Backport retryable lb exchange filter function (#902)

Author: OlgaMaciaszek

README.adoc

@@ -27,7 +27,7 @@ Extract the files into the JDK/jre/lib/security folder for whichever version of
 
 == Building
 
-:jdkversion: 1.7
+:jdkversion: 1.8
 
 === Basic Compile and Test
 

docs/src/main/asciidoc/_configprops.adoc

@@ -33,6 +33,10 @@
 |spring.cloud.loadbalancer.health-check.refetch-instances | false | Indicates whether the instances should be refetched by the <code>HealthCheckServiceInstanceListSupplier</code>. This can be used if the instances can be updated and the underlying delegate does not provide an ongoing flux.
 |spring.cloud.loadbalancer.health-check.refetch-instances-interval | 25s | Interval for refetching available service instances.
 |spring.cloud.loadbalancer.health-check.repeat-health-check | true | Indicates whether health checks should keep repeating. It might be useful to set it to <code>false</code> if periodically refetching the instances, as every refetch will also trigger a healthcheck.
+|spring.cloud.loadbalancer.retry.backoff.enabled | false | Indicates whether Reactor Retry backoffs should be applied.
+|spring.cloud.loadbalancer.retry.backoff.jitter | 0.5 | Used to set {@link RetryBackoffSpec#jitter}.
+|spring.cloud.loadbalancer.retry.backoff.max-backoff |  | Used to set {@link RetryBackoffSpec#maxBackoff}.
+|spring.cloud.loadbalancer.retry.backoff.min-backoff | 5ms | Used to set {@link RetryBackoffSpec#minBackoff}.
 |spring.cloud.loadbalancer.retry.enabled | true | 
 |spring.cloud.loadbalancer.retry.max-retries-on-next-service-instance | 1 | Number of retries to be executed on the next <code>ServiceInstance</code>. A <code>ServiceInstance</code> is chosen before each retry call.
 |spring.cloud.loadbalancer.retry.max-retries-on-same-service-instance | 0 | Number of retries to be executed on the same <code>ServiceInstance</code>.

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

@@ -452,11 +452,67 @@ set the `spring.cloud.loadbalancer.ribbon.enabled` property to `false`.
 
 A load-balanced `RestTemplate` can be configured to retry failed requests.
 By default, this logic is disabled.
-You can enable it by adding link:https://github.com/spring-projects/spring-retry[Spring Retry] to your application's classpath.
+For the non-reactive version (with `RestTemplate`), you can enable it by adding link:https://github.com/spring-projects/spring-retry[Spring Retry] to your application's classpath.
+
+To use the reactive version of load-balanced retries in the Hoxton release train, you will need to instantiate your own `RetryableLoadBalancerExchangeFilterFunction` bean:
+
+[source,java,indent=0]
+----
+@Configuration
+public class MyConfiguration {
+
+	@Bean
+	RetryableLoadBalancerExchangeFilterFunction retryableLoadBalancerExchangeFilterFunction(
+			LoadBalancerRetryProperties properties,
+			ReactiveLoadBalancer.Factory<ServiceInstance> factory) {
+		return new RetryableLoadBalancerExchangeFilterFunction(
+				new RetryableExchangeFilterFunctionLoadBalancerRetryPolicy(
+						properties),
+				factory, properties);
+		}
+}
+----
+
+Then you can use it as a filter while building `webClient` instances:
+
+[source,java,indent=0]
+----
+public class MyClass {
+    @Autowired
+    private RetryableLoadBalancerExchangeFilterFunction retryableLbFunction;
+
+    public Mono<String> doOtherStuff() {
+        return WebClient.builder().baseUrl("http://stores")
+            .filter(retryableLbFunction)
+            .build()
+            .get()
+            .uri("/stores")
+            .retrieve()
+            .bodyToMono(String.class);
+    }
+}
+----
 
 If you would like to disable the retry logic with Spring Retry on the classpath, you can set `spring.cloud.loadbalancer.retry.enabled=false`.
 
