+	}
+
+	public void setUseRandomPolicy(boolean useRandomPolicy) {
+		this.useRandomPolicy = useRandomPolicy;
+	}
+
 }

spring-cloud-config-client/src/main/java/org/springframework/cloud/config/client/RetryTemplateFactory.java

@@ -39,9 +39,9 @@ private RetryTemplateFactory() {
 	}
 
 	public static RetryTemplate create(RetryProperties properties, Log log) {
-		RetryTemplate retryTemplate = RetryTemplate.builder().maxAttempts(properties.getMaxAttempts())
-				.exponentialBackoff(properties.getInitialInterval(), properties.getMultiplier(),
-						properties.getMaxInterval())
+		RetryTemplate retryTemplate = RetryTemplate
+				.builder().maxAttempts(properties.getMaxAttempts()).exponentialBackoff(properties.getInitialInterval(),
+						properties.getMultiplier(), properties.getMaxInterval(), properties.isUseRandomPolicy())
 				.build();
 		try {
 			field.set(retryTemplate, log);

spring-cloud-config-client/src/test/java/org/springframework/cloud/config/client/ConfigServerConfigDataLocationResolverTests.java

@@ -138,6 +138,7 @@ void retryPropertiesShouldBeDefaultByDefault() {
 		assertThat(resource.getRetryProperties().getMaxInterval()).isEqualTo(defaultRetry.getMaxInterval());
 		assertThat(resource.getRetryProperties().getInitialInterval()).isEqualTo(defaultRetry.getInitialInterval());
 		assertThat(resource.getRetryProperties().getMultiplier()).isEqualTo(defaultRetry.getMultiplier());
+		assertThat(resource.getRetryProperties().isUseRandomPolicy()).isEqualTo(defaultRetry.isUseRandomPolicy());
 	}
 
 	@Test
@@ -158,6 +159,7 @@ void uriWithParamsParsesProperties() {
 		assertThat(resource.getRetryProperties().getMaxInterval()).isEqualTo(1500);
 		assertThat(resource.getRetryProperties().getInitialInterval()).isEqualTo(1100);
 		assertThat(resource.getRetryProperties().getMultiplier()).isEqualTo(1.2);
+		assertThat(resource.getRetryProperties().isUseRandomPolicy()).isEqualTo(false);
 	}
 
 	@Test