-If you would like to implement a `BackOffPolicy` in your retries, you need to create a bean of type `LoadBalancedRetryFactory` and override the `createBackOffPolicy()` method.
+For the non-reactive implementation, if you would like to implement a `BackOffPolicy` in your retries, you need to create a bean of type `LoadBalancedRetryFactory` and override the `createBackOffPolicy()` method.
+
+For the reactive implementation, you just need to enable it by setting `spring.cloud.loadbalancer.retry.backoff.enabled` to `false`.
+
+You can set:
+
+- `spring.cloud.loadbalancer.retry.maxRetriesOnSameServiceInstance` - indicates how many times a request should be retried on the same `ServiceInstance` (counted separately for every selected instance)
+- `spring.cloud.loadbalancer.retry.maxRetriesOnNextServiceInstance` - indicates how many times a request should be retried a newly selected `ServiceInstance`
+- `spring.cloud.loadbalancer.retry.retryableStatusCodes` - the status codes on which to always retry a failed request.
+
+For the reactive implementation, you can additionally set:
+- `spring.cloud.loadbalancer.retry.backoff.minBackoff` - Sets the minimum backoff duration (by default, 5 milliseconds)
+- `spring.cloud.loadbalancer.retry.backoff.maxBackoff` - Sets the maximum backoff duration (by default, max long value of milliseconds)
+- `spring.cloud.loadbalancer.retry.backoff.jitter` - Sets the jitter used for calculationg the actual backoff duration for each call (by default, 0.5).
+
+For the reactive implementation, you can also implement your own `LoadBalancerRetryPolicy` to have more detailed control over the load-balanced call retries.
+
+WARN:: For the non-reactive version, if you chose to override the `LoadBalancedRetryFactory` while using the Spring Cloud LoadBalancer-backed approach, make sure you annotate your bean with `@Order` and set it to a higher precedence than `1000`, which is the order set on the `BlockingLoadBalancedRetryFactory`.
 
 ===== Ribbon-based retries
 
@@ -475,23 +531,6 @@ For the Spring Cloud LoadBalancer-backed implementation, you can set:
 
 WARN:: If you chose to override the `LoadBalancedRetryFactory` while using the Spring Cloud LoadBalancer-backed approach, make sure you annotate your bean with `@Order` and set it to a higher precedence than `1000`, which is the order set on the `BlockingLoadBalancedRetryFactory`.
 
-====
-[source,java,indent=0]
-----
-@Configuration
-public class MyConfiguration {
-    @Bean
-    LoadBalancedRetryFactory retryFactory() {
-        return new LoadBalancedRetryFactory() {
-            @Override
-            public BackOffPolicy createBackOffPolicy(String service) {
-        		return new ExponentialBackOffPolicy();
-        	}
-        };
-    }
-}
-----
-====
 
 NOTE: `client` in the preceding examples should be replaced with your Ribbon client's name.
 

spring-cloud-commons/src/main/java/org/springframework/cloud/client/loadbalancer/LoadBalancerRetryProperties.java

@@ -16,9 +16,12 @@
 
 package org.springframework.cloud.client.loadbalancer;
 
+import java.time.Duration;
 import java.util.HashSet;
 import java.util.Set;
 
+import reactor.util.retry.RetryBackoffSpec;
+
 import org.springframework.boot.context.properties.ConfigurationProperties;
 import org.springframework.http.HttpMethod;
 
@@ -54,6 +57,11 @@ public class LoadBalancerRetryProperties {
 	 */
 	private Set<Integer> retryableStatusCodes = new HashSet<>();
 
+	/**
+	 * Properties for Reactor Retry backoffs in Spring Cloud LoadBalancer.
+	 */
+	private Backoff backoff = new Backoff();
+
 	/**
 	 * Returns true if the load balancer should retry failed requests.
 	 * @return True if the load balancer should retry failed requests; false otherwise.
@@ -102,4 +110,68 @@ public void setRetryableStatusCodes(Set<Integer> retryableStatusCodes) {
 		this.retryableStatusCodes = retryableStatusCodes;
 	}
 
+	public Backoff getBackoff() {
+		return backoff;
+	}
+
+	public void setBackoff(Backoff backoff) {
+		this.backoff = backoff;
+	}
+
+	public static class Backoff {
+
+		/**
+		 * Indicates whether Reactor Retry backoffs should be applied.
+		 */
+		private boolean enabled = false;
+
+		/**
+		 * Used to set {@link RetryBackoffSpec#minBackoff}.
+		 */
+		private Duration minBackoff = Duration.ofMillis(5);
+
+		/**
+		 * Used to set {@link RetryBackoffSpec#maxBackoff}.
+		 */
+		private Duration maxBackoff = Duration.ofMillis(Long.MAX_VALUE);
+
+		/**
+		 * Used to set {@link RetryBackoffSpec#jitter}.
+		 */
+		private double jitter = 0.5d;
+
+		public Duration getMinBackoff() {
+			return minBackoff;
+		}
+
+		public void setMinBackoff(Duration minBackoff) {
+			this.minBackoff = minBackoff;
+		}
+
+		public Duration getMaxBackoff() {
+			return maxBackoff;
+		}
+
+		public void setMaxBackoff(Duration maxBackoff) {
+			this.maxBackoff = maxBackoff;
+		}
+
+		public double getJitter() {
+			return jitter;
+		}
+
+		public void setJitter(double jitter) {
+			this.jitter = jitter;
+		}
+
+		public boolean isEnabled() {
+			return enabled;
+		}
+
+		public void setEnabled(boolean enabled) {
+			this.enabled = enabled;
+		}
+
+	}
+
 }

spring-cloud-commons/src/main/java/org/springframework/cloud/client/loadbalancer/RetryableRequestContext.java

@@ -0,0 +1,79 @@
+/*
+ * Copyright 2012-2021 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.cloud.client.loadbalancer;
+
+import java.util.Objects;
+
+import org.springframework.cloud.client.ServiceInstance;
+import org.springframework.core.style.ToStringCreator;
+
+/**
+ * A request context object that allows storing information on previously used service
+ * instances.
+ *
+ * @author Olga Maciaszek-Sharma
+ * @since 2.2.7
+ */
+public class RetryableRequestContext extends DefaultRequestContext {
+
+	private ServiceInstance previousServiceInstance;
+
+	public RetryableRequestContext(ServiceInstance previousServiceInstance) {
+		this.previousServiceInstance = previousServiceInstance;
+	}
+
+	public RetryableRequestContext(ServiceInstance previousServiceInstance, String hint) {
+		super(hint);
+		this.previousServiceInstance = previousServiceInstance;
+	}
+
+	public ServiceInstance getPreviousServiceInstance() {
+		return previousServiceInstance;
+	}
+
+	public void setPreviousServiceInstance(ServiceInstance previousServiceInstance) {
+		this.previousServiceInstance = previousServiceInstance;
+	}
+
+	@Override
+	public String toString() {
+		ToStringCreator to = new ToStringCreator(this);
+		to.append("previousServiceInstance", previousServiceInstance);
+		return to.toString();
+	}
+
+	@Override
+	public boolean equals(Object o) {
+		if (this == o) {
+			return true;
+		}
+		if (!(o instanceof RetryableRequestContext)) {
+			return false;
+		}
+		if (!super.equals(o)) {
+			return false;
+		}
+		RetryableRequestContext context = (RetryableRequestContext) o;
+		return Objects.equals(previousServiceInstance, context.previousServiceInstance);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(super.hashCode(), previousServiceInstance);
+	}
+
+}

spring-cloud-commons/src/main/java/org/springframework/cloud/client/loadbalancer/reactive/ExchangeFilterFunctionUtils.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2012-2021 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.cloud.client.loadbalancer.reactive;
+
+import java.net.URI;
+
+import org.springframework.web.reactive.function.client.ClientRequest;
+import org.springframework.web.reactive.function.client.ExchangeFilterFunction;
+
+/**
+ * A utility class for load-balanced {@link ExchangeFilterFunction} instances.
+ *
+ * @author Olga Maciaszek-Sharma
+ * @since 2.2.7
+ */
+public final class ExchangeFilterFunctionUtils {
+
+	private ExchangeFilterFunctionUtils() {
+		throw new IllegalStateException("Can't instantiate a utility class.");
+	}
+
+	static ClientRequest buildClientRequest(ClientRequest request, URI uri) {
+		return ClientRequest.create(request.method(), uri)
+				.headers(headers -> headers.addAll(request.headers()))
+				.cookies(cookies -> cookies.addAll(request.cookies()))
+				.attributes(attributes -> attributes.putAll(request.attributes()))
+				.body(request.body()).build();
+	}
+
+